TEXAS AGEICULTURAL EXPERIMENT STATION. BULLETIN NO. 106 JULY,1908 The Production of Active Nitrogen in the Soil. By G. S. FRAPS, Ph. D., Chemist. f)‘ .\l\ ~\ ‘ __-_;:;I ___.———"‘ =__—, \ 33/ 1 t, \ ‘m fifil . ; d‘ in E ‘T‘\/';‘I"YIJ1="?"F ‘a J Post Office COLLEGE STATION, BRAZOS COUNTY, TEXAS. 7 TEXAS AGRICULTURAL EXPERIMENT STATIONS. OFFICERS. GOVERNING BOARD. (Board of Directors A. & M. College.) K. K. LEGETT, President . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “Abilene- T. D. ROWELL, Vice President . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Jefferson A. HAIDUSEK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .LaGra.nge J .M. GREEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Yoakum WALTON PETEET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Dallas R .T. MILNER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Austin L. L. McINNIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Bryan W. B. SEBASTIAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Breckenridge STATION OFFICERS. H. H. HARRINGTON . . . . . . . . ..LL. D., President of the College and Director J .W. CARSON . . . . . . . . . . . . ..Assistant to Director and State Feed Inspector W. C. WELBORN . . . . . . . . . . . . . . . . . . . . . . . . ..Vice Director and Agriculturist M. FRANCIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “Veterinarian E J. KYLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Horticulturist JOHN C. BURNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Animal Husbandry R .L. BENNETT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Cott0n Specialist O. M. BALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Botanist G. S. FRAPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Chemist C. E. SANBORN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Co-operative Entomologist N. C. HAMNER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Assistant Chemist E .C. CARLYLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “Assistant Chemist L. McLENNAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Deputy Feed Inspector A. T. POTTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Deputy Feed Inspector J. H. RODGERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Deputy Feed Inspector H. E. HANNA . . . . . . . . . . . . . . . . . . . .; . . . . . . . . . . . . . . ..Deputy Feed Inspector C. W. CRISLER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Chief Clerk W .L. BOYETT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Clerk Feed Control F. R. NAVAILLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Stenographer A. S. WARE . . . . . . . . . . . . . . . . . . . . . . . .l . . . . . . . . . . . . . . . . . . . . . Stenographer STATE SU B-STATIONS. W. S. HOTCHKISS, Superintendent . . . . . . . . . . . . . . . . ..Troupe, Smith County S. A. WASCHKA, Superintendent . . . . . . . . . . . . . . . . . . . ..Beeville, Bee County NOTE.—The main station is located on the grounds of the Agricultural and Mechanical College, in Brazos County. The postoffice address is College Station, Texas. Reports and bulletins are sent free upon application to the Director. TABLE OF CONTENTS. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 Methods of Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Effect of Nature of Soil on Production of Active Nitrogen . . . . . . . . . . . . . . . 6 Effect of Proportion of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8 Effect of Carbonate of Lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 D Relation of Acidity to Nitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 Relation of Bascicity to Nitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 Effect of Carbonate of Lime on Active Nitrogen . . . . . . . . . . . . . . . . . .. 12 Effect of Magnesium Carbonate upon Nitrification . . . . . . . . . . . . . . . . . . . . . . . 14 Nitrification Capacity of Acid Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14 Effect of Phosphoric Acid and Potash on Active Nitrogen . . . . . . . . . . . . . .. 15 Rate of Production of Active Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17 Production of Active Nitrogen from Fertilizer Materials . . . . . . . . . . . . . . . .. 17 Determination of the Availability of Nitrogenous Fertilizers . . . . . . . . . . . .. 19 Relation of Plant Growth to Production of Active Nitrogen . . . . . . . . . . . . .. 20 Estimation of Ammonia and Nitric Nitrogen in Soils . . . . . . . . . . . . . . . . . . .. 21 Relation of Production and Consumption of Active Nitrogen . . . . . . . . . . .. 22 Relation of Composition of Crop to Active Nitrogen of Soil . . . . . . . . . . . . .. 