F BULLETIN NO. 693 TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS, Director College Station, Texas SEPTEMBER 1947 Nitrification Capacities of Texas Soil Types and Factors which Aflect Nitrification G. S. FRAPS and A. J. STERGES AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS GIBB GILCHRIST, President J12-1047-3M-L180 [Blank Page in Original Bulletin] Preface Nitrification is the process which changes organic matter and am- , monia in the soil t0 nitrates. Nitrates are readily used as plant food, are also easily soluble in water and can be leached from the soil. The nitrifying capacities of soils for ammonium sulphate may range from o to 100 percent but additions of bacteria and calcium carbonate will increase the nitrifying capacities of most soils and subsoils to a high extent. Soils with low nitrification capacities have 10w nitrogen content, low basicity and are slightly acid or neutral. Soils with high nitri- . lying capacities usually contain more than .06 percent nitrogen, have basicities greater than 0.6 percent and pH values higher than 7. Upland surface soil types of East Texas and other non-calcareous soils have low nitrifying capacities. Upland calcareous soil types have high nitrifying capacities. N itrification ofmjgmt/ormiggmpprcent of themspil 1l2§ days 0f_in¢17@3i@715i§f5@ consideréiiEfiTfiriial for SQijjL1QPF1III11H8i-Q5. Petrscenfi. ,0? _.II3.Q1K¢.-.Q£-.H.1.§¥9%§H- The number of nitrate and nitrite-forming organisms are in gen- eral related to nitrification but the relations are not consistent. Ni- trites produced during nitrification are not always completely oxi- dized in nitrates, especially if insufficient numbers of nitrate-forming organisms are present at the beginning of the nitrification. The con- version of nitrites to nitrates in soil is almost completely a biological process. p Nitrification is decreased b puddling of soils, and/Goes not occur to an appreciable extent i ater-logged soils. In soils of high nitri- fying capacity, the nitrogen of cottonseed meal is nitrified to the F average extent of 5o percent of that of ammonium sulphate, but in 1_soils of low nitrifying capacity, nitrogen of cottonseed meal may be J nitrified more readily than that of ammonium sulphate. When the I fertilizing values of organic nitrogenous fertilizers are to be compared by means ofinitrification experiments, soils of high nitrifying capacity Ilegeairlg sff£2£S,9i.§mne .add¢d qtrsarais-tnatt@r “Pifllliilificfltifm _~may persist for 20 weelis,“ Cyanamid is not readilymriitrified and de- [presses nitrTifi hen applied at the rate of more than 10o parts of nitrogen per million of soil. The depressing effects of cyanamid Lpersisted 6 to 1o months, and the substances which interfered diffused Bvhen placed in one spot in the culture. Ground sulphur interferes _with nitrification, but probably not sufficiently to be of significance jin cultivated soils. The maximum amounts of nitric nitrogen in 2 lfield soils were found in July, October and April. CONTENTS Eflfect of Additions of Bacteria and Calcium Carbonate on Texas Soils ..‘I ation of Nitrifying Capacity of Inoculated Soils to Amount of Nitro- ‘ ge ; Basicity and pH of the Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . trifying Capacities of Texas Soil Types . . . . . . . . . . . . . . . . . . . . . . . . . Efl"ect of Bacteria and Calcium Carbonate on Nitrification of tll Soil Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._ . . . . . . . . . . Numbers of Organisms as Related to Nitrification . . . . . . . . . . . . . . . Occurrence of Nitrites in Experimental Cultures . . . . . . . . . . . . . . . . . . Biological and Chemical Conversionof Nitrites to Nitrates . . . . . . . Effect of Sunlight on Nitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Elfect of Water Content, Puddling and Water-logging on Nitrificati Nitrification of Ammonium Salts of Organic Acids . . . . . . . . . . . . . . . . .., Nitrification of Cottonseed: Meal \. .. ._. . . . . . . . . . . . . . . . . . . . . . . . . . . . Persistence of Etfects of Addled Organic »Matter on Oxidation Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “A Nitrification of Cyanamid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ditfusion of Toxic Substances of Cyanamid . . . . . . . . . . . . . . . . . . . Elfect of Sulphur on Nitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effects of Phosphorus, Magnesium and Iron on Nitrification . . . in .’ 4 ‘Nitrification and Nitrifying Organisms in Two Field Soils During Vari Seasons c‘ ¢ ¢ o o Q n o Q e Q o | n o n n o » a u n Q u n Q Q Q u - u o o » u o ~ o Q Q u ¢ e ¢ n n ¢ u o a o a u an; Summary . . . . . . . . . . . . . . . . Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . c Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 . = .7... .",....,,.., , z BULLETIN NO. 693 SEPTEMBER 1947 . Nitrification Capacities of Texassoil Types, and Factors which Aflcct Nitrification G. S. FRAPS, Collaborating Chemist,* and A. J. STERGES, formerly Assistant Chemist“ -——7~w.—wm~w-_-rv» - - ~ The nitrogen in soils occurs chiefly in the form of organic com- pounds. A small fraction may be present as ammonia or as nitrates, and more rarely as nitrites. The organic compounds are only slightly soluble in water, and retain the nitrogen. ,The nitrogen is released for the use of plants by the gradual. decomposition of the ; organic compounds. The organic compounds, among other uses, serve to store nitrogen so as to avoid rapid depletion of the nitrogen ‘ of the soil. Many changes take place in the nitrogen of the soil. These are brought about by bacteria and other living organisms. There is, r first, the transformation of organic nitrogen into ammonia, termed ammonification. The ammonia is changed to nitrites. Nitrites are _. then changed to nitrates. This process is called nitrification. Ni- trites or nitrates may be decomposed to produce free nitrogen, a change called denitrification, or they may be used by microscopic organisms to form protein and, thereby, again become a part of the - organic matter of the soil. Nitrogen of the air may be fixed as protein, 1 either by organisms in the soil or, to a greater extent, by organisms Twhich live in nodules on the roots of leguminous plants. g Nitrates and ammonia are taken up by plants and are the chief ’ sources of the nitrogen in plants, with the exception of the nitrogen ‘of the air taken up by legumes. Since nitrates are the chief form i in which nitrogenous plant food is provided by soils, or provided by i organic fertilizers, or by manures added to soils, the changes of the i forms of nitrogen in the soil have been the subject of a large num- ber of investigations. No attempt will be made here to review all § the literature. A review has been made by Waksman (74). Nitrification in Texas soils, as the subject of a project, was studied for several years, and a number of publications were made giving . *Retired July 31, 1947. * , **Now research chemist, Tennessee Valley Authority Agricultural Exper- iment Station, Knoxville, Tennessee. 6 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION the results of the Work (17-36 inclusive). This publication includes additional work which was not published at the time the project wa discontinued a few years ago. ’ In order to conserve space, detailed tables for some of the work are not given. Methods The samples used were taken for chemical analysis or for pot experiments from representative Texas soil types or areas. The samples were air dried and passed through a 6-mesh sieve after pounding up with a wooden pestle in a wooden box. Smaller sam- ples were passed through a I millimeter (1n.m.) sieve. The average chemical composition of.soil types of Texas is dis- cussed in Texas Station Bulletin No. 549 (26). ' In the nitrification tests (28), I00 grams of dry soil was mixed in a porcelain dish with the necessary additions. Water was next added to bring the total water content to 50 percent of the water- capacity of the soil. The soil was mixed with the water and with any other additions by cutting in with a spatula. The mixtures were transferred to I50 cubic centimeter (c.c.) beakers and kept at 35° C. in an incubator, water being added twice a week to restore the loss in weight. After days, the nitrates were estimated by the phenol-disulphonic acid method and the nitrites by the alpha- naphthylamine method (29). The results are expressed in parts per million (p.p.m.) of the dry soil. In many experiments the amount L? i i. e i. _ _44 _..v.-mm - ~ ' 'a.»m..m....¢.._._..s__.-.. . of the" nitrous nitrogen was small and, when not otherwise stated, ' i it is included with the amount of nitric nitrogen. When added, the amount of calcium carbonate was usually 1 gram, equal to I percent of the amount of soil taken. Bacteria were sometimes added by means of an inoculating liquid (Io c.c.). Am- moniurn sulphate, when added, was usually in 5 c.c. of a solution, containing 0.05 grams nitrogen, equal to 500 p.p.m. of the soil used. When other nitrogenous compounds were used, the same amount of nitrogen s usually added. To prepare the" oculating liquid, portions of actively nitrifying soil equivalent t Water was added gradually to form a thin paste, the suspension was transferred to a 500 c.c. flask, and made up to volume. just before withdrawing the inoculating liquid, the contents of the flask were thoroughly shaken. The inoculating liquid in much of the work was prepared from special cultures. To I00 grams of soil of high nitrifying capacity, ammonium sulphate, inoculating liquid and water were added as described above. After incubating 3% to IO grams of dry soil were ground in a mortar» ._l.._._...¢,......._“.._-...;..l~;_.n.;‘ ' . NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 7 4% weeks, these cultures were used to prepare the inoculating liquid. With such inoculating liquid, the nitrogen was usually oxidized to ‘a? nitrates; nitrites were either absent or present in very small amounts ' at the end of the experiment. Basicity was determined after adding 100 c.c. of o.2N nitric acid to 1o grams of soil, allowing the mixture to stand 3o minutes T or stirring it I 5 minutes, filtering, diluting IO c.c. with water, I‘ heating to remove carbon dioxide, and then titrating with o.1N ~ sodium hydroxide, using phenolphthalein as an indicator. If more than 8o percent of the acid was consumed, the test was repeated ' with the use of normal nitric acid. Basicity is expressed in terms § of percentage of calcium carbonate.. The acid was neutralized chiefly - by calcium derived from calcium carbonate, if present, from calcium in the base exchange complex and from silicates decomposed by » the acid (25). To determine the water capacity, 5o grams of dry soil, pounded up to pass a 10-mesh sieve, was placed on a porcelain filter plate in a carbon filter tube 1% inches in diameter. Water was added if gradually until the soil was saturated and a little had run through. The tube was then covered and allowed to drain 3o minutes. The a stem of the tube was ‘dried with filter paper and the tube weighed. 1 Water capacity is expressed in percentage of the dry soil. The numbers of the organisms which convert ammonia to nitrite, 1 and those which convert nitrites to nitrates were determined by the ‘dilution method. Vessels plugged with cotton wool and utensils were sterilized at 140° C. for 2 hours. Distilled water was boiled f I hour. Suspensions of different strength of the soil were inocu- lated into suitable sterilized culture media in I25 c.c. Erlenmeyer flasks, incubated 28 days at 35° C. and then tested for nitrates or nitrites. The medium for determining the number of the nitrite-forming i organisms consisted of 50 c.c. of distilled water in a I25 c.c. Erlen- meyer flask, .5 grams of calcium carbonate, I c.c. of ammonium 4 sulphate containing .01 gram nitrogen and 5 c.c. of mineral solu- tion. The mineral solution contained I gram dipotassium phosphate, .5 gram magnesium sulphate and .4 gram ferrous sulphate in 500 -ic.c. of water. Five cultures were inoculated with 5 c.c. and 5 1 with IO c.c. of each soil suspension used. After inoculation and 3 incubation for 28 days, nitrites were determined by the alpha- ‘ naphthylamine method (29). From the number of cultures which when inoculated with the more dilute soil suspension gave positive tests for nitrites, the num- ber of nitrifying organisms was estimated. 8 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION For nitrate-forming bacteria, the medium consisted of 5o c.c. distilled water, 5 c.c. lime water, 5 c.c. of the mineral nutrient used for the nitrate forming organisms, and 5 c.c. sodium nitrite solu- tionlcontaining .OI gram nitrite nitrogen made from silver nitrite (29). After incubation for 28 days, nitrates were determined quan- " titatively with the phenol-disulphonic acid method (29). The quan- ptitative determination was necessary because chemical oxidation of nitrites produced small amounts of nitrates in some of the cultures. To prepare soil suspensions, soil equal to 10 grams of air-dry soil was ground in a mortar with small quantities of sterilized water, and sterilized water was added gradually until a thin paste was‘ formed. The mixture was transferred to a 500 c.c. flask, and made up to volume (suspension A). Suspension B consisted of IO c.c. of A diluted to 250 c.c.; Suspension C, of I0 c.c. of B diluted to 20o c.c.; Suspension D, of IO c.c. of C diluted to 200 c.c.; Suspen- sion E, of Io c.c. of D diluted to 200 c.c. In preliminary work, 3o flasks were used for each sample of soil, and 5 of each were inocu- lated with I c.c. or 5 c.c. of suspensions A, B and C respectively. That the liquid media were satisfactory was shown by complete oxidation of ammonia or nitrites when suflicient numbers of bacteria were added. A When 5 flasks are inoculated with 5 c.c. of dilution A, they re- ceive a total of .5 gram soil. If one of the 5 flasks gives a positive test for nitrate or nitrite-forming bacteria, there is I bacteria or clump of bacteria in .5 gram soil, which is 2 bacteria per I gram . of soil. If all 5 flasks give positive tests, there are IO or more - bacteria per I gram of soil. With I c.c. of dilution A per flask, I flask of the 5 with a positive test means IO bacteria per I gram of soil; 5 positive tests means 5o per I gram. With 5 c.c. of dilu- tion B, I of 5 flasks with a positive test means 5o bacteria per I gram; 5 flasks with a positive test means 250 per I gram. With I c.c. of dilution B, I of the 5 flasks with a positive test means 25o bacteria per gram; 5 flasks means 1,250. With 5 c.c. of dilution C, I positive flask means 1,000 bacteria per gram; with 5 flasks, 5,000 per gram. With I c.c. of dilution C, I positive flask means 5,000 bacteria or clumps of bacteria per I gram of soil; 5 positive flasks mean 25,000 bacteria or clumps of bacteria per gram. And so on to higher dilutions, if necessary. To count the numbers of soil bacteria suitable suspensions of the soil were mixed with albumin agar plated in Petri dishes, and the number of colonies were counted which appeared after incubation (74, P1115613)- u-‘uf _ hL,z~4d;><_‘.-nflluw.imkiflfiriau.mz 1....» . I‘. _.