24 Relation of Active Nitrogen to Composition of Soil . . . . . . . . . . . . . . . . . . . .. 26 Relation of Active Nitrogen to Soil Deficiency . . . . . . . . . . . . . . . . . . . . . . . . . 28 Importance of Ammonia Nitrogen . . . . . . . . . . . . . . r . . . . . . . . . . . . . . . . . . . . . .. 23 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . .. 30 THE PRODUCTION OF ACTIVE NITROGEN IN THE SOIL. By G. S. Fraps, Ph. D. Nitrogen, one of the most important of plant foods, is largely stored in the soil combined with carbon, hydrogen, oxygen, and perhaps other ele- ments, in the form of organic compounds. This organic nitrogen cannot be taken up by the plant, but serves as a reserve store. By chemical changes in the soil, chiefly brought about through the agency of living organisms, the reserve is converted into compounds of nitrogen which can be taken up by the plant. We will apply the term active nitrogen to these nitrogenous compounds. Nitrogen can be taken up by plants in the form of nitrates, salts of ammonia, and certain organic compounds. The active nitrogen in the form of nitrates has received most attention from chemists. Nitrates are easily taken up by plants; they are also easily washed out of the soil. The ni- trates left in the soil in the fall, or formed during the winter, may be large- ly lost before spring by percolating water, if the land is not covered by a crop which takes them up. The conditions which influence the production of nitrates in the soil have received considerable study. Active nitrogen is also present in the soil in the form 0f ammonium salts. Ammonia is probably the chief form of active nitrogen in soils filled with water, such as rice soils, or swamps. Ammonia is fixed by the soil, and held in a much less soluble form than nitrates. It is therefore not so easily lost by washing as nitrates, and is perhaps not so readily taken up by plants. The ammonia in the soil is converted into nitrates by the nitri- fying organisms. Certain organic nitrogenous compounds may be taken up by‘ the plant, such as asparagin, glycocoll, and urea. These bodies are found in plants, or in animal excrements. It is possible that some nitrogen may be secured in these forms by plants grown in heavily manured fields. It is very doubtful if plants secure any nitrogen in these forms from ordinary arable soils. At the same time, such a possibility exists, and is a suitable subject for in- vestigation. For the sake of completeness we will mention the fact that leguminous plants, by the aid of the bacteria on their roots, can utilize the free nitro- gen of the air. The organic matter of the soil, or that introduced into it, is broken down by the action of organisms; the organic nitrogen being converted first into ammonia, then into nitrites, and finally into nitrates. The carbon is oxidized finally to carbon dioxide, the hydrogen to water. It appears probable that some of the organic nitrogen may be converted into nitrites or nitrates without passing through the intermediate stage of ammonia. (4) (See Report of North Carolina Experiment Station, 1901-2, Withers and Fraps.) The process which ends with the formation of nitrates is termed nitrification. The process which ends with the formation of ammonia is termed ammonification. Ammonification is an intermediate stage in nitri- fication and not a complete process in itself. It is possible to study the process of nitrification in the soil by an estimation of the nitrates produced, but estimation of the ammonia produced does not allow us to study the process of ammonification, since a portion of the ammonia has been con- verted into nitrates. Active Nitrogen.—We will apply the term active nitrogen to the nitrogen in the soil in the form of nitrates and ammonia, which nitrogen can be taken up by plants without further change. As we have already stated, some organic compounds may possibly afford nitrogen for plants, but we have at present no methods for the estimation of these bodies in the soil, in the minute quantity in which they may be present. The production of nitrates in the soil has received considerable study; the production of ni- trates and ammonia together have received comparatively little attention. It is one object of the present work to study the conditions which affect the formation of both ammonia and nitrates, that is, active nitrogen. METHODS OF WORK. The general methods of work adopted in these experiments are as fol- lows. Such modifications as were necessary for the different experiments will be mentioned in their proper place: Five hundred grams of air-dry soil, which had been shifted through a 3 mm sieve, was mixed with 20 grams of fresh garden earth, an amount of nitrogenous substance containing 0.3 grams nitrogen, and water equal to one-third of the saturation capacity of the soil. The nitrogenous substance and the garden earth were first mixed together, then these were incorporated with the dry soil, the water added and the whole mixed thoroughly until the mass was uniform. The mixture was then placed in 500 cc precipitating jars, shaking it down by tapping gently against a wooden block. A test tube, with a small perforation in the end, was inserted to a depth of about one inch, and the jar, with its contents, was weighed and placed in a water bath kept as near- ly as possible at 35 degrees C. The most satisfactory method" of marking the jar with its weight and number is by means of a pencil on a rough surface etched with diamond ink. Every Monday, Wednesday, and Friday each jar was placed on a coarse balance and water added slowly through the test tube until its original weight was restored. This method of supplying the water retains the surface of the soil in an open, porous condition. After four weeks the contents of the jar were mixed thoroughly. One hundred grams were placel in a funnel on a perforated porcelain disc, and washed with water until the volume of the filtrate was about 100 cc. Ni- trates were then determined in the filtrate by the Tiemann-Schulze method and calculated to the original, air-dry weight of the mixture. For the ammonia determination, an amount equal to 200 grams of the dry soil was placed in a flask with dilute hydrochloric acid (1 to 25) in quantity sufiicient to make 500 cc with the water already present in the sample. The mixture of soil and acid Was shaken thoroughly, filtered after standing over night, and 250 cc of the filtrate distilled with magnesia. The (5) ammonia was caught in standard acid and the solution titrated back with ammonia. Correction was made for the ammonia in the reagents. Both nitric and ammoniacal nitrogen were corrected from the quantity present in the original soil. " Practically all the tests reported in this paper were made cn duplicate jars of soil, but we give only the average figures in reporting the work. The saturation capacity of the soil was estimated as follows: Fifty grams soil are placed in a 1 1-4 inch carbon filter on a perforated porcelain plate, weighed and water added until the soil is saturated. After the soil has drained 15 minutes, protected from evaporation, the apparatus is weighed again. The gain inweight is the saturation capacity, and is expressed in percentage of the original soil. EFFECT OF NATURE OF SOIL ON PRODUCTION OF ACTIVE NETROGEN It has been proved (Fraps, Report North Carolina Experiment Station 1902-3; American Chemical Journal, March, 1903) that soils vary consider- ably in the readiness with which they serve as a medium forithe growth of the nitrifying organisms. Two soils provided with equal numbers of nitrifying organisms, and equal quantities of organic nitrogenous material, and placed under similar physical conditions, may produce very different amounts of nitrates in the same time. We apply the term nitrifying capacity to the ability of a soil to serve as a medium for the growth of the nitrifying organisms, compared with some other soil taken as a standard. It is essential that the two soils should be provided with nitrifiable matter, and placed under conditions favorable for nitrification, the conditions being exactly alike for each soil, and that each soil at the beginning of the experiment should contain the same number of nitrifying organisms of the same activity. The addition of nitrifiable matter is essential, since such material al- ready present in different soils may be quite different in its susceptibility to the attack of organisms. Measured in this way, Withers and Fraps (Report North Carolina Ex- periment Station 1902-3) found that soils showed a great difference in nitri- fying capacity, varying from 11 to 106 in the 15 typical North Carolina soils studied. The soils with the lowest nitrifying capacity were sands with low water capacity, low humus, low absorptive power for ammonia, and a moderate amount of humus, but a soil with low water capacity, low absorptive power, or low humus does not necessarily have a low nitifying capacity. We formerly used the term nitrifying power to contain the same mean- ing as our expression nitrifying capacity, but we have substituted the latter expression for the former, because several workers have used the term nitrifying power with an entirely different meaning from our usage. The term nitrifying