- - Immmimuummaw W» ' ' l NITRIFICAHON CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. '9 The numbers of the autotrophic and the heterotrophic organisms" were estimated by plating, using silica gel with inorganic or organic media (64). Etfect of Additions of Bacteria and Calcium Carbonate on Texas Soils Soils vary widely in their capacity to nitrify ammonium sulphate. With some soils, additions of ammonium sulphate followed by‘ in- cubation results in the production of less nitrates than are produced in the original soil. With other soils, the nitrification ranges from nearly zero to almost complete conversion of the ammonia ‘to ni- trates in the period of 28 days. Fraps and Sterges (30,) found that additions of nitrifying soil, or of calcium carbonate, or of both calcium carbonate and nitrifying soil to soils of low nitrifying capacity would result in high nitrification of ammonium sulphate in many soils. In other words, the low nitrification of ammonium sulphate was due to deficiencies of nitrifying organisms, or of basic compounds needed t0 neutralize the nitric and sulphuric acids pro- duced, or of both. A few soils needed additions of available phos- phates for high nitrification ( 3 5) and there was a small percentage . left which still did not nitrify the ammonium sulphate completely. The object of the work here presented was to ascertain the nitri- fying capacity of Texas soil types and the effect of addition of bacteria and calcium carbonate on them. For this purpose, after preliminary work, 8 cultures were usually prepared for each sample of soil, as follows: (1) no addition, (2) addition of calcium car- bonate, (3) inoculating liquid, (4) calcium carbonate and inocu- lating liquid, (5) ammonium sulphate, (6) ammonium sulphate ‘ and calcium carbonate, (7) ammonium sulphate and inoculating l liquid, and (8) ammonium sulphate, calcium carbonate and inocu- , lating liquid. The nitrification of the ammonium sulphate was ascertained by substracting the quantity of nitric nitrogen inithe ‘ culture which did not receive ammonium sulphate from the quantity in corresponding culture which received ammonium sulphate. A summary of the effects of the inoculating liquid, the calcium ‘ carbonate, and of the two combined is given in Table 1. The soils were divided into groups according to the quantities of nitric nitro- v gen produced in the original soil which had received ammonium sulphate, namely, 0-25, 26-99, 101-199, 201-299, 300-399, andover 400 parts per million. The table shows the percentages of the num- bers of soils in each group in which_the nitrification was such as to move the soil to a higher or lower group, or leave it in the same group. For example, in the group originally nitrifying 0-25 p.p.m., 10 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION _ 1 zi= fifa . ..1.i.,i.._ --...-.- -. ..- -- ..-..-..-.. -.. . ~.- .-..-.-.- -- ..-. -.~ .-.- ..--Q_1°Q§=@N§qonvfl%hnwm$@flnxa$qhu>°flh°wfianv€whfi@cxfinhaulwho Nu mm mw w“ w» av 5 =3. ww Na m5 an Nu mu Q QN Q Q Q Qm ........................-E.Q.QQQN|QQN QGQEQNQuuaQPQQ mzomnum 2 .5855 a E .555 amwlccw :E5E=.E: 5:520 cw o nu w» an ow 5 ca“. 1N on ma on : an w ow w h 3. cu w vu o c u; c .. . .........................5.n.aam~|c¢~ 5o55955C< . E5515 2 62:...» 2 E .555 23.2w :o:auE.E: 1.5.x. cw n 3. w» av a .................o:o5 5 e3. cu > an vs w~ a .. . . . . . Imwwlcaw an c n a a nu .. h 0Q QN Q RN QQ .. . ........................-E.fl.fiflm~|QQmaG0E~§Q.-a hfic¢ Enema-i an éufirim : E .55.: 2:12: :E5uc_._2: 5:510 wm A: m 2 an e .. . . . . . ......o.55 .5 o3. an cw 2 aw vm c I. ............aan|=ew A: cu a w m: w .. m E S." w c En fi = x .-. -.--...-.-...--...iuau§$$ul@x flnnwgflfiQhahwfib€ 2:35am 2 .oua.~.5u 2 :5 .55.: aa-wu :Q=5E.E: ifiuto an c w wu w o .. .5 =3. wu w w ww 2 c .........................amn|oew wu a 2 ow an c .. ww Eu z v g c w an on o e wv m a c -- ~¢un¢->-|-¢--|».--uceognfi . 2525a no iuflinm mu E .555 mu-c .:o$auu..E: 5:520 5. m. Q. Q. Q. QR. 5250.15 @035 055550 e035 5325 05552:. ©3255: 5:550 3.55950 105555 E5: 5:550 E5 5:550 522G .::s=8=_ 3.232: magnum 25m 00855 . . E55 :55 E vomit: $355 5 m~m5=88= -. 05 o5 nah-mu o5 1:: fiaflaucit: 5555 3 M5953: 5555 o5 25m 6535.6 53555.5 5 55.35.55 :5: 05:21.8 E335 a5 5:352:55 :5: E5 5.35595»... 5325 5 52:25 553.2525“ 5. 50am A v3.5. NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 11 inoculation changed 48 percent of the soils to a higher group and left 52 percent of the soils in the same group. Inoculation alone (Table I) increased nitrification in 40 to 50 percent of the various groups of surface soils and 4o to 85 percent of the groups of subsoils sufficiently to move them to higher groups. Inoculation was more effective with the subsoils than with the sur- face soils, probably because the subsoils had been less subjected to nitrification in their original situation. Calcium carbonate had more effect upon soils of low nitrifying power than those of high nitrifying power, and on surface soils than on subsoils. Calcium carbonate increased nitrification of all surface soils originally nitrifying less than 25 p.p.m., 92 percent of those nitrifying 26-99 p.p.m., 73 percent of those nitrifying 100-199 p.p.m., and 46 percent of those nitrifying 200-399 p.p.m. With the subsoils, the percentages increased were 64, 75, 14, and 10 re- spectively. The subsoils were more basic than the surface soils. Cal- cium carbonate decreased nitrification in a few of the soils originally i‘ with high nitrifying power. Inoculation and calcium carbonate combined increased nitrifica- tion in 92 to I00 percent in the various groups of surface and subsoils. More than 6o percent of the nitrogen of the ammonium sulphate was nitrified in 6o percent of the surface and subsoils ~ originally nitrifying 0-25 p.p.m.; approximately 80 percent of those in the group 26-99 and subsoils in groups 100-199; 100 percent in surface soils in groups 100-199; 93 percent in the surface and 84 A percent in the subsoils of group 200-299. A few of the soils still had a low nitrifying power after additions of calcium carbonate and inoculant. Applications of certain phos- phates increased nitrification in some of these soils (35). Relation of Nitrifying Capacity of Inoculated Soils to Amount of Nitrogen, v Basicity and pH of the Soils The presence of insuflicient numbers of nitrifying bacteria in the soil samples was partly due to natural factors such as the depth a from which the sample was taken, and partly to the extent of the suitability of the soil for nitrification of ammonium sulphate. In- oculation with inoculating liquid tends to eliminate natural de- ficiencies in numbers of bacteria. The results secured from inocu- Q lated soils were, therefore, used to ascertain the relation between the nitrifying capacities of the soils, and their pH values, the per- centages of nitrogen, and of basicity. - These data are presented in Table 2 in percentages of the num- bers of soils in each group. For example, in the group of inoculated N 0 I T A T S T N E M I R E m m w L U c I R G A M. X E T 3.. w» ,.0. N x” m 121 . ...»-¢. .-.-.- wqoeeoa + mmdxfl i l 1-190 omdam ?miwh m° - Q I w: =6 ........¢.mI w.N ..e.~|we. b:I:Iq~LnI .I.I.9¢$ 269.2. fiwwuwmam . . .+ www . .......ww.|wuw. .......Nw.|wwe. .......ue.|wme. .I..Im9|e Jnowwweo neuehwvw eew 8 S eew 8 3 C. E hm ew 2.. e e w. e e 3 e» Nu m w 5 m» nw mw. e e a e e e ea m w e w m» ea e w e e e e e e e e e E w. e e e e e e e e e ew w a w» e e e e e e m e e e 3 e .5 3 .3 S 3 ew x w I u e e e w w wu mu e an e» . .0 e e m e e u 2 e e» w w em 2. 3 2. w w 3.. mw e e e e w w em w.» 5 § e w w w x e e e e e e e 3 mu we 2. 3 w. mw e e e e e e e e e e w w 3 e w w. w Z a u w e e e e w 3. S. 2. e» 3 N» § we 3 E. mw 3 w w m w m e 3 e E a w B. em em w e m . e w e e e e . e m w m 3 2. x x x x x , x x . x x xx x x =emn:m web aemnum aek zemanw me? :ema=m web memnem nefi aemnem neh .E.ww..w 2:. .55..- e31 3 .E.e..w eenlweu ..E.e..w eenlwew .E.e.e e213 .E..w.e ma-.. =£§..a_.=z ====2E=z =3§2=....mz =£:aew._:z ===8wE=z , =zzaewiz .3353 wwem we mwenwwweZ éewtmewwfiee e25 wweee new 133 e5 we memawneeweww me xweemmewaxe weewEe-we 8 mwwem weewewseenw E eeewwewew Ew-waefiia we wwewwnewwwww: we wwefieweww d 059w. NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 13 soils which produced 0-25 p.pm., of nitrate nitrogen from the am- monium sulphate equal t0 500 p.p.m. of nitrogen, 45 percent of the top soils contained 0-.03 percent of nitrogen, 31 percent contained .03-.06 percent, I6 percent contained .06I-0.I2 percent, and 8 per- cent contained .I2I-.I8 percent nitrogen. Most of the soils which contained .03 percent nitrogen or less nitrified less than 25 p.p.m. of nitrogen. Nearly all the soils which contained over 0.12 percent nitrogen nitrified more than 200 p.p.m. Most of the soils with basicity 0.3 or less nitrified less than I00 p.p.m. Most of them with basicity more than 2 percent, nitrified ; over 200 p.p.m. Soils with pH less than 5.5 nitrified less than I00 ~- p.p.m. Practically all soilswhich nitrified over 300 p.p.m. of nitro- gen had pH values of 7.6 or over. Therefore, they were slightly alkaline. About one-half of the soils which nitrified over 300 p.p.m. and two-thirds of those nitrifying over 400 p.p.m. had basicities higher than the equivalent of 5 percent calcium carbonate. In general, soils with low nitrifying capacities had low nitrogen ritent, low basicity, and were slightly acid. Soils with high nitri- ying capacity contained more than 0.06 percent nitrogen, had asicities greater than 0.6 percent and pH values higher than 7.0. There were, however, some exceptions. l » i Witrifying Capacities of Texas Soil Types Nitrification capacities of a number of Texas soil types were studied by the method outlined above. Many tests were made before this method was fully developed in which the effect of calcium carbonate was ascertained. It was considered desirable to include the results of these tests also. Table 3 contains the nitrification capacities of a number of sur- face soils of Texas soil types. The soils are arranged in. the same geographical divisions as the soils whose analyses are presented in Texas Station Bulletin No. 549 Many of the figures in Table 3 are averages, but some are fof ionly one sample. When tests on ' different samples of the same type gave very different results, these differing tests are also included in Table 3. The upland surface soils of the Gulf Coast Prairie, the East Texas_Timber Country, the West Cross Timbers, and other non- calcareous soils have low nitrifying capacities for ammonium sul- phate. These are increased little by inoculation, but may be greatly increased by additions of calcium carbonate, or both inoculation and calcium carbonate. Soils of the Lake Charles, Amarillo, Bowie, Caddo, Kirvin, Norfolk, Lufkin and Susquehanna series are some which have low nitrifying capacities. 14 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION Table 3. Nitrification of Texas soil types (surface soils only). Nitric ‘ nitrogen in parts per million ' Calcium Soil Calcium carbonate alone Inoculated carbonate and inoculated p.p.m. p.p.m. p.p.m. p.p.m. Gulf Coast Prairie Upland soils Lake Charles clay loam . . . . . . . . . . . . . . . . 34 . . . . . . . . . . 397 . . . . . . . . . . Lake Charles fine sandy loam . . . . . . . . . . . 28 . . . . . . . . . . 396 . . . . . . . . . . Lake Charles clay . . . . . . . . . . . . . . . . . . . . . 4 . . . . . . . . . . 200 . . . . . . . . . . Edna fine sandy loam . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 350 . . . . . . . . . . Hockley fine sandy loam . . . . . . . . . . . . . . . 0 . . . . . . . . . . 160 . . . . . . . . . . Alluvial soils Miller fine sandy loam . . . . . . . . . . . . . . . . . 149 . . . . . . . . . . 306 . . . . . . . . . . Miller clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 . . . . . . . . . . 170 . . . . . . . . . . Ochlockonee silt loam . . . . . . . . . . . . . . . . . 28 . . . . . . . . . . 316 . _ , , _ _ , _ _ _ Ochlockonee fine sandy loam . . . . . . . . . . . 0 . . . . . . . . . . 120 . . . . . . . . . . Tri ity clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 _ . , , . , _ , . _ 322 _ _ _ , _ _ , _ _ _ main» clay - - - - - - - - . - - - - - - - - - - - - - - - -- 340 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. East Texas Timber Country Upland soils Bowie fine sandy loam . . . . . . . . . . . . . . . . . 0 0 193 316 Caddo fine sandy loam . . . . . . . . . . . . . . . . . 134 . . _ _ . , . _ _ _ 314 _ , _ _ _ _ , _ _ , Caddo fine sandy loam . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 208 . . . . . . . . . . Kirvin fine sandy loam . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 175 . _ . _ . _ , , _ _ Kirvin clay loam . . . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 36 . _ _ , . , , _ , , Nacogdoches fine sandy loam . . . . . . . . . . . 0 0 177 368 Orangeburg fine sandy loam . . . . . . . . . . . . 0 . . . . . . . . . . 200 . . . . . . . . . . Norfolk fine sand . . . . . . . . . . . . . . . . . . . . . . 0 0 217 218 Ruston fine sandy loam . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 59 . . . . . . . . . . Ruston fine sandy loam . . . . . . . . . . . . . . . . 0 0 33 162 Lufkin fine sandy loam . . . . . . . . . . . . . . . . . 113 217 175 395 Lufkin fine sandy loam . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 279 . . . . . . . . . . Susquehanna fine sandy loam . . . . . . . . . . . 0 0 172 282 Susquehanna fine sandy loam . . . . . . . . . . . 0 . . . . . . . . . . 196 . . . . . . . . . . Susquehanna stony loam . . . . . . . . . . . . . . . 0 . . . . . . . . . . 173 . . . . . . . . . . Susquehanna very fine sandy loam . . . . . . 0 . . . . . . . . . . 50 . . . . . . . . . . Tabor fine sandy loam . . . . . . . . . . . . . . . . . 0 67 321 360 Terrace soils Amite fine sandy loam . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 225 . . . . . . . . . . Cahaba fine sandy loam . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 132 . . . . . . . . . . Leaf fine sandy loam . . . . . . . . . . . . . . . . . . . 0 37 184 273 Leaf very fine sandy loam . . . . . . . . . . . . . . 16 59 360 330 lackland Prairies Calcareous upland soils Houston black clay . . . . . . . . . . . . . . . . . . . . 141 280 125 320 Houston black clay . . . . . . . . . . . . . . . . . . . . 243 521 202 509 Houston black clay . . . . . . . . . . . . . . . . . . . . 447 455 417 454 Houston clay . . . . . . . . . . . . . . . . . . . . . . . . . 288 420 160 397 Houston clay . . . . . . . . . . . . . . . . . . . . . . . . . 53 . . . . . . . . . . 430 . . . . . . . . . . Houston loam . . . . . . . . . . . . . . . . . . . . . . . . . 58 . . . . . . . . . . 308 . . . . . . . . . . Houston clay loam . . . . . . . . . . . . . .' . . . . . . . 0 . . . . . . . . . . 220 . . . . . . . . . . Sumter clay . . . . . . . . . . . . . . . . . . . . . . . . . . 289 465 231 403 Sumter clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 485 460 458 Bell clay (terrace) . . . . . . . . . . . . . . . . . . . . . 228 328 160 342 Bell clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 480 200 495 Lewisville clay . . . . . . . . . . . . . . . . . . . . . . . . 266 430 255 457 Calcareous stream bottom Catalpa clay . . . . . . . . . . . . . . . . . . . . . . . . . . 399 449 467 491 Non-calcareous upland soils Crockett fine sandy loam . . . . . . . . . . . . . . . 0 23 299 407 Crockett very fine sandy loam . . . . . . . . . . . 0 49 317 409 Crockett clay loam . . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 374 . . . . . . . . . . Wilson very fine sandy loam . . . . . . . . . . . . 20 50 406 470 Wilson fine sandy loam . . . . . . . . . . . . . . . . 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wilson clay loam . . . . . . . . . . . . . . . . . . . . . . 