power has been applied to the results of inoculating a cul- ture medium with the soil or with an extract of it, and incubating at a suitable temperature for the desired length of time. The quantity of nitrates produced in this method is, however, dependent upon the number and activ- ity of the organisms in the soil at the time of the inoculation, and therefore represents other conditions than the ability of the soil to support the organ- isms. The number and energy of the nitrifying organisms are influenced by (6) the temperature, water content of the soil, quantity of food present, physi- cal treatment of the soil, and other conditions as well as by the nature of the soil. The ammonia prcduced in the soil can, of course, only be studied profit- ably in connection with the nitrates. Since an unknown quantity of the simmcnia has been converted into nitrates,‘ it is not advisable to speak of the ammonifying capacity of a soil. Ammonifying power has been applied to the power of a soil to produce ammonia when inoculated into a suitable sterilized culture medium. Experimental Wcrk.——The object of the experimental work WZLS to as- certain whether soils vary as much in their capacity for producing active nitrogen, that is, ammonia and nitrates, as in their ability t0 produce ni- trates alone. The method of work was substantially as already described. Each jar of soil (500 grams) received 0.3 gram nitrogeniin the form of cotton- seed meal, water equal to one-third of the water capacity of the soil in question, and 2O grams fresh moist soil to provide the necessary organisms. The soils were kept at 35 degrees C. for fcur weeks, the lcss of water being rezstcred from time to time. At the end cf the period the nitrates and am- monia were estimated as already described. _ The results of the experiment are presented in the following table: TABLE L-Effect of Nature of Sail on Production of Activei Nitrogen. Percentage of Added PvTitrvgen Ranlchased on converted into ' Soil Nitrates Ammonia "Fora? Active Nitrates i Total Active No. (a) (h) Nitrogen (a) Nitrogen r l (zrHi) (a-Fb) 7 28.6 31.6 60.2 100 g 100 T7 12.1 44.5 56.6 42 94 T3 4.1 46.3 50.4 14 84 T5 1.9 44.5 46.4 7 T7 76 1.4 40.8 42.2 5 7U We find that while these soils varied widely, from 100 to 5, in nitrii fying capacity, the production of available nitrogen varies much less, from 100 to 70. These differences in the production of active nitrogen, though ' smaller, are in the same order as the nitrifying power of the soil. When the prolduction of nitrates alone is considered, the soils vary greatly, but if ni- trates and ammonia together are taken, the differences are much smaller. If nitrates are much more valuable to plants than ammonia, these differences are very important; but if there is little difference in the value of the two, soils do not vary greatly in their power to supply active nitrogen from the same organic bodies, but the difference is still sufficient to be of significance. (7) EFFECT OF PROPORTION or WATER on PRODUCTION or ACTIVE I, , , NITROGEN. The object of this work was to study the effect of the quantity of water present in the soil on the production both of nitrates, and of active ‘nitrogen. Two soils were used. The method of work was similar to that already described, cottonseed meal being used as a source of nitrogen. Wa- ‘ter was added in definite-percentages of the saturation capacity of the soils. Soil No. 76 is a light sandy soil from Nacogdoches, Texas. Soil ‘K0. 77 is the College soil, a brown loam. The results of the experiments are s13? follows: ‘III ‘Y jIABLE ll.—Effect of Proportion of Water on Production of Active Nitrogen. "IIJTFIQ"? n? '~ Percentage of Added Nitrogen Rank Based ~""'fi9‘5i7“7-3" converted into 1 on 24.112911 "rfsnuv _ i’ jNitrates 1 Ammonia Active i Nitrates Active addedpy, ; 1._.1_(a) t (b) Nitrogen (a) 1 Nitrogen Soil ‘ (a-i-b) 1 (a-i-b) 11.6.7.7. . -. I : 1 u ~4d Jill “V ._» ‘fig. V ; Y7 w‘ “- 22.2% 14.5 39.3 54.3 72 101 33.3%’ .1 __~ 2()_»5;if 33.3 ‘ 53.8 100 . 100 55.6% 15.4 41.6 ; 57.0 76 106 77.8% 0.4 38.3 I 37.9 0 i 70 1 $611 No. 76 § 1 22l217i> 5.0 i.‘ 30.9 35.9 l 135 104 33.21% 3.7 t; 30.9 1 34.6 j 100 1 100 55.6% 7.0 32.6 1 39.6 1 139 1 111 7718.% 0.6 § 24.7 '1 1~ 25.3 1 16 p 70 100% 0.7 1 21.0 1 21.7 y 1s 1 60 . ,8 if CO1’ r1131" .‘i[1ii\s.-' 5'11"!‘ i...T.1191111i91111_911911s9 31111111199 91111991119119 1s 11111911 199s 111 9911 N9» 19 ‘Ithaniijnpgspill l\‘fo.9.’?'l,'§.m(§eeHalsogable The greatest production of ni- 6iEadFF§é1§/“%’F%de§i§BtfiX3§i$qP§Fzazllizrr°iaiwhfi fgati? caPmti l‘? 5;: _N°- 1%“; P913995 .5193. r91 . 