0 0 153 416 Wilson clay loam . . . . . . . . . . . . . . . . . . . . . . 60 80 402 447 Wilson clay loam . . . . . . . . . . . . . . . . . . . . . . 225 282 470 483 Wilson clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 440 209 481 Wilson clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 31 . . . . . . . . . . Irving clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 . . . . . . . . . . 199 . . . . . . . . . . Rolling Plains i, Upland soils Abilene clay loam . . . . . . . . . . . . . . . . . . . . . 245 404 420 503 Abilene fine sandy loam . . . . . . . . . . . . . . . . 6 18 283 361 Abilene very fine sandy loam . . . . . . . . . . . 200 228 485 502 Abilene very fine sandy loam . . . . . . . . . . . 434 486 452 478 Foard clay loam . . . . . . . . . . . . . . . . . . . . . . 58 . . . . . . . . . . 183 . . . . . . . . . . tl~t,.»..,i1s.-y_....n...z-.nmnfln S . YT WT , W¢7<~W-w NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 15 Table 3. Nitrification of Texas soil types (surface soils only). Nitric nitrogen in parts per million.—Continued Calcium Soil Calcium carbonate alone Inoculated carbonate and inoculated p,p.m. p.p.m. p.p.m. p.p.m. Bolling Plains——Continued Upland soils——Continued Miles fine sand . . . . . . . . . . . . . . . . . . . . . . . l0 Z28 6 232 Miles fine sandy loam . . . . . . . . . . . . . . . . . 41 78 328 356 Miles clay loam . . . . . . . . . . . . . . . . . . . . . . . 499 491 503 495 Vernon clay . . . . . . . . . . . . . . . . . . . . . . . . . . 291 486 232 483 Vernon fine sandy loam . . . . . . . . . . . . . . . . 395 388 384 430 Terrace soils Calumet very fine sandy loam . . . . . . . . . . . 65 . . . . . . . . . . 380 . . . . . . . . . . High Plains Upland soils Amarillo fine sandy loam . . . . . . . . . . . . . . . 0 0 244 285 Amarillo fine sand . . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 172 . . . . . . . . . . Amarillo silty clay loam . . . . . . . . . . . . . . . . 60 . . . . . . . . 467 . . . . . . . . . . Amarillo clay loam . . . . . . . . . . . . . . . . . . . . 10 . . . . . . . . . . 0 . . . . . . . . . . Richfield fine sandy loam . . . . . . . . . . . . . .. 210 . . . . . . . . . . 161 . . . . . . . . . . Alluvial soils Randall clay . . . . . . . . . . . . . . . . . . . . . . . . . . 120 201 452 402 Grand Prairie Upland prairie soils Crawford clay loam . . . . . . . . . . . . . . . . . . . . 92 . . . . . . . . . . 370 . . . . . . . . . . San Saba clay . . . . . . . . . . . . . . . . . . . . . . . . . 380 . . . . . . . . . . 309 . . . . . . . . . . West Coast Timbers Upland soils t B strop sand . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . 293 . . . . . . . . . . enton clay . . . . . . . . . . . . . . . . . . . . . . . . . . t/zgs 51o 48s 48s Milam fine sandy loam . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . 0 . . . . . . . . . . Windthorst fine sandy loam . . . . . . . . . . . . . 0 . . . . . . . . . . 324 . . . . . . . . . . Edwards Plateau Upland soils Reagan loam . . . . . . . . . . . . . . . . . . . . . . . . . 432 465 468 474 Reagan silty clay loam . . . . . . . . . . . . . . . . . 502 516 505 458 Reagan fine sandy loam . . . . . . . . . . . . . . . . 383 . . . . . . . . . . 393 . . . . . . . . . . Rio Grande Plain Upland soils Brennan fine sandy loam . . . . . . . . . . . . . . . 36 . . . . . . . . . . 390 . . . . . . . . . . Clareville fine sandy loam . . . . . . . . . . . . . . 355 512 424 456 Clarpville clay loam . . . . . . . . . . . . . . . . . . . . 453 445 446 458 Duval fine sandy loam . . . . . . . . . . . . . . . . . 0 27 265 355 Frio clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 . . . . . . . . . . 368 . . . . . . . . . . Frio silt loam . . . . . . . . . . . . . . . . . . . . . . . . . 435 460 482 464 Goliad fine sandy loam . . . . . . . . . . . . . . . . . 198 223 453 469 Hidalgo fine sandy clay loam. .' . . . . . . . . . 87 . . . . . . . . . . 110 . . . . . . . . Miguel fine sandy loam . . . . . . . . . . . . . . . . 326 365 435 447 Maverick fine sandy loam . . . . . . . . . . . . . . 384 370 315 381 Maverick clay loam . . . . . . . . . . . . . . . . . . . . 435 460 423 487 Maverick clay . . . . . . . . . . . . . . . . . . . . . . . . . 518 518 520 529 Crystal fine sandy loam . . . . . . . . . . . . . . . . 0 3 62 156 Crystal fine sand . . . . . . . . . . . . . . . . . . . . . . 30 72 264 207 Crystal loam, fine sand . . . . . . . . . . . . . . . . . 0 48 242 390 Montiola clay . . . . . . . . . . . . . . . . . . . . . . . . . 395 513 413 511 Nueces loamy fine sand . . . . . . . . . . . . . . . . 152 . . . . . . . . . . 353 . . - . . . . . . . . Orelia clay loam . . . . . . . . . . . . . . . . . . . . . . . 60 126 443 398 Orelia clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 420 482 507 Tiocana clay . . . . . . . . . . . . . . . . . . . . . . . . . . 289 . . . . . . . . . . 391 . . . . . . . . . . Uvalde clay . . . . . . . . . . . . . . . . . . . . . . . . . . . 499 480 498 493 Uvalde clay loam . . . . . . . . . . . . . . . . . . . . . . 455 492 477 499 Uvalde silty clay loam . . . . . . . . . . . . . . . . . 436 469 447 481 Uvalde silty clay . . . . . . . . . . . . . . . . . . . . . . 466 529 447 458 Victoria clay . . . . . . . . . . . . . . . . . . . . . . . . . . _ 61 50 318 368 Victoria fine sanfy loam . . . . . . . . . . . . . . . . 93 80 415 . . . . . . . . . . Webb fine sanlp loam . . . . . . . . . . . . . . . . . 38 200 343 410 film fine sandy loam . . . . . . . . . . . . . . . . . 431 468 435 438 illacy fine sandy loam . . . . . . . . . . . . . . . . 156 . . . . . . . . . . 410 . . . . . . . . . . Alluvial soils Laredo very fine sandy loam . . . . . . . . . . . . 479 519 473 481 74 . . . . . . . . . . 436 . . . . . . . . Rio Grande very fine sandy loam . . . . . . . . 16 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION Upland calcareous soils of the Blackland Prairies, the Rolling Plains, the Gulf Coast Plains and elsewhere have medium to high nitrifying capacities. When medium, nitrification is increased by inoculation but not by additions of calcium carbonate. This includes such soil series as Houston, Sumter, Abilene, Reagan, Clareville and Maverick. Alluvial soils, when non-calcareous, have low to medium nitrifying capacities; when calcareous, the nitrifying ca- pacity is usually medium to high. There are exceptions to the above general statements. The agronomic significance of differences in nitrifying capacities remains to be ascertained. Ammonia nitrogen was equally as valuable as nitrate nitrogen in pot experiments in a number of soils with low nitrifying capacity ( 31). Effect of Bacteria and Calcium Carbonate on Nitrification of the Soil Nitrogen The nitrification of the organic nitrogen already present in the soil was not necessarily comparatively low when the nitrification of ammonium sulphate was low. The soil nitrogen was nitrified to a fair extent in many soils in which ammonium sulphate was not nitrified at all or in which it even depressed nitrification. Additions of bacteria, calcium carbonate or both, increased nitrification of the soil nitrogen of some soils, but "did not have the same efiect with some other soils. When increases occurred, they were usually rela- tively small, not nearly so great as occurred in many soils for nitrification of ammonium sulphate. _ Data representing nitrification of soil nitrogen as compared with nitrogen of ammonium sulphate is given in Table 4 for a few of Table 4. Representative data on nitrification of soil nitrogen compared with nitrification of ammonium sulphate. Nitric nitrogen in parts per million ‘ Calcium Soil Calcium carbonate Type and source of nitrogen alone Inoculated carbonate and added inoculated Webb fine sandy loam, soil nitrogen . . . . . . . . . 53 51 42 53 Ammonium sulphate nitrogen . . . . . . . . . . . 2 72 138 327 Webb fine sandy loam, soil nitrogen . . . . . . . . . 84 82< 74 78 Ammonium sulphate nitrogen . . . . . . . . . . . 36 53 328 342 Maverick fine sandy loam, soil nitrogen . . . . . . 76 70 65 69 Ammonium sulphate nitrogen . . . . . . . . . . . 344 370 315 381 Randall clay subsoil, soil nitrogen . . . . . . . . . . . 64 70 71 94 Ammonium sulphate nitrogen . . . . . . . . . . . 68 160 372 419 Crystal fine sand, subsoil, soil nitrogen . . . . . . . 23 41 38 39 Ammonium sulphate nitrogen . . . . . . . . . . . 0 3 62 156 Crystal fine sandy loam, subsoil, soil nitrogen. 16 49 36 48 Ammonium sulphate nitrogen . . . . . . . . . . . 0 49 147 332 Orelia clay loam, subsoil, soil nitrogen . . . . . . . 37 64 54 80 Ammonium sulphate nitrogen . . . . . . . . . . . 0 156 319 420 Leaf very fine sandy loam, soil nitrogen . . . . . . 1 4 1 10 Ammonium sulphate nitrogen . . . . . . . . . . . 0 4 0 137 ._>;'.u..-.ri.n.i.ua.xm~n. ....,\.m - ' i!'”n.1§h'}‘5im “.11., >1» 4 1- NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 17 the many soils tested. With the first 3 soils, the additions had little efiYect on nitrification of the soil nitrogen, but had appreciable effects upon nitrification of the ammonium sulphate nitrogen. With the last 5 soils, the additions stimulated nitrification of the soil nitro- gen, but the increases in the nitrification of the ammonium sulphate were relatively much greater. Calcium carbonate increased the pro- duction of nitric nitrogen from soil nitrogen in some soils, but in many other soils it had no effect. Previous work has shown (20, 23) that, in general, the nitric nitrogen produced in nitrification tests from the nitrogen of the soil is related to the percentage of nitrogen naturally in the soil. It has also been shown that, on an average, the amount of nitrogen taken up by corn and sorghum in pot experiments is related to the amounts of nitric nitrogen produced from the soil nitrogen in nitri- fication experiments, the correlation coefficient with the first crop being + .708 @102 and with 4 crops, + .653 i .029 (23). Nitri- fication tests mad on samples taken from soils before and after cropping showed that the amounts of nitrates produced were reduced by cropping and related to the amounts of nitrogen withdrawn by the crops (23), the correlation coefficient being +. .680 i .029. Differences in the ability of soils of the same nitrogen content to furnish nitrogen to crops may be related, in part, to differences in the percentages of the soil nitrogen which can be converted into nitrates by nitrification. A summary of the percentages of soil nitrogen nitrified in I15 surface soils and I15 subsoils is given in Table 5. The nitric nitrogen produced in, 28 days in soils and sub- soils containing .03 percent or less of nitrogen, ranged from 7 to over 27 percent of the soil nitrogen. About 5o percent of all the v topsoils and 6o percent of all the subsoils nitrified 7 to I 3 percent 1 Table 5. Number of soils which nitrified the percentages of the soil nitro- ” gen in the groups given. Arranged according to percentages of soil nitrogen Percentages of nitrogen nitrified Nitrogen content 27% 0—6% 7—-l3% 14-20 21-27% or more No. No. No. No. No. 0—.03% nitrogen, top soil. . . . 0 2 4 4 3 subsoil. . . . . 0 4 3 1 1 ,.03l—.06% nitrogen, top soil. . l l0 l0 3 0 _; subsoil. . . . . 9 30 4 0 l .06l-. 12% nitrogen, top soil. . . . l4 29 7 1 0 - subsoil. . . . . 22 25 3 0 . 0 _ .l21—.l8% nitrogen, top soil. . . . 6 12 3 0 0 » subsoil. . . . . 3 5 l 1 0 t .1817‘, or more nitrogen, top soil. . 2 3 l 0 0 subsoil. . 0 2 0 0 0 I All soils. top soil (115) . . . . . . . . . . 23 56 25 8 3 i,» subsoil (115) . . . . . . . . . . . . 34 66 ll 2 2 18 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION ‘of the soil nitrogen. Nitrification of 7 t0 I3 percent of the soil nitrogen may be considered normal when the total soil nitrogen is ".06 percent or more. However, nitrification of I4 to 2o percent of the soil nitrogen might be considered as normal for surface soils containing less than .06 percent of soil nitrogen. About 2o percent of the surface soils and 30 percent of the subsoils nitrified less than 7 percent of the soil nitrogen, and about 2o percent of the surface soils and IO percent of the subsoils nitrified from I4 to 20 percent of the soil nitrogen. These latter 2 groups of soils could be con- sidered as poorer or better respectively, than the average in the extent to which the soil nitrogen is nitrified. A few of the soils nitrified more than 2o percent of the soil nitrogen, and in these soils the soil nitrogen could be considered as unusually easily nitrified. Other experiments, not here presented, showed that additions of calcium carbonate increased nitrification with 2o of 56 surface soils and subsoils lower than normal in nitrification, with I8 of 53 soils higher than normal, and with 30 of I23 soils normal in nitrification of the soil nitrogen. With the last 2 groups, the effect of the cal- cium carbonate, if any, was usually slight, and in some cases cal- cium carbonate decreased nitrification of the organic matter of the soil. Numbers of Organisms as Related to Nitrification Comparatively little work has been done on the relation of the number of organisms in the soil to nitrification. Wilson (77) esti- mated the number of nitrate bacteria in soils by a dilution method. Thorne and Brown (69), and Walker, Thorne and Brown (75) used the Wilson method with some modifications. In order to ascertain the changes in the numbers of nitrite and nitrate forming organisms during the period of incubation in nitri- fication studies, tests were made with surface soils of Houston black clay and Abilene fine sandy loam, both of ‘high nitrifying power. Five cultures of each soil were prepared and incubated, and one of each culture was examined at the end of 7, I4, 21, 28 and 45 days. Nitrates, nitrites and the numbers of nitrate and nitrite-forming organisms were estimated with the results given in Table 6. The numbers of nitrite-forming organisms increased from I0 to 20,000 per gram in 21 days and then decreased. The number of nitrate- forming organisms reached a maximum of 2,000 per gram at the end of 28 days. The maximum number of nitrite-forming organisms occurred at the end of the week in which the maximum oxidation _V occurred; that of the nitrate-forming organisms was at the end of the 7 days succeeding the maximum oxidation. In the first I4 days NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 19 1' Table 6. Elfect of days of incubation on the nitrification of ammonium * sulphate and on the number of nitrifying organisms Nitrogen found Amount Number of bacteria after incubation of nitrogen per gram of soil Incubation period of cultures ———-—i——————-———- per used as inoculants Nitric N Nitrous N period Nitrate Nitrite Days p.p.m. p.p.m. p.p.m. Number Number ' ~_ Houston black clay <1 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l0 150 i 7 . . . . . . . . . . . . . . . . . . . . . . . . . 64 42 106 0 l0 14 . . . . . . . . . . . . . . . . . . . . . . . . 275 12 181 40 750 21 . . . . . . . . . . . . . . . . . . . . . . . . 538 I 352 500 20,000 28 . . . . . . . . . . . . . . . . . . . . . . . . . 625 0 86 2,000 10,000 45 . . . . . . . . . . . . . . . . . . . . . . . . . 625 0 0 3,000 i Abilene flne sandy loam ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 750 7 . . . . . . . . . . . . . . . . . . . . . . . . . 84 66 150 50 2.000 l4 . . . . . . . . . . . . . . . . . . . . . . . . . 281 49 I80. 150 4,000 ‘ 21 . . . . . . . . . . . . . . . . . . . . . . . .. 538 3 241 1,030 20,000 28 . . . . . . . . . . . . . . . . . . . . . . . . . 588 2 - 49 2,000 15,000 45 . . . . . . . . . . . . . . . . . . . . . . . . . 650 1 61 250 10,000 i the production of nitrite was faster than the production of nitrate. The numbers of nitrite-forming organisms were usually much larger than those of the nitrate organisms. g In order to study further the relation between the numbers of organisms and nitrification, cultures containing ammonium sulphate 5 were made with 4 soils of high nitrifying capacities. At the end t_ of each week, for 5 weeks, determinations were made of nitric nitrogen, nitrous nitrogen, and the numbers of nitrate and nitrite- forming organisms per gram of soil. Duplicate portions of Ioo fgrams each of sterilized Houston black clay containing ammonium sulphate received at the end of each week inoculating liquid ‘equiva- §lent to 0.4 grams of each of the above cultures, were incubated 28 7days, and analyses then made. j, Table 7 shows that there was an increase of the nitrate produced leach week for the 3 5 days. The maximum production waslduring ‘the period 14-21 days for 3 of the soils, the period 28-35 days for the fourth. The numbers of organisms did not increase regularly igduring the period of experiment, and did not have a constant rela- tion to the production of nitrates. With the exception of the Clare- i ville fine sandy loam, the maximum number of organisms coincided with the end of the period of maximum production of nitrates. *- The production of nitrate nitrogen in the sterilized soil cultures ilwas related only slightly to the numbers of organisms with which they were inoculated. The maximum production of nitrates was ‘accomplished, apparently, by inoculation with I, 20o, 75o and 2,ooo L’ itrate-forming organisms per gram of inoculant. Inoculation with the maximum number of nitrate-forming organisms for each set roduced the maximum amount of nitrates. in 2 of the 4 sets. The 20 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION 25.3 QQQQN i: 3 3» A: ¢m~ 3 3 = Fl QNQv-IQO ¢NNOOQ v-u-i QM .-..-..-.. .-.--.....- .......-.-.....-. .-.. . -.-.-..-...-..v.... .. ¢ o .99:- an .931 mu .95:- a .231 z .922» b . . . .1: 0:: o_=>o..a-O . . .995 3 iii 3 .922» i.‘ 6.2% 1 6.2% n . . . . . . o =3 cesium .923 m» .923. w“ .222. T“ iii z dmaw n . . . . . .c >2» o_:>o.::O ..=»¢w mm Q .931 3 .925 3 6.2% S .926 n . . . . . . e =om GUST-HQ .5: Z 2E2 .54.. z mncufiZ 0255A 3955A 2:» ave-a 5525mm comma-oi uofizuuofi E uounuoha nomohmZ 53w 5.. aivuoan u: uni-EBA 150a!“ ma»? .2. ===~E~o .E.._.a Z mzcbmz uangng Z uiflZ Calm!“ e023!- coma-gal nuts-no »=:2=8=_ macs-noes“ Q8 UOOH 3.52:0 =90 uQ v2.5a nofleanufi mam wounioewh E cmncifia .3 nomaawmxc o5 E. wEmMGQMuO warmth-m: “a muonfiz: o5 uQ Quaam S o??? 21 I I O I I I I I O I I I I I I I I I a I I I I I I I I I I I I I I I O I I Q O I I I . . . . . . .. hwN =2 3 . . . . . . . . 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In another experiment to ascertain the effect of approximately v the same numbers of bacteria upon nitrification, samples of a cul- tivated soil were collected at several seasons of the year. The num- bers of nitrate bacteria in the samples were determined. Suspen- sions of Io grams of the samples in 50o cubic centimeters water were made, and 2o, 1o, 5, 2 and I c.c. were inoculated into 2 ster- ilized soils containing ammonium sulphate. After 28 days incu- bation, nitrates and nitrites were determined. The results in Table 8 show that 2 different soils inoculated by about the same number of organisms produce different amounts of nitrates, but not in direct proportion to the quantities of inoculant used. The total production of nitrates decreases, in each set of cultures, as a rule, with the decrease in the volume of inoculant, that is, with the decrease in number of organisms introduced. The quantity of nitrates produced is to a certain degree related to the i number of organisms introduced at different times, but the relation- ‘ ship is not high. The quantities of nitrates produced, per one c.c. of inoculant, usually increase as the volume of the same inoculant de- creases. That is to say, in each series, the production of nitrates is related to the quantity of inoculant but the relation is not high. Occurrence of Nitrites in Experimental Cultures The nitrites which are Ij9.< mm m mmm mm? mmv mm mmm m2 2m m2 mmm m2 Tm . .58. m2» 8.22m Smmm 2 2 mmm mm mmm N mmm m2 mmm mm mmm mm hi: . . . . . . . . . . . . . . . . . . . . . . .562 ma? 5.239 25mm L mvm m mmm mm mmv m 2m mm mmm vm mmm mm 2i. . . . .52: 5:» mtm mmmmm m n I Q I Q I I O Q Q Q Q O i O I I Q Q I Q Q Q I Q Q U“: mmm m2 mmm m2 mTum £0 0.32m 22m s m2 v mmm 2. mmm 2 mmm mm mmm mm mmm vm 2|... 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Efiwow ué nomwaufiuum: no Mflflflwflfi m6 fiohfl 5H 013M. 3-1 NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. .u~ 055a oom @052- 0...: .55. Q Q Q Q Q ..................... .........QQNNO—|hUuN3 N Q .-.-................. ..-.. .....-. ....%QmOHQQQ-QH—HB Q Q W Q Q ................. ..... ....... ...........QQMNQ—|hQaNR Q Q ...-.............. ..-.. ....... ....humONQHUhQu§.$ Q Q ..-............... .... .. .... .-.........QQMMQ—l.-Uaflg QQQ Q ............. .... .... . . ... ....>m=UNHQO hQeflk Q Q N Q Q ........ ....... ... ........... ..............QUNMO—|MQQQ>P Q Q -.-..-..-....... .- ......-... . ....>fifi@nvfiQfiU-nofifik QQ Q Q Q ..-..... .. -... - .......-.-.... ...-..-..-....QQ“m°Ql-—Qflfia Q ........ ...... ... . .. .. ....... . .-..%wmUHQNDhQ&Ui Q Qfifi Q Q Q ....... .. .. .... .... .......... .............QONMO—|hQaflB v2 w? 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When the soils were not puddled, nitrification was practically the same in soils con- taining 65, 75 or 85 percent of their water capacity. In another series of experiments, the effect of puddling upon nitrates was studied. The quantity of sodium nitrate containing 0.05 grams nitrogen (500 p.p.m.) was added to the cultures and incubated for 28 days. The average nitric nitrogen content of the unpuddled soils when the water content was 65 percent of the water capacity was 626 p.p.m.; with 75 percent, 626 p.p.m., and with 85 percent, 631 p.p.m. For the puddled soils, the averages were 609 for 65 percent, 534 for 75 percent and 461 for 85 percent. Pud- dling, therefore, decreased nitric nitrogen approximately 3 percent, I5 percent and 25 percent respectively. The effect of puddling upon sodium nitrite equal to 500 p.p.m. nitrogen is shown in Table I3. The nitrite was converted completely to nitrate in all the unpuddled soils, and almost completely in the puddled soils containing water equal to 65 percent of the water capacity. The conversion of nitrite to nitrate was not complete in 3 each of the I6 soils containing Water equal to 75 percent and 85 percent of the water capacity. In addition, the sum of the nitrous and nitric nitrogen was less than the amount originally present. There was a loss of nitrogen in practically all of the puddled soils. The loss averaged about 40 percent when 75 percent of the water capacity was present, and about 63 percent when the water content was 85 percent of the water capacity. The. effect of water-logging is shown in Table I4. Very little nitrification of ammonium sulphate occurred in the I6 water-logged soils, although there were slight amounts of nitrates and nitrites formed in 4 of the soils. When nitrates had been added, losses of nitrates occurred with the water-logged soils. The nitrites added were not completely oxidized in some of the soils. Nitrites persisted in only 2 of the water-logged soils, and then only in very small quantity. Appreciable proportions of the nitrite nitrogen was con- verted to nitrate in IO of the I6 water-logged soils, but there were high losses of nitrous and nitric nitrogen in all the “rater-logged soils. The experiment does not show whether the nitrogen so lost was converted to other forms, or entirely lost. Nitrification of Ammonium Salts of Organic Acids Nitrification tests have been used to compare the value of nitrogen in different organic fertilizers, but the results varied in different soils (I8, 78). Temple (68) reported that ammonium citrate, am- 4 ‘.lxl..AQJ s NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 33 monium oxalate and ammonium tartrate nitrified faster than am- monium sulphate or chloride, and Waksman (74) states that am- monium salts of organic acids are oxidized rapidly, but little data are available on the nitrification of ammonium salts of organic acids. Nitrification was conducted by the methods already described, with nitrogen added equal to 500 p.p.m. of the soil, in the form of ammonium sulphate, ammonium oxalate, ammonium acetate, am- monium tartrate and ammonium citrate. The nitrogen in the 4 organic ammonium salts were, in general, oxidized to a greater extent than that of the ammonium sulphate. The differences in the nitrification between the 4 organic salts were small. The average percentage of nitrogen oxidized in the 23 soils was 43 for ammonium sulphate, 59 for ammonium oxalate, 53 for ammonium acetate, 57 for tartrate and 56 for citrate. With Houston clay, Reinach silt loam and Nimrod fine sand, the nitrification of the organic com- pounds was less than that of the ammonium sulphate, being with the Houston clay subsoil, 32 percent for the ammonium sulphate, 29 percent for the ammonium oxalate, 0 percent for the ammonium acetate, 11 percent for the ammonium tartrateand 32 percent for the ammonium citrate. The nitrification of the organic salts in the other 2 soils were only slightly less than for the ammonium sulphate. The greater nitrification of the organic ammonium salts might be partly due to the lower degree of acidity of the organic acids than that of the sulphuric acid liberated in the process of nitrifica- tion of ammonium sulphate. In order to ascertain if such was the case, the effect of the addition of I gram (1 percent) of calcium carbonate to I2 cultures was tested. With all except 3 of the soils, when calcium carbonate was added, nitrification of the ammonium sulphate was practically the same as that of the ammonium oxalate or ammonium tartrate. With Miguel fine sandy-loam, Duval fine sandy loam and Nimrod fine sand, the nitrification of the organic compounds was less than that of the ammonium sulphate. The average nitrification without calcium carbonate was 4o percent for ammonium sulphate, 50 percent for ammonium oxalate and 40 per- cent for ammonium tartrate. With calcium carbonate, the average nitrification was 73 percent for ammonium sulphate, 66 percent for ammonium oxalate and 65 percent for ammonium tartrate. Carbonic acid is a very weak acid. The nitrification of ammonium carbonate, alone and with I percent calcium carbonate, was com- pared in 12 soils. The soils used were neutral or slightly acid but of low basicity, except one soil. All had low nitrification capacities. The nitrogen was added at the rate of 50o p.p.m. of soil, and the cultures were incubated 28 days. The average nitrification was: 34 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION soil alone, 40 p.p.m.; ammonium sulphate, I02 p.p.m.; ammonium carbonate, 18o p.p.m.; ammonium sulphate and calcium carbonate, 336 p.p.m., and ammonium carbonate and calcium carbonate, 32o p.p.m. Ammonium carbonate alone was nitrified to a greater extent than ammonium sulphate alone. When, however, calcium carbonate -was added, the nitrification in 1o of the I2 soils averaged almost the same for both salts. With Lake Charles fine sandy loam, the ammonium sulphate was nitrified appreciably less than the ammo- nium carbonate, but with Bowie fine sandy loam, the nitrification of the ammonium carbonate was appreciably less than that of the ammonium sulphate. On thewhole, the difference between the nitrification of the ammonium carbonate alone and the ammonium sulphate alone was apparently due to the greater amount of acid produced in nitrification of ammonium sulphate. Nitrification of Cottonseed Meal Cottonseed meal is representative of organic‘ compounds with which the nitrogen of the organic matter is believed to be first changed to ammonia before it is converted to nitrites and nitrates. Cottonseed meal has been reported to be nitrified to a greater extent than ammonium sulphate in some soils, but usually its nitrification is less. According to Temple (67), when tankage and other organic nitrogenous compounds are acted on by the soil organisms, ammonia is formed in excess of the acid products, neutralizes them, and allows the nitrification to proceed. The object of the work here reported is to ascertain why cottonseed meal is nitrified to a greater extent than ammonium sulphate in some soils, and the extent of nitrification of this substance in soils of different nitrifying powers. Nitrification of cottonseed meal has been studied, among others, by Lipman (43), Lipman and Burgess (44), Coleman (8), Allison (I), Carter (7) and Withers and Fraps (78). Three groups of 4 cultures each were prepared from each soil, namely,'one with no other addition, one with inoculating liquid, one with I gram calcium carbonate, and one with both inoculating liquid and calcium carbonate. Four similar cultures were prepared but with ammonium sulphate equivalent to 50o p.p.m. of nitrogen, and 4 similar ones with cottonseed meal containing an equal quan» tity of nitrogen. The amounts of nitric nitrogen found in the cul- tures which did not receive any nitrogen were subtracted from the amount in the corresponding cultures which received ammonium sulphate or cottonseed meal so as to ascertain the net quantities produced from these nitrogenous compounds. a i Nun M. m... 3v m» 0V..." MON h // 3w mm h» . 3w M“... 0 v w? w 3 m“ 5 2 s... E w“: ~m~ x: wmw v... ~ s. S. .5... Q“. MM. f. .5” 3, 5 m 2. 5N x S. MMM .5. S. v T S» E .5 .5 3.. S 3... . C N fl -.. -... A w...» 5 2. m... 3 3. S. F m w S. w m» ~ . m. NV mm m Q6 ... ... ... m... n 3. .5 m m... ~ . M 3w ww. 3. Wm. 3 5 3. 51...... m 3%. mm w» 3.. . wfi 5...? L .5 ww wl ww m~ .5. S. wvouflfi» s... m .5 2.. w“. m“ M... 3 S .. .. ..HV....H»...5.....¥...... < s $~ 3. aw. .5 f. w» h .......HH.....HH......................~w M w: Nmv ~w~ c . Na .......~w~..mw-.wa_vdwma%wz>w¢%wvfi w a. 5 5 s. ....... . M. .2»... ..........._.........._..... P S.» mav nwv c “w; o flaw 5.1.0.5.... 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E .5 5.3 .......=... 330 vwatsm .54.. m5 w: mm . vwak?» arm v.5... 55¢ 1.05.. . hm w“... ......................55.-.» < 0.3%.!» E55 100975.; vfidd m& 0v 05G uzflflflrzziuv 0 .E.~...:m 5...... w. .. . .......MJ..~ h; 05km»? 001M 0.5. < U0 7w0E ..E.fl ... ... . . .... Ed 87m 50 mg0wfl Efiwnuvvfik-dv QQGOSOU 0w§.w=¢.-QD .5 . ..... 0. .......A 0- 58-9 .0 .EE< 7.0%.... . .. .. my ouF-o.» find N WW5‘: 7000i Edd ...... ...... ...... 4 930C 0-%&_-D . . . . - . . -... - - . . . .. .. - . .%§@U m E4 MIOM 0vnflnnflé- AU ...hd UHOw-mg 9.: nau _..oz =@Q _¢-n—m@ho m 05W @‘}h“ 36 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION The results secured are given in Table 15. The soils are arranged l_ in groups according to the amount of nitric nitrogen produced from l?‘ the ammonium sulphate. Most of the surface soils used had high capacities to nitrify ammonium sulphate, while most of the subsoils have low nitrifying capacities. With the surface soils of high nitri- 3i fying capacity, the average production of nitric nitrogen in p.p.m. is 229 for cottonseed meal, compared with 462 for ammonium sul- phate. That is, the nitrification of the nitrogen of cottonseed meal in such soils was practically 50 percent of that of the ammonium sulphate. ' The additions of inoculating liquid or calcium carbonate stimu- lated nitrification of both cottonseed meal and ammonium sulphate in some of the soils and subsoils which otherwise nitrified below- the maximum. In most of the samples with low nitrifying capacity, especially the subsoils, calcium carbonate and inoculating liquid combined gave the greatest increases in nitrification. A few soils failed to nitrify high amounts of ammonium sulphate after receiv- ing both calcium carbonate and bacteria; this may be dueto need for phosphates (35), or to other factors not yet ascertained. The nitrification of cottonseed meal in soils of low nitrifying ~ capacity, though low, was greater than that of the ammonium sul- phate in 4 of the original soils and 3 of the original subsoils. When both calcium carbonate and bacteria were added, the ammonium sulphate was nitrified to a greater extent than cottonseed meal in all the soils. l With surface soils and subsoils of Pryor clay, of Uvalde silty clay, Pryor clay loam and Uvalde clay, the nitrification of cotton- seed meal was much below normal compared with ammonium sul- phate. This deficiency may have been due to insufficient conversion of organic nitrogen to ammonia during the experiment, but to ascertain the exact cause needs further investigation. Soils of low nitrifying capacity may convert greater percentages of the nitrogen of cottonseed meal to nitrates than that of ammonium sulphate. This may be due to the production of ammonia which reduces the acidity, as suggested by Temple (67). In soils of high nitrification capacity, ammonium sulphate is nitrified to a greater extent than cottonseed meal. Persistence of Elfects of Added Organic Matter on Oxidation of Nitrogen It is well known that microorganisms which increase during the rapid decomposition of organic materials will assimilate nitrates, l, already present in soils and will interfere with nitrification. After i F NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 37 the rapid decomposition which occurs when the organic matter is first added is finished, nitrates may again begin to be produced. Data as to the duration of the depressing effect of the organic matter in nitrification is inadequate, and some information on this point is herewith presented. The depressing effect on nitrification by glucose, sucrose and starch have been reported by Lipman at al. (45), that of sawdust‘ and other tree products by Gibbs and Werkman (38). Spaldin and Eisé£nfi¥igcéiX5111Mi.9?i.£h§lZ..Bil£ifi°§ll9BWVY§~iQ§PEE§§gdWWh. r111: carbon-niyggqmrativ.qf,lbe,nlarltlrié_flerials was greater than fT3o/fFrapisww(2I) reported that “organic mate-rwiaflasildiisapjwffgairmilrapidly difring the first 3 weeks after application, then much more slowly. The nitrification cultures were prepared by the method already described. Different amounts of representative organic substances were first mixed with soil, then with inoculating liquid, ammonium sulphate and with water equal to 5o percent of the water capacity of the soil. The cultures were incubated at 35°C for 28 days or longer, after which nitrates and nitrites were determined. The effect of certain organic additions on nitrification of the soil A nitrogen for 28 days is indicated by O and of ammonium sulphate is indicated by N in Table 16. The relative depressing effects were approximately in the order: cottonseed oil (greatest), then starch, cane suger, grapefruit peelings and pecan shells, least). The cocoa shells did not decrease nitrification of the soil nitrogen in any of the soils, and of ammonium sulphate in 3 of the 4 soils. The effects on nitrification of incubation for from 4 to 2o weeks are given in Table I7. Cocoa shells and pecan hulls had no de- pressing effect on nitrification. The depressing effect of grapefruit peelings lasted 8 weeks. With starch, cane sugar and cottonseed oil, the amounts of nitrates produced at the end of 2o weeks was _lower than those produced with the check culture, the decrease being greater with the 2 percent application than with the I percent. The effects of application of these substances persisted for a long time, although one would expect both the starch and sugar to be oxidized rapidly. Tests with 16 soils were made to ascertain the effects of ‘ the various organic additions upon sodium nitrate added equal to 50o p.p.m. of nitrogen. The average p.p.m. of nitric nitrogen in the 16 soils after incubating 28 days were: no addition, 7o; nitrate of soda, 643; nitrate of soda with I percent starch, 505; with 2 percent starch, 393; with I percent cane sugar, 480; with 2 percent cane sugar, 366; with I percent grapefruit peelings, 568; with 2 percent 38 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION .1035 055515 55.550555...’ .1035 .535: 2-2550... Q Q N M Q . . ......... ......... . . . . . . . . . . . .....=O§OWWQR a: mm 5mm w 2m 5 www 5 5mm c .. . . . . . . . . . . . ....._...=o:cmmo>> $5 -.-- ¢ . . . - . -. u o¢|-~ on .- c -.--- . . ..-|- - . - . .-.v..-.-.mmiiioua .. . .... .. . .... .. . . N . ..... .....................WN§=QQQumafcQn-flhw m3 mm =3. w» =2. 5 w? n n2. c . . . . ... .......... . . . . . . . . . . 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NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 39 grapefruit peeling, 503; with I c.c. cottonseed oil, 464; with 2 percent cottonseed oil, 339. All the organic additions decreased the nitric nitrogen content of the soil, the quantity of decrease differing with different soils,,and the decrease being greater with 2 percent organic material than with 1 percent. The average decrease was in the order: Wesson oil (greatest), then cane sugar, starch and grapefruit peel (least). Nitrification of Cyanamid Cyanamid is recognized as an excellent nitrogenous fertilizer. It is used alone and in mixed fertilizers. It is also used for the pur- pose of killing certain undesirable plants. Although under some circumstances it may prove injurious to plants, methods of applying it safely are well known. Previous investigations have shown that the nitrogen of cyanamid is not readily nitrified in some soils. Why this is the case, and how long cyanamid persists without nitrifica- tion, has not been clearly demonstrated. Cowie (Io) reports that cyanamid when applied alone changed to nitrate almost quantitatively in 8o days. De Grazia (I2) con- cluded that, until nitrification begins, cyanamid has a harmful effect on the microorganisms of the soil. Crowther and Richardson (11) found that the nitrification of calcium cyanamid is slow. Wagner, as quoted by Pranke (54), states that nitrification of calcium cyana- mid was normal with small applications, but with larger applications nitrification was low. Hall (39) reports that nitrification of calcium cyanamid did not occur in 2 soils. McGuinn (49), Cowie (Io) and Mukerji (50) concluded that dicyandiamid hinders nitrification, but does not hinder ammonification. Murata (51) found that am- monification of dicyandiamid was very slow. Kuhn and Drecksel (42) .state that calcium cyanamid increases the number of soil bacteria in neutral or alkaline soils, but has less effect on acid soils. The procedure used is similar to that described on a preceding page. The desired amount of cyanamid or other substance was added to 10o grams of soil together with inoculating liquid and water. After incubation, nitrate and nitrite nitrogen were deter- mined. v In preliminary work nitrification did not occur in 28 days when cyanamid equal to 50o p.p.m. of soil nitrogen was added. Soils of high nitrifying capacity were then tested, using cyanamid equiva- lent to 5o, I00, 25o and 50o p.p.m. of nitrogen. In some of the cultures ammonium sulphate providing 50o p.p.m. of nitrogen and sodium nitrite providing 50o parts p.p.m. of nitrogen were used in 40 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION addition to the cyanamid. With: cyanamid added equivalent to o, 50, I00, 250, 50o nitrogen in p.p.m. of the soil, the nitrate nitrogen found at the end of 28 days was 102, 101, 11o, 33 and 12 p.p.m. (averages of 9 soils). The nitric nitrogen produced when cyanamid was added averaged less than that in the soil alone, except when 10o p.p.m. was used. When the 9 soils received 50o p.p.m. nitrogen in ammonium sulphate in addition to cyanamid nitrogen, the nitrate nitrogen produced at the end of 28 days averaged 521, 407, I46, 3 3o and 15 p.p.m. with o, 5o, 10o, 25o and 50o p.p.m. of cyanamid nitrogen, respectively. The cyanamid was not nitrified, but de- creased the nitrification of the ammonium sulphate. It did not en- tirely stop nitrification until more than IOO p.p.m. cyanamid nitro- gen was added. When the soils received sodium nitrite equivalent to 50o p.p.m. of nitrogen in the soil, the average nitric nitrogen at the end of the incubation period was 447, 46o, 351, 98 and 37 p.p.m., corresponding to additions of o, 50, I00, 250 and 50o p.p.m. of cyanamid nitrogen. The cyanamid interfered with the oxidation of nitrite to nitrate, but did not entirely prevent it when less than 25o p.p.m. of cyanamid nitrogen was added. Previous work has shown that additions of calcium carbonate bring about nitrification in soils which would not otherwise nitrify. Tests were made to see if 1' percent of calcium carbonate affected the nitrification of cyanamid in soils which had low nitrifying powers for ammonium sulphate when calcium carbonate was not added. Some of the cultures were incubated for 28 days only. Others, after incubation for 28 days, were reinoculated by mixing each culture thoroughly with I0 c.c. of inoculating liquid and incu- bated for 28 days longer. The ammonium sulphate was nitrified very little in the soils when calcium carbonate was not added, but was nitrified to the average extent of about 75 percent when calcium carbonate was added. When cyanamid was added in addition to the ammonium sulphate at the rate of 5o, I00 or 25o parts per million, no nitrification occurred whether calcium carbonate was added or not, either in the first 28 days or when reinoculated and incubated 28 days longer. The calcium cyanamid decreased pro- duction of nitrates from the soil nitrogen. Calcium carbonate could not be expected to help the nitrification of cyanamid, since cyanamid itself may produce basic calcium salts. The results of the previous experiments indicated that cyanamid either destroyed the nitrifying organisms or temporarily hindered their activity. To secure information as to how long the injurious action persists, cultures from I2 soils with high nitrifying power for ammonium sulphate received cyanamid equivalent to 500 p.p.m. Jfinarmualukl’ ‘iupWWW “ ' " "if “ll-Qih NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 41 of nitrogen and were reinoculated with active nitrifying organisms after 0, 1, 2, 3, 4, 5, 6, 7 and 8 weeks of incubation. After the desired incubation period, each culture was mixed thoroughly with IO c.c. of inoculating liquid, returned to the beaker, and incubated for a further period of 28 days. The results with 12 soils show that the addition of cyanamid prevented nitrification although reinoculated with nitrifying or- ganisms after 8 weeks. With 2 soils, the experiment was conducted for periods up to 38 weeks with useof cyanamid equal to 50o, 25o and IOO p.p.m. of nitrogen in the soil. The results are given in Table 18. With 50o p.p.m. of cyanamid nitrogen, nitrification did not occur with Reagan silty clay loam after incubation for 38 weeks followed by reinocula- Table 18. Nitrification of different amounts of cyanamid after reinocula- tions. (Nitric N p.p.m.) Reinoculation after Addition 0 4 l6 24 30 38 weeks weeks weeks weeks weeks weeks p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. Reagan silty clay loam 4-7 No addition . . . . . . . . . . . . . . . . . . 94 208 313 438 494 525 500 p.p.m. cyanamid N . . . . . . . . 31 38 37 38 38 37 250 p.p.m. cyanamid N . . . . . . . . 31 38 41 44 51 272 100 p.p.m. cyanamid N . . . . . . . . 32 53 208 281 370 488 Uvalde silty clay 4-7 ' No addition . . . . . . . . . . . . . . . . . . 88 215 331 415 538 569 500 p.p.m. cyanamid N . . . . . . . . 8 44 56 76 88 245 250 p.p.m. cyanamid N . . . . . . . . 41 227 385 488 588 713 100 p.p.m. cyanamid N . . . . . . . . 125 250 385 460 556 663 tion, but some nitrification occurred in Uvalde silty clay when in- oculated after 3o weeks. With 25o p.p.m. of cyanamid nitrogen, nitrification occurred in Uvalde silty clay when inoculated after 4 weeks, and after 3o weeks with Reagan silty clay loam. With I00 p.p.m. of cyanamid nitrogen, nitrification began immediately with Uvalde silty clay, and after 4 weeks with Reagan silty clay loam. Cyanamid, or products of its decomposition, may interfere seri- ously with nitrification for long periods of time, and do not them- selves nitrify. This depressing effect may persist for 38 weeks or longer, and depends upon the amount of cyanamid added and the nature of the soil to which it is applied. Diffusion of the Toxic Substances of Cyanamid In the preceding experiments, the cyanamid was mixed thoroughly with the soil. In order to see if the toxic substances would diffuse, experiments were made in which the cyanamid was all placed in 42 BULLETIN NO. i693, TEXAS AGRICULTURAL EXPERIMENT STATION a hole punched in the center of each culture. The cultures were incubated for 2, 4 and 6 months. The cultures received inoculating liquid at the beginning of the experiment and had no further inoculation. Lumps of cyanamid, or its residue, were found in all the cultures at the end of each period. The results are given in Table 19. The amount of nitrate nitrogen in Reagan clay loam was less in the cultures to which cyanamid was added than in those of the soil alone, even after 6 months. The amounts of nitrate nitrogen in Table 19. Difiusion of toxic substances of cynamid in soil (Nitric N p.p.m.) Incubation Nitrification Nitrogen period (percent) added Treatment p.p.m. Months Months 2 4 6 _ 2 4 p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. Reagan silty clay loam, 7-24 No addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 200 313 . . . . . . . . . . . . . . . . . . Ammonium sulphate . . . . . . . . . . . 500 588 631 750 95 86 87 Cyanamid . . . . . . . . . . . . . . . . . . . . . 500 32 30 32 0 0 0 Cyanamid . . . . . . . . . . . . . . . . . . . . . 250 32 31 33 0 0 0 Cyanamid . . . . . . . . . . . . . . . . . . . . . 100 36 72 146 0 0 0 Uvalde silty clay, 4-7 No addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 253 347 . . . . . . . . . . . . . . . . . . Ammonium sulphate . . . . . . . . . . . 500 638 744 813 104 98 93 Cyanamid . . . . . . . . . . . . . . . . . . . . . 500 30 44 42 0 0 0 Cyanamid . . . . . . . . . . . . . . . . . . . . . 250 95 108 120 0 0 0 Cyanamid . . . . . . . . . . . . . . . . . . . . . 100 170 306 400 51 53 53 Uvalde silty clay which received 250 or 500 p.p.m. of cyanamid nitrogen, was less than that in the soil alone, even after 6 months, but there was some nitrification in the culture which received IOO p.p.m. of cyanamid nitrogen. The results show that the substances which interfere with nitrification diffuse to some extent from cyana- mid placed in one spot in the soil. According to McCool (47), soil conditions are usually favorable to the rapid transformation of cyanamid to urea. Free cyanamid may also be formed, which polymerizes to dicyandiamide. To ascer- tain which of some products from cyanamid are readily nitrifiable. or are toxic to the nitrifying organisms, dicyandiamide, guanidine carbonate, guanylurea sulphate and urea providing 50o, 25o and 10o p.p.m. nitrogen for each culture were tested in three soils. According to the results in Table 20, urea nitrifies readily. Guani- dine carbonate nitrified fairly well with Maverick loam and Uvalde silty clay loam, especially when added at the rate of IOO p.p.m. of nitrogen. The nitrification of guanidine carbonate was very low in Houston black clay. Guanylurea sulphate underwent only slight nitrification even when at the rate of IOO p.p.m. nitrogen. Dicy- andiamide showed no nitrification whatever, and interfered with NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 43 Table 20. Nitrification of cynamid products (Nitrate nitrogen in parts per million) Nitrogen Houston Uvalde Treatment added black Maverick silty p.p.m. clay loam clay loam None . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 100 74 Cyanamid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 6 l2 12 Cyanamid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 8 56 43 Cyanamid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7 176 140 Dicyandiamid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 6 13 l3 Dicyandiamid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 7 13 16 Dicyandiamid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 9 31 24 Guanidine carbonate . . . . . . . . . . . . . . . . . . . . . . 500 l4 244 120 Guanidine carbonate . . . . . . . . . . . _ . . . . . . . . . . 250 31 325 153 ' Guanidine carbonate . . . . . . . . . . . . . . . . . . . . . . 100 64 .. 210 153 Guanylurea sulphate . . . . . . . . . . . . . . . . . . . . . . 500 24 73 48 Guanylurea sulphate . . . . . . . . . . . . . . . . . . . . . . 250 36 113 64 Guanylurea sulphate . . . . . . . . . . . . . . . . . . . . . . 100 60 120 84 Urea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 588 638 625 Urea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 313 360 380 Urea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 168 215 185 nitrification of the nitrogen of the soil. It may be concluded that dicyandiamide and, to a lesser extent, guanylurea, hinder nitrifica- tion and would have this effect if they are formed from cyanamid applied t0 soils. The effect of dicyandiamide and guanylurea 0n the nitrification of ammonium sulphate was also tested in 8 soils. The dicyandiamid decreased nitrification of ammonium sulphate, even when quantities containing nitrogen equal to only IOO or 50 p.p.m. of soil was added. A similar experiment was made to test the effect of dicyandiamide upon the oxidation of nitrite to nitrate on 9 soils. The dicyandia- mide decreased the oxidation of nitrites, but not to such ‘a great extent as it did the nitrification of ammonia. In quantities equal to I00 or 50 p.p.m. of nitrogen, it had only a slight depressing effect. Guanylurea did not prevent nitrification of ammonium sulphate when an amount was used containing IOO p.p.m. of nitrogen, but was not itself nitrified even when only 50 p.p.m. was used. According to Fink (I6), adsorptive substances such as activated charcoal and iron hydroxide, have the tendency to eliminate the toxic affect of cyanamid on plants. Portions of cyanamid furnish- ing 500, 10o and 50 p.p.m. nitrogen were mixed with fuller’s earth, iron hydroxide, oat hulls, superphosphate, monopotassium and monocalcium phosphates, and elementary sulphur, and used in experiments similar to those already described. The additions did not decrease the depressing effect of cyanamid on nitrification. Because cyanamid is mixed with superphosphate in the manufac- ture of mixed fertilizers, nitrification experiments were made to test the effect of superphosphate. For mixtures A, B and C, 2 grams of superphosphate were mixed with the equivalent of I00, 44 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION 25o and 50o p.p.m. of nitrogen in IOO grams of soil in a porcelain dish, moistened with water and allowed to stand one Week. For 3 other cultures, the 2 grams of superphosphate were mixed with I00 grams of soil, the 3 quantities of cyanamid next mixed in, and cultures then prepared. Nitrification cultures were prepared as usual and incubated for 28 days. The experiment was repeated, with practically the same results. A little nitrification occurred with 3 of the 6 soils when the’ amount of cyanamid nitrogen was I00 p.p.m. Practically no nitrification occurred when the cyanamid nitrogen added was equal to 25o or 50o p.p.m. The results were practically the same whether the superphosphate was mixed sep- arately with the soil, or mixed first with the cyanamid, moistened and allowed to react for a week. That is to say, the wet superphos- phate did not react with the cyanamid to produce compounds more readily nitrified than cyanamid itself. The results offer an explanation why cyanamid occasionally does not give satisfactory crop yields. Cyanamid, on the one hand, is not readily nitrified and, on the other hand, it may hinder the activities of the nitrifying organisms. Consequently, if too much cyanamid is applied, nitrogen starvation of crops may follow. Suf- ficient time for the chemical decomposition of cyanamid before planting may avoid this difliculty. Small amounts of cyanamid may give more satisfactory crop yields than large amounts, because the small amounts nitrify sooner and, at the same time, do not depress so greatly the nitrification of the soil organic matter. J‘ Efiect of Sulphur on Nitrification Elemental sulphur is applied to certain soils to promote the growth of crops in Texas and other states on the Mexican border, and along the Pacific coast. In a few of the Western States, sulphur may act as a plant food on soils that contain sufiicient amounts of nitro- gen and phosphorus. Where nitrogen and phosphorus are deficient, and commercial fertilizers are applied, sufficient sulphur for plant food purposes are furnished by ammonium sulphate or superphos- phate (24). In Texas, especially in the Lower Rio Grande Valley, elemental sulphur is applied to calcareous soils on which certain plants, chiefly citrus trees, suffer from chlorosis. When placed in holes or furrows, the sulphur oxidizes to sulphuric acid which pro- duces acid spots or streaks from which the plant can secure iron, manganese or other elements otherwise not available to plants in some calcareous soils. Sulphur has been used experimentally where reasonable amounts would acidify soils of low basicity, in the study of cotton root rot (66), and in control of other plant diseases. _,,..i.4.... 1...- ._...._ e ”""YY“"","I¢IVWW*Yr~rv-—\'rr‘v-v “'*lYV"I-' . NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 45 Sulphur might interfere with nitrification by production of sul- phuric acid, 0r possibly in other ways. Lipman, ‘Prince and Blair (46), St. john (63), and Shedd (61) reported that sulphur had little unfavorable effect on nitrification, while Brown (5), and Ames and Richmond (2) reported depressing effects. Waksman (74) notes that certain sulphur-oxidizing bacteria may reduce nitrates to elemental nitrogen. Soils of high nitrifying capacity were selected. Portions of 10o grams of soil received additions of 0.5, 1.0, 1.5, 2.0 and 5.0 grams of finely ground sulphur, plus inoculating liquid and water. Some of the cultures received additions of 5 c.c. ammonium sulphate solution containing .05 grams of nitrogen, equivalent to 50o p.p.m. of the soil. Next, pH values were determined with the potenti- ometer using quinhydrone. In one experiment, sodium nitrate equal to 500 p.p.m. of nitrogen of the soil was added with sulphur to see if the elemental sulphur caused any loss of nitrates. All the additions of sulphur depressed nitrification of the soil nitrogen (Table 21) and of the ammonium sulphate (Table 22). The average nitric nitrogen produced from the soil nitrogen (11 soils) was 83 p.p.m. without sulphur, 31 with 0.5 percent sulphur, and 5 parts per million with 5 percent sulphur. The average nitric nitrogen production from soil plus ammonium sulphate was 553 p.p.m. without sulphur, 421 with 0.5 percent sulphur, 344 with 1 percent, 314 with 1.5 percent, 306 with 2i percent and 236 p.p.m. with 5 percent sulphur. As shown in Table 23, the oxidation of the sulphur during the incubation period of 28 days was not suflicient to bring the pH more than slightly below the neutral point of pH 7, even with 5 percent sulphur, except with samples 47662, 51293 and 51313 with which Table 21. Elfect of quantities of sulphur on nitrification of soil nitrogen. (Nitric nitrogen parts per million) Sulphur Number Type 0 .5% 1.0% 1.5% 2.0% 5.0% p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. 36482 Pawnee clay . . . . . . . . . . . . . . . . . . . . . . . . 63 40 14 4 2 0 39688 Pryor clay loam . . . . . . . . . . . . . . . . . . . . 50 4 1 0 0 0 44357 Reagan silty clay loam . . . . . . . . . . . . . . . 64 15 3 0 0 0 44369 Uvalde silty clay . . . . . . . . . . . . . . . . . . .. 60 4 9 2 3 5 49662 Houston black clay . . . . . . . . . . . . . . . . . . 61 17 8 5 4 3 50302 Catalpa clay . . . . . . . . . . . . . . . . . . . . . . . . 142 109 91 64 13 17 51293 Maverick clay loam . . . . . . . . . . . . . . . . 78 34 17 18 14 8 51298 Uvalde silty clay loam . . . . . . . . . . . . . . . 64 16 3 0 0 0 51302 Uvalde silty clay . . . . . . . . . . . . . . . . . . . . 120 28 12 0 2 0 51309 Frio silt loam . . . . . . . . . . . . . . . . . . . . . . . 90 14 3 0 0 0 51313 Maverick clay loam . . . . . . . . . . . . . . . . . 118 65 38 29 19 26 Average (11) . . . . . . . . . . . . . . . . 83 31 18 11 5 5 46 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION Table 22. Elfect of amount of sulphur on nitrification of ammonium sul- phate. (Nitric nitrogen parts per million) Sulphur Sulphur Sulphur Sulphur Sulphur Iiurnber 0 .59} l.0§§ 1.59% 2.09% 5.09% p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. 36482* . . . . . . . . . . . . . . 588 433 321 259 299 48 39688 . . . . . . . . . . . . . . . 513 430 350 331 350 330 44357 . . . . . . . . . . . . . . . 488 440 380 356 344 263 44369 . . . . . . . . . . . . . . . 575 395 384 252 326 245 49662 . . . . . . . . . . . . . . . 500 266 14 6 8 7 50302 . . . . . . . . . . . . . . . 619 547 516 491 457 451 51293 . . . . . . . . . . . . . . . 538 156 63 75 55 25 51298 . . . . . . . . . . . . . . . 538 475 463 438 390 363 51302 . . . . . . . . . . . . . . . 600 500 430 420 380 327 51309 . . . . . . . . . . . . . . . 538 430 387 325 269 175 51313 . . . . . . . . . . . . . . . 588 563 475 500 463 360 Average (11) . . . . . 553 421 344 314 306 236 *For name of soil type see Table 21. the pH values were 4.5, 5.0 and 5.2, respectively. The oxidation of nitrogen was lowest in soils 49662 and 51293, which were char- acterized by the lowest basicity (Table 23). Complete oxidization of the 0.5 percent sulphur would produce sulphuric acid sufficient to neutralize nearly 1.5 percent calcium carbonate, which was less than the basicity of any of the soils used. Part of the basicity (Table 23) is due to replacement of bases by hydrogen in the exchange complex. It, therefore, does not require neutralization of all the basicity shown in Table '23 to produce an acid soil condition. This is shown with samples 49662 and 51293 where the pH was reduced with 0.5 percent sulphur. The amounts of sulphur used in this study may appear excessive, since an addition of 0.5 percent is equal to 10,000 pounds on the basis of 2 million pounds of soil per acre. Sulphur is not soluble in water and cannot be distributed by soil moisture. It could not prac- tically be intimately mixed with the entire surface layer of 7 inches. Table 23. Elfect of amount of sulphur and nitrification of ammonium sulphate upon pH of soils Basicity Number of original Sulphur Sulphur Sulphur Sulphur Sulphur Sulphur soil, 0 0.5% 1.0% 1.5% 2.0% 5.0% CaCO % PH pH pH 11H pH DH 36482* . . . . . . . . . . . .. 4.8 7.7 7.6 7.7 7.4 7.3 7.0 39688 . . . . . . . . . . . . .. 6.4 7.5 7.3 7.2 7.0 6.5 6.8 44357 . . . . . . . . . . . . . .. 21.2 7.6 7.3 7.5 7.4 7.4 7.0 44369 . . . . . . . . . . . . . .. 13.6 7.4 7.5 7.6 7.5 7.2 7.5 49662 . . . . . . . . . . . . . .. 3.4 7.4 6.6 5.8 5.2 5.3 4.5 50302 . . . . . . . . . . . . . .. 21.7 7.9 7.2 7.3 7.1 7.3 7.1 51293 . . . . . . . . . . . . . .. 1.8 7.3 4.8 4.4 4.3 4.1 4.0 51298 . . . . . . . . . . . . .. 12.5 7.3 7.3 7.2 7.3 7.0 6.6 51302 . . . . . . . . . . . . . .. 17.9 7.4 7.4 7.5 7.5 7.5 7.1 51309 . . . . . . . . . . . . . .. 51.1 7.2 7.5 7.4 7.6 7.4 7.4 51313 . . . . . . . . . . . . . .. 5.2 7.5 7.3 6.9 5.8 5.4 5.2 *For name of soil types see Table 21. ,-,AL\,,’IIQ‘ NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 47 q Consequently, when small amounts of sulphur are applied in holes or furrows, the quantity in immediatecontact with the soil may p be as much as or more than the proportions used in this experimental ' work. Although sulphur particles may depress nitrification in the A soil near them, such depression in calcareous soils is limited in area and, therefore, must be regarded as not of practical signifi- cance. In soils of low basicity, a temporary or even prolonged de- pression of nitrification may occur when sulphur is intimately mixed in to produce an acid soil. it soil, nitrate of soda equivalent to 50o p.p.m. of nitrogen was added with sulphur to I6 soils and nitrates and nitrites determined after A 28 days incubation. The average p.p.m. of nitric nitrogen were, i with soil alone, 7o, sodium nitrate alone, 643, sodium nitrate with . I gram sulphur, 587, and sodium nitrate with 2 grams sulphur, A 564 p.p.m. Sulphur decreased slightly the amounts of nitrates » present. This depression may have been due partly to decrease in V nitrification of the soil nitrogen, or partly to reduction of the nig E trates by the sulphur or sulphur-oxidizing bacteria. Apparently any such reduction is comparatively small, less than IO percent. Etfect of Phosphorus, Magnesium and Iron on Nitrification Additions of calcium carbonate and inoculating liquid did not * produce maximum nitrification of ammonium sulphate with all the *6 soils tested. With some of these soils, additions of available phos- phates increased nitrification (35). Additional tests were made '_ with some other samples having low nitrifying capacities, and on A which the inoculation liquid, calcium carbonate and phosphates did not greatly increase nitrification. ; Of 6 surface soils, nitrification was increased in Miles fine sand and Elwood fine sandy loam by dicalcium phosphate, in Refugio loamy fine sand and Crystal loamy fine sand by dicalcium phos- iphate, magnesium sulphate and ferrous sulphate, and in Duval fine sandy loam by dicalcium phosphate and magnesium sulphate. These additions did not increase nitrification in Pryor clay. Dicalcium phosphate increased nitrification in samples of subsoils of Pryor i-clay, Webb fine sandy loam, Miles fine sand, Crystal fine sand, Maverick fine sandy loam, Crystal fine sandy loam, Crystal loamy ‘fine sand, Orelia fine sandy loam, Elwood fine sandy loam, Fannin §clay loam, Houston clay and Leaf fine sandy loam. Dicalcium phosphate and ferrous sulphate increased nitrification in subsoils of .,Miles fine sand. Magnesium sulphate increased nitrification in sub- foil of Refugio loamy fine sand, and dicalcium phosphate and fer- To ascertain whether sulphur decreases nitrates already in the. 48 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION rous sulphate increased nitrification in subsoils of Norfolk fine sand, Amarillo fine sand, Leaf sandy loam and Duval fine sandy loam. Dicalcium phosphate, ferrous sulphate and magnesium sulphate in- creased nitrification in subsoils of Victoria clay and Refugio loamy fine sand. Phosphorus in dicalcium phosphate increased nitrification in 4 surface and 19 subsoils, magnesium in magnesium sulphate in- 3 surface and 8 subsoils, and ferrous sulphate in 2 surface and 3 subsoils. These observations apply only to the samples studied and not to the type in general. Nitrification and Nitrifying Organisms in Two Field Soils During Various Seasons The greatest production of nitrates in field soils usually takes place during the warm seasons when temperature and moisture con- ditions are favorable for bacterial action. During the winter months, in countries in temperate climates, production of nitrates is likely to be small because the nitrifying organisms are inactive at low temperatures. Under Texas climatic conditions, however, where the tempera- tures are more or less moderate during the winter months, bacteria in the soil are likely to be active and thus to bring about production of nitrates. Nitrates may be moved toward the surface of the soil when evaporation is active, washed down when water penetrates, and be taken uptby plants and by soil organisms. The quantity of nitrates in a cultivated soil at any given time, therefore, depends on _ these several factors and not on any single one.) Jensen (41) in South Dakota found that the maximum amounts of nitrates in surface soils occurred in the early part of the spring; Russell (60) in England, early spring 0r early fall; Whiting and Schoonover (76) in Illinois, in the early spring or early summer; Gowda (37) in Iowa, during June and September; and Dorsey and Brown in Connecticut (15), during June and July in tilled plats, but not in pasture soils. Reynolds (58) in Texas, found the max- imum in July under cotton and in August under corn. Wilson (77) ifound the ammonia-oxidizing organisms ranged, in January, in an orchard grass plat from 4,000 to 12,000 per gram and in an orchard grass and alfalfa plat from 6,000 to 13,000. At pH 6.2 the num- bers were sometimes less than 1,000, and at pH 7.0 more than 35,000 per gram of soil. Walker et al. (75) found that the number of the nitrite-forming organisms ranged from 0 to 10,000,000 per gram, or more, according to the conditions. Thorne and Brown (69) found them to vary from 100 to 52,000 per gram, and that the maximum number was reached in the spring or early summer. ; A _.'.‘QnH/:Jeh.4uv- . NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 49 The numbers of bacteria, fungi, actinomyces and cellulose-decom- posing bacteria at different horizons of different genetic soil types were studied by Vandecaveye and Katynetson (73), and Timonin (70)- The work here reported‘ was conducted between March 1938 and December 1940. The soil samples were collected monthly, as nearly‘ as possible, from 2 cultivated plats at the Main Station Farm at College Station. No applications were made to one plat, while the other received annually 4,000 pounds of superphosphate and 12 tons of manure per acre beginning with I927. The crops grown were the same on both plats, and changed annually in rotation. The samples were collected in separate jars from IO different spots around each plot from the surface (0-4 inches) with sterilized spatulas. In the laboratory the jars were emptied into sterilized porcelain dishes and the soil was mixed thoroughly with sterilized spatulas. Five grams were used for the estimation of moisture, the quantity equivalent to Z10 grams of oven-dry soil for the determina- tion of nitrates, and the quantity equivalent to IO grams of oven- dry soil for the preparation of soil suspensions to be used for esti- mating the numbers of organisms. Table 24. Nitric nitrogen and moisture content of untreated and treated plots superphosphate No fertilizer and manure Nitric N Moisture Nitric N Moisture % % Date of collecting samples p.p.m. p.p.m. March 14, 1938-worn . . . . . . . . . . . . . . . . . . . .. 3. 10.46 8. 11 75 April 13, 1938 . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2. 8.12 9. l0 08 May l9, 1938 . . . . . . . . . . . . . . . . . . . . . . . . . . . . l. ll l0 l0 l2 36 June 20, 1938 . . . . . . . . . . . . . . . . . . . . ._ . . . . . . . 1. 96 6 00 July l4, 1938 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 45 12 24 August 8, 1938 . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 22 7 88 September 12. 1938 . . . . . . . . . . . . . . . . . . . . - . . . 34 3 86 October 13, 1938 . . . . . . . . . . . . . . . . . . . . . . . .. l 06 2. 94 November 14, 1938 . . . . . . . . . . . . . . . . . . . . . .. l 08 2. 64 December l5, 1938—oats . . . . . . . . . . . . . . . . .. 2 85 8. 66 January 16, 1939 . . . . . . . . . . . . . . . . . . . . . . . .. 96 1. 02 lIlI-l l-llli February l6, 1939 . . . . . . . . . . . . . . . . . . . . . . .. 96 18 March 20, 1939 . . . . . . . . . . . . . . . . . . . . . . . . . .. 72 l6 April 27, 1939 . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85 50 May 29, I939 . . . . . . . . . . . . . . . . . . . . . . . . . . .. l6 June 29, 1939 . . . . . . . . . . . . . . . . . . . . . . . . . . .. l0 50 July 31, 1939 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26 34 September 4, 1939 . . . . . . . . . . . . . . . . . . . . . . . . October 12, 1939 . . . . . . . . . . . . . . . . . . . . . . . .. November l3, 1939 . . . . . . . . . . . . . . . . . . . . . .. December l4, 1939 . . . . . . . . . . . . . . . . . . . . . .. January l8, 1940 . . . . . . . . . . . . . . . . . . . . . . . . . February 19, 1940 . . . . . . . . . . . . . . . . . . . . . . .. March 21, 1940 . . . . . . . . . . . . . . . . . . . . . . . . . . . NOON v-n-n ANMHH . _ ObwwUIUIUIUIQQQMQQBOIMQOQGOOMbOOEm-na-lmmv-a-lQr-IO n-u-n n ah N an n-u-n r-n MQQNMNNI-IQNGINQNQQQ QDNNQ: N N April 22, l940—cotton . . . . . . . . . . . . . . . . . . . .. 85 2 00 May 30, 1940 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 60 12.50 July 9, 1940 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 02 13.80 August 5, 1940 . . . . . . . . . . . . . . . . . . . . . . . . . .. 15 3.36 ‘i September 19, 1940 . . . . . . . . . . . . . . . . . . . . . .. 80 0.86 '- October 21, 1940 . . . . . . . . . . . . . . . . . . . . . . . . . 68 5.08 November 21, 1940 . . . . . . . . . . . . . . . . . . . . . . . December 23, 1940 . . . . . . . . . . . . . . . . . . . . . . . coco zencnwumnmmmwmwwmmMmommm~mmwq a w N N Nwwwuqnm u-mwhhflnnhfiQnfl $N . x w c .- u: . »'-.-.-.--..--..%%$§ ax w w a q . . ¢ . . - - - ¢-. --¢¢--»~.¢¢..-.wn@? n” O O Q Om Om Om 1 .. . ..... . ...............®MO# {ma BQQEQu-afiw W OW ON Own OOm OOH OOO.n COO-w ...........QMOM .Q aw5N5< O N N O O OM ... ...... .....................QMQM -bN Din-H 31:2 33:2 31:2 35:2 31:2 _ 33:2 31:2 7 022:2 moi-nun 953...; u: 3aQ 2E3: 3 9E3: N: _ 3:2: w =2... ooauim 2:3 ma i» fi .5: amuofivnn u: uonis2v 652% ucuuwua» 3a u13uan m-:E.:3.o:._:: 98 0393:: u... mhXEEZ 6w oEaa. .52 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION November ‘I940. There was no definite ratio between the numbers of the nitrate and nitrite-forming organisms. The ratio varies widely, but the tendency is for it to be close to I :1 when the organ- isms are inactive. The seasonal variations of the numbers of the autotrophic and the heterotrophic organisms were erratic. The bac- terial count is not believed to be accurate. In Table 26 are shown the numbers of the nitrifying organisms found at I, 6, 12, and I8 inches depth in the plot which received superphosphate and manure annually. As to be expected, the greater numbers of the organisms are near the surface soil and as a rule they diminish in number with the increase of the depth. There are a few cases in which the numbers were somewhat greater in the subsoil than in the surface soil, or between the different subsoil depths, but these are exceptions. Some variations in the numbers of all these groups of organisms occur at different depths, but it is not clear from the data whether they are due to season or some other factor. ‘ Summary Methods for conducting nitrification experiments, determining nitrifying capacity, and estimating numbers of nitrifying bacteria are outlined briefly. - Inoculation with nitrifying bacteria alone increased nitrification of ammonium sulphate slightly in about 50 percent of soils of orig- inally low nitrifying capacity. Calcium carbonate increased nitrifi- cation of ammonium sulphate in soils of low nitrifying power, and both calcium carbonate and bacteria increased nitrification of am- monium sulphate in over 9o percent of the soils and subsoils. Soils with low nitrifying capacity had low nitrogen content, low basicity, and were slightly acid or neutral.. ' s withphighgvnitri; fying capacities usually contained more than 0.06 percent nitrogen, "hadbasicities gireatermthan 0.6 percent and pH values were highfie-L 'tl1i§}fi\7.~ I ‘Upland surface soilswof‘ the Gulf Coast “Prairie, the East Texai ¢T 171155? Country,“ the West‘ Cross Timbers other non-calcalnfing soils have low“nitrifyinglcafpacitifeis.I The nitrifying capacities are increased little”ibyiwinoculation alone but are greatly increased by addition of calcium carbonate, or both calcium carbonate and bacteria. r Upland calcarmeoumsvsoils including thekwlilackland Prairies, the ,Rolling Piiifiéfktnd the Gulf Coast Plains have medium to high nitrifying capacities. When the nitrifying capacity is medium. nitrification is increased by inoculation, but is not usually increased i by additions of calcium carbonate. a i 4. 3 i.’ 1 i l. NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 53 The agronomic significance of ,the differences in nitrifying ca- pacities of various soils remains to be ascertained more fully. Am- monia nitrogen, in pot experiments, was equally as valuable as nitrate nitrogen in a number of soils with low nitrifying capacities. Natural organic nitrogen of soils and subsoils was nitrified from 7 to over 27 percent in 28 days. In about 50 percent of all surface soils and 6o percent of all subsoils, 7 to I3 percent of the soil nitro- gen was nitrified. Nitrification of 7 t0 I3 percent of the soil nitro- gen may be considered as normal for soils naturally containing 0.06 percent or more of nitrogen. _ Nitrification of 14 to 20 percent of the soil nitrogen may be considered as normal'for surface soils containing less than 0.03 percent of soil nitrogen. There are, of course, exceptions to these limits. Additions of calcium carbonate or bacteria, 0r both, increased nitrification of soil nitrogen in many soils, but did not increase such nitrification in all of them. The increases, if any, were usually rel ti y small. " A ing the 28-day incubation period of nitrifying cultures, the n mber of nitrate and nitrite-forming organisms increased to a max- imum and then decreased. The numbers of such organisms did not always increase regularly. When inoculated into sterilized soil, the production of nitrates was related to the numbers of organisms in- troduced only in a general way. When sterilized soils were inoculated with different quantities of cultivated soils, the nitrates and nitrites were related to the quan- tity of inoculant, but only in a general way. The quantities of ni- trates produced per unit of, inoculant generally increased as the quan- tity of inoculant decreased. Nitrites produced during nitrification are not always completely oxidized to nitrates. Appreciable quantities may remain in the cul- tures at the end of the incubation period. Insufficient numbers of or- ganisms which convert nitrites to nitrates at the beginning of the incubation may result in incomplete oxidation of nitrites. Additions of calcium carbonate may aid the persistence of nitrites, and addi- tion of magnesium carbonate may aid still more. Additions of small amounts of a nitrifying soil to a sterilized soil may result in persist- ence of nitrites, while inoculation with larger amounts of the same soil may result in complete oxidation of the nitrogen to nitrates. The conversion of nitrites to nitrates in a nitrifying soil is due al- most completely to biological processes, and only in very small amounts to chemical reactions. 54 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION ‘ Oxidation of nitrogen in soils is not appreciably due to sunlight. The water content of soils may range between 35 to I00 percent of the water capacity without appreciably affecting nitrification. On an average, I6 puddled soils containing water equal to 65 per- cent of the water capacity, nitrified the nitrogen of the soil 0r of ammonium sulphate only slightly less than corresponding unpud- dled soils. With water equal to 75 percent of the water capacity, puddled soils nitrified about 25 percent as much of the soil nitrogen as unpuddled soils, and 6o percent of that of ammonium sulphate. With 85 percent of the water capacity, I6 puddled soils averaged 6 percent of the nitrification of the soil nitrogen of unpuddled soils and 4o percent of the nitrification of ammonium sulphate. With 16 soils incubated 28 days, there was little average loss of - u - ‘WWW , added nitric nitrogen when the water content of the puddled SOllS was 65 percent, but the loss averaged 15 percent when the water content was 75 percent, and 27 percent when the water content was 85 percent of the water capacity. Sodium nitrite was converted to nitrate in both the unpuddled soils and the puddled soil with the water content 65 percent of the Water capacity. With water content 75 percent or 85 percent of the capacity, some nitrite remained in 3 of the 16 soils. There was an average deficiency of 4o percent of the total nitrate and nitrite ni- trogen with the water content 75 percent of capacity, and 63 per- cent deficient when water was 85 percent of capacity. s itrification did not occur to an appreciable extent in water-logged soils. Nitrate nitrogen added at the beginning of the incuba- gtion_was~fiartlgyg 16st; Added sodium nitrite disappeared completely‘ from I nearly all of the water-logged soils. Nitrite was converted partially to nitrates in many of the water-logged soils, but the sum of the nitrous and nitric nitrogen was less than the quantity orig- inally introduced. i In 23 soils differing widely in nitrifying capacity for ammonium sulphate, the nitrogen of ammonium sulphate was nitrified to the ex- tent of 43 percent in 23 days, compared with 59 percent of the ni- trogen in ammonium oxalate, 53 percent for ammonium acetate, 57 percent for ammonium tartrate and 56 percent ammonium citrate, respectively. When 1 percent calcium carbonate was added to 12 soils, the average nitrification of ammonium sulphate was greater than that of ammonium oxalate and ammonium tartrate. Ammonium carbonate was nitrified much more than ammonium sulphate in 12 soils, but when I percent calcium carbonate was added, the ammo- nium sulphate was nitrified only slightly less than ammonium car- m.-..t:;...LK>.rJILhAA-.Im‘ mewuauv-"”*"'"P""'““-’?'“”1"" l" NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 55 bonate. "The lower nitrification of ammonium sulphate as compared with ammonium salts of organic acids appears to be due chiefly to the high acidity of the sulphate ion released during the nitrification. In soils of high nitrifying capacity, the nitrogen of cottonseed meal is nitrified in 28 days to an average of 5o percent of that of ammonium sulphate. In soils or subsoils of low nitrifying capacity, the nitrification of cottonseed meal is likewise 10W, and, like ammo- nium sulphate, is improved by additions of calcium carbonate or in- oculating liquid, but in the- majority of cases, both additions are re- quired. Some soils and subsoils of low nitrifying capacity nitrified cottonseed meal more than ammonium sulphate, but when both cal- cium carbonate and inoculating liquid were added, the ammonium sulphate was nitrified to the greatest extent. With I soil and 4 sub- soils the nitrification of cottonseed meal was much below normal com- pared with that of ammonium sulphate, evidently due to conditions which interfered with the normal production of ammonia from the cottonseed meal. t fflwhen the fertilizing value of organic nitrogen in fertilizers is to be compared by means of nitrification tests, soils of high nitrifying capacity should be used. In soils of low nitri.fying capacity, the amounts of nitrates formed will depend upon the soil as well as upon the nature of the fertilizer. i i In incubation for 28 days at 35°, ammonium sulphate, with I or 2 percent cottonseed oil, produced the least nitrates, followed by starch, cane sugar, grapefruit peel, with pecan and cocoa shells having little effect on nitrification. After zgmpygeelgflsmfiincpubgamtuion, of the or anig rnatter, the depressing effects of the additions were in rder as given above, except that grapefruit peel and pecan shells had no depressing effect. In soils to which nitrates had been added, the quantity of nitrate nitrogen was decreased on incuba- tion on an average in the same order as given above. Cyanamid is not readily nitrifiable, and seriously depresses the nitrification of soil organic matter, sodium nitrite and ammonium sulphate when it is applied in the soil cultures at larger rates than 10o p.p.m. nitrogen. In soils which required additions of calcium carbonate for high nitrification, cyanamid depressed nitrification in the presence of calcium carbonate. The depressing effect of cyana- mid persisted for 6 to 1o months, even though the soil was inocu- lated with active organisms. The substances which interfere with nitrification diffuse from cyanamid placed in one spot in the cul- 1- ture. Of compounds derived from cyanamid, urea nitrifies readily, 56 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION guanindine carbonate was nitrified to some extent, guanylurea un-gé derwent slight nitrification, while dicyandiamide depressed nitri-‘ti . reported. fication of the soil nitrogen. I When applied at the rate of 0.5, I.O, 1.5, 2.0 and 5.0 percent, 1 ground sulphur interfered with the production of nitrates from the; nitrogen of the soil and from the nitrogen of ammonium sulphate. j This occurred even though the pH of the soil was over 7 at the of the incubation period. The depressing effect on nitrification in-_ creases with the percentage of sulphur added. Where sulphur is added in holes or furrows, as is done on some calcareous soils, i , will probably not affect production of nitrates to a detrimental ex-"I tent. A temporary or prolonged hindrance to nitrification may, .5 however, take place in soils of low basicity. Additions of sulphur" may also reduce the nitrate nitrogen in soils to which nitrates have been added, either by depression of nitrification of the soil, or by" reduction of nitrates, but the decrease was small in the work here _. In soils of low nitrifying capacity, in which the nitrification of ammonium sulphate was not complete after additions of inoculat- ‘i’: ing liquid and calcium carbonate, dicalcium phosphate increased a, nitrification in 4 surface and I9 subsoils, magnesium sulphate in 3 surface and 8 subsoils, and ferrous sulphate in 2 surface and 3 sub- soils. l/ln the 2 cultivated field soils, the maximum amount of nitric ni- trogen occurred in July, October and April, the minimum in Sep- tember, February, November and December. The maximum num- ber of nitrate forming bacteria were found in June, January and f, April. The number of nitrate and nitrite-forming bacteria at depths‘ of I, 6, 12, and I8 inches are given, and generally the numbers ~ diminish with depths. The bacterial count is not believed to be l‘: very accurate. Bibliography I. Allison, F. E. 1918. Some availability studies with ammonium phosphate and its chemical and biological effects upon the soil. Soil Science 5:1-80. 2. Ames, I. W. and Richmond, T. E. 1918. Sulfofication in relation to i nitrogen transformation. Soil Science 15:311-321. a 3. Beckwitli, C. S. 1921. The effect of fertilizer treatments on Savannah cranberry land. Soil Science 12:183-196. 4. Brown, M. H. I934. Some chemical and biological effects of cyanamid and certain other nitrogenous fertilizers, on various Iowa soils. Jour. Am. Soc. Agron. 26:442. 5. Brown, H. D. 1923. Sulfofication in pure and mixed cultures with special’ 5 reference to sulphate production, hydrogen-ion concentration and nitrifi- cation. jour. Am. Soc. Agron. 15:350-382. a say-Jr» T‘ IO. II. I2. 13. 14. 15. 16. 17. 18. 19. 20. 21. 2 F" 24. 25. 26. NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 57 Brown, P. E. and Burton, T. H. 1927. Microorganisms in some soil profiles in Iowa. Proc. First Int. Cong. Soil Science. 3:100-106. Carter, L. S. 1934. Some chemical and biological changes produced in a Fox sandy loam by certain soil management practices. Soil Sci. 40:223-236. Coleman, D. A. 1917. The influence of sodium nitrate upon nitrogen transformation in soils with special reference to its availability and that of other nitrogenous manures. Soil Science 4:345-432. Corbert, A. S. 1935. The formation of hyponitrous acid as an inter- mediate compound in the biological or photochemical oxidation of am- monia to nitrous acid. Biochemical jour. 2921086. Cowie, G. A. 1919. Decomposition of cyanamid and dicyandiamid in the soil. jour. Agr. Sci. 9:113-137. Crowther, E. M. and Richardson, H. L. 1932. Studies on calcium cyana- mid. I. The decomposition of calcium cyanamid in the soil and its effects on germination, nitrification and soil reaction. Iour. Agr. Sci. 22:300-334. De Grazia, S. 1908. On the nitrification of calcium cyanamid in various types of soil. Stay. Sper. Arg. Ital., 411241-257 (Exp. Sta. Rec. 20:72 5). Dhar, N. R., Bhattacharya, A. K. and Biswas, N. N. 1933. Photo- nitrification in soil. Soil Sci. 35:281. Dorsey, H. and Brown, B. A. 193 5. Seasonal variations in the reaction, nitrate and ammonia from differently fertilized permanent pastures. Connecticut Agr. Exp. Sta. Bul. 206. Dunlap, A. A. Fruiting and shedding of cotton in relation other factors. Tex. Agri. Exp. Sta. Bul. 577. Fink, D. S. 1934. Soil factors which prevent toxicity of calcium cyanam- id. jour. Am. Soc. Agron. 26:929-939. . F raps, G. S. 1903. Studies in nitrification. Amer. Chem. jour. 29:225- 241. Fraps, G. S. 1904. Nitrification and soil deficiencies. Proc. Assoc. Off. Agr. Chem. 179-183. F raps, G. S. I906. Nitrification and ammonification of some fertilizers. jour. Amer. Chem. Soc. 28:213-223. F raps, G. S. 1908. The production of active nitrogen in the soil. Tex. Agr. Exp. Sta. Bul. 106. F raps, G. S. 1915. Oxidation of organic compounds in the soil. Texas Agr. Exp. Sta. Bul. 181. Fraps, G. S. 1920. Nitrification in Texas soils. Texas Agr. Exp. Sta. Bul. 259. F raps, G. S. 1921. Relation of soil nitrogen, nitrification and ammonifi- cation to pot experiments. Texas Agr. Exp. Sta. Bul. 283. F raps, G. S. 1930. Possibilities of sulphur as a soil amendment. Texas Agr. Exp. Sta. Bul. 414. _ Fraps, G. S. and I. F. Fudge, 1932. Relation of buffer capacity for acids to basicity and exchangeable bases of the soil. Texas Agr. Exp. Sta. Bul. 442. F raps, G. S. and I. F. Fudge, 1937. Chemical composition of soils of Texas. Texas Agr. Exp. Sta. Bul. 549. Fraps, G. S. and Sterges, A. I. 1930. Occurrence of nitrites in soils. Tex. Agr. Exp. Sta. Bul. 412. - _ Fraps, G. S. and Sterges, A. ]. 1930. Nitrite production in soils. Ind. & Eng. Chem. 22:863. to light and 58 ~é9- 3.. 32. 33- 34- \35 3/6. fi 38 w‘ 40. 42. 43- 44- 1% 46. 47- 48. 49- BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION Fraps, G. S. and Sterges, A. j. 1931. Estimation of nitric and nitrous ; nitrogen in soils. Texas Agr. Exp. Sta. Bul. 439. F raps, G. S. and Sterges, A. j. 1932. Causes of low nitrification capacity if of certain soils. Soil Science 34:353-363. Fraps, G. S. and Sterges, A. j. 1933. The relation of the nitrifying i’ capacity of soils to the availability of ammonia and nitrates. Soil Science . : 36:465-470- Fraps, G. S. and Sterges, A. j. 1935. Effects of sunlight on the nitri- fication of ammonium salts in soils. Soil Science 39:85-94. Fraps, G. S. and Sterges, A. j. 1935. Availability of nitrous nitrogen. to plants. Texas Agr. Exp. Sta. Bul. 515. Fraps, G. S. and Sterges, A. j. 1937. Basicity of some phosphates as related to nitrification. jour. Amer. Soc. Agron. 29:613-621. Fraps, G. S. and Sterges, A. j. 1939. Effect of phosphates on nitrifying capacity of soils. Soil Science 47:115-121. Fraps, G. S. and Sterges, A. j. 1939. Possible losses of nitrogen from a acid soils through the decomposition of nitrites. Soil Science 48 :175-81. Gowda, R. N. 1924. Nitrates and nitrification in field soils. Soil Science 171333- _ I Gibbs, W. M. and Werkman, C. H. 1921. Effect of tree products on bacteriological activities in soil: I Ammonification and nitrification. Soil f. Science 1 3 :3o3-322. Hall, T. D. 1921. Nitrification in some South African soils. Soil Science 12:301-363. Haenseler, C. M. and Moyer, T. R. 1937. Effect of calcium cyanamid on the soil microflora with special reference to certain plant parasites. Soil Science 43:133-151. jensen, C. A. 1910. Seasonal nitrification as influenced by crops and till- age. U. S. Dept. Agr. Bureau Plant Industry Bul. 173. Kuhn, j. and Drecksel, O. I928. The influence of calcium cyanamid on the bacterial life in the soil. Z. Pflanzenernahr. Dungung Bodenk 7B, 105-18. Chem. Abstracts 22 :2o23. Lipman, C. B. 1917. Ammoniafiability versus nitrifiability as a test for the relative availability of nitrogenous fertilizers. Soil Science 3:63-75. Lipman, C. B. and Burgess, P. S. 1915. The determination of availability of nitrogenous fertilizers in various California soil types by their nitri- fiability. California Agr. Exp. Sta. Bul. 26o. Lipman, j. G., Blair, A. W., Owen, I. L. and McLean, H. C. I912. Experiments on ammonia formation in the presence of carbohydrates and of other non-nitrogenous organic matter. New jersey Agr. Exp. Sta. Bu1.p247. Lipman, j. G., Prince, A. L., and Blair, A. W. 1921. The influence of varying amounts of sulphur in the soil, on crop yields, hydrogen-ion concentration, lime requirements, and nitrate formation. Soil Science 12:197-207. McCool, M. M. 1933. Properties and use of calcium cyanamid. Boyce Thompson Institute of Plant Research. Professional paper VI, No. 24. McGeorge, W. T. and j. F. Breazeole. 1938. Soil structures: effect of puddled soils on plant growth. Arizona Agr. Exp. Sta. Tech. Bul. 72. McGuinn, A. F. 1924. The action of dicyanadiamid and guanylurea sulfate on plant growth. Soil Science 17:487-500. NITRIFICATION CAPACITIES OF TYPICAL SOIL AND FACTORS, ETC. 59 Mukerji, B. K. 1932. Studies on calcium cyanamid. II. Microbiological aspects of nitrification in soils under varied environmental conditions. jour. Agr. Sci. 22:335-347. Murata, H. 1939. Ammonification of dicyanadiamid and its derivatives in soil. Trans Third Comm. Intern. Soc. Soil Sci. A 137-9. Nelson, G. H., Levine, M., and Buchanan, I. H. 1932. Elimination of corrections for nitrites in nitrate determinations. Ind. Eng. Chem. Analyt- ical Edition 4:56. Panganiban, E. H. 1925. Temperature as a factor in nitrogen changes in the soil. jour. Amer. Soc. Agron. 17:1. Pranke, E. J‘. 1913. Cyanamid-manufacture, chemistry and uses. pp. 1-112. The Chemical Publishing Company, Easton, Pa. Puri, A. N.,‘Rai, B., and R. K. Kapur. 1946. Oxidation of nitrites and oxalates in soils. Soil Science 62:121-136. Rao, G. G. and Dhar, N. R. 1931. Photosensitized oxidation of ammonia and ammonium salts and the problem of nitrification in soils. Soil Science 311379- ’ * ‘ Rao, G. G. 1934. Newer aspects on nitrification: I. Soil Science 38:143. Reynolds, E. B. 1931. A chemical and microbiological study of Lufkin fine sandy loam in relation to productiveness. Texas Agr. Exp. Sta. Bul. 421. Richardson, H. L. 1932. Studies on calcium cyanamid. III. Storage and .mixing with superphosphate. jour. Agr. Sci. 22:348-357. Russell, E. I. 1914. The nature and amount of the fluctuations in nitrate content of arable soils. jour. Agr. Sci. 6:18. Shedd, O. M. 1919. Effect of oxidation of sulphur in soils on the solu- bility of rock phosphate and on nitrification. jour. Agr. Research 18: 329-345- Smock, R. M. 193 5. Some physiological studies with calcium cyanamid and certain of its decomposition products. Ohio Agr. Exp. Sta. Bul. 555- St. John, j. L. 1922. Sulphur as a plant food. Wash. Agr. Exp. Sta. Bul. 175, p. 15. p Sterges, A. j. 1942. Adaptability of silica gel as a culture medium. jour. Bact. 43:317-327. i Sokoloff, V. P. and L. I. Klotz. 1943. Decline and collapse of citrus trees in relation to nitrite in orchard soils. Calif. Citrograph 28 r290, 308. Chem. Abstracts 1943 37:6797. Taubenhaus, I. _T., Ezekiel, W. M. and Fudge, I. F. 1937. Relation of soil acidity to cotton root rot. Texas Agr. Exp. Sta. Bul. 545. Temple, I. C. 1914. Nitrification in acid or non-basic soils. Georgia Agr. Exp. Sta. Bul. 103. ~ Temple, j. C. 1912. Why do some soils nitrify organic nitrogenous sub- stances and the ammonium salts of organic acids faster than they do ammonium sulfate or ammonium chloride? Science 35:227-228. Thorne, D. W., and Brown, P. E. 1937. A comparison of the numbers of two species of Rhizobium and ammonia-oxidizing organisms in variously treated Iowa soils. jour. Am. Soc. Agron. 29:877. Timonin, M. S. 1935. The microorganisims in profiles of certain virgin soils in Manitoba. Canad. Jour. Rec. Sec. Bot. Sci. 13:32-46. Turtschin, Th. W. von. 1936. Zersetzung der nitrite in mit basen un- gesattingten boden und das problem der nitrifikation. Budenk. V. Pfian- zernahr 43:170-186. G 60 BULLETIN NO. 693, TEXAS AGRICULTURAL EXPERIMENT STATION Tandon, S. P. and Dhar, N. R. I934. Influence of temperature on bac- terial nitrification in tropical countries. Soil Science 38:183. Vandecaveye, S. C. and Katznelson, H. I940. Microbial activities in; soil VI Microbial numbers and nature of organic matter in various genetic soil types. Soil Science 50:295-311. Waksman, S. A. I932. Principles of Soil Microbiology. (second edition) The William & Wilkins Co., Baltimore, Md. Walker, R. H., Thorne, D. W., and Brown P. E. I937. The numbers of ammonia-oxidizing organisms in soils as influenced by soil management i practices. Jour. Am. Soc. Agron. 29:854." Whiting, A. L. and Schoonover, W. ~R. 1920. Nitrate production in field soils in Illinois. Ill. Agr. Exp. Sta.» Bul."225. Wilson, I. K. 1927. The number of ammonia-oxidizing organisms in Y soils. Proc. First Int. Cong. Soil Sci. 3:14. Withers, W. A. and Fraps, G. S. 1902. Nitrification of different soils. ; ‘ Iour. Am. Chem. Soc. 24:528-534. Whiting, A. L. I926. Some important factors controlling the rate of nitrification of organic materials. jour. Am. Soc. Agron. 18:854-876. snanva anaqwos 'n w ‘v I a v a a I 1 Wan-mama...“ a .