30% ‘é “a ‘on m S“ °- ‘S Ema 1i1111.99199s9 111 199191 9911 tent had a much less efiect upon both nitrification and production o! available nitrogen than the increase in water. ‘(s5 dflllf! 171i It appears that practically no nitrification takes place in soils saturated with water, and the plant must take up its nitrogen as ammonia or in organic bodies. EFFECT OF CARBONATE OF LIME. The fact is very well known that calcium carbonate accelerates nitrification. The object of our work was to ascertain if there was any re- lation between the acidity or basicity of the soil, and the effect of carbonate of lime upon nitrification within it, and also to study the effect of carbonate of lime upon the production of active nitrogen. The effect of calcium car- bonate was studied in thirteen soils. No increased production of nitrates oc- curred in two soils. In the others, placing the amount of nitrates formed in the soil without calcium carbonate at 100, with calcium carbonate the production of nitrates was graded from 125 to 340. These soils must be con- sidered as deficient in calcium carbonate so far as nitrification under the conditions of the experiment is concerned. Relation of Acidity to Nitrification-The acidity of a number of the soils was determined by the Hopkins method, namely, by shaking the soil with a solution of sodium chloride and titrating the filtrate with stan- dard sodium hydroxide. As pointed out by Veitch, this acidity depends upon the reaction between the soil and the sodium chloride by which iron and aluminum chlorides are formed, these compounds being acid to phenolphthalein. Only one of the soils was decidedly acid by this method. No rela- tion could be traced between the acidity of the soil and the effect of calcium carbonate upon the nitrification. (See Table III.) Although the soil with the greatest acidity was affected to the greatest extent by the calcium carbonate, nitrification was also increased decidedly by calcium carbonate in the soils low in acidity. While, therefore, it is probable that nitrification is always increased by calcium carbonate in acid soils, soils which are not acid may exhibit a decided increase in the same way. Relation of Basicity to Nitrificatiom-Since one function, at least, of the calcium carbonate is to neutralize the acids produced by nitrification, an attempt is made to trace some relation between the basicity of the soil and the effect of calcium carbonate. Basicity was determined by three methods: (1) Ten grams of soil were digested with 100 cc fifth normal nitric acid, for 12 hours and 10 cc. of the filtrate was titrated with caustic soda and phenolphthalein. Since salts of iron and aluminum are acid to this indicator and the corresponding hydroxides are precipitated during the ti- tration, this method does not include the basicity due to bases of iron and aluminum. The basicity measured is due to carbonates and easily de- composed silicates of lime, magnesia, and the alkalies. (2) Fifty grams of soil were digested with 100 cc. tenth normal nitric acid, for one-half hour, and 20 cc. of the filtrate titrated with caustic soda and methyl orange. (3) After the titration in (2) phenolphthalein was added and the titration continued until the solution became slightly colored. The difier- ence between methods (2) and (3) consists in the fact that (2) includes (9) basicity due to iron and aluminum in addition to lime, magnesia and alkalies, while (3) includes only lime, magnesia and alkalies. I The results of this work are presented in Table III. If the entire amount of nitrogen added to the soil were oxidized, 0.21 per cent of calcium carbonate would be required in the soil to neutralize the nitric acid so formed. No relation could be traced between basicity as measured by either of the three methods, and the effect of calcium carbonate upon nitrification. Other factors than basicity may enter into the effect of calcium carbonate. \10\ @@. . \ . . . . . . . . . . . . . . . . . .QMGN.~O .ZOw 00:1 0m. mw. wfiA mw wwm ocfi 555D mtofifim flow out xufin 223E no Al. mm. om. mfi aom i: .. . . . . . étmm 5E2 fivcww whznwwcmhmu mofi 2:. 2:. K. i 2: 2: . . . . . éoésafi éaw 502.2 m2 no. wfi. mm. a mew cofi . .. QHOWGQETQ ficwm ocm wkznwmcfific HQ 3. S. 23 i: Q: 2: zcezwwm .5 8E n: %.%. 5?. @m@. .....- .... . . . . - -..mcfifl@ »>.N~U C@M:S.W% 2» cm. R. w: 2: 2: ..:.e=oz< 2w .52 an V2252 m2 2.: 2:: i3 o omfi o2 .. . . . . ... . 1.15% “noxious: w»: aim mmfi mm. 3. Q. 2. 3: 2: ............_E§< 5:2 ma: 5&5 S: moA ofiA $04» i mo ooH . . . . .omco:c< cam .522 x032 c8253 Nmfi we. :. ow. 2 mm so: . . . . . . . émauowwcuwz flow 3E3 Ewfi ow EoUfiwm EQU 5m 36D 5m c0222 wumcombwmv ouwconbwU 4 ~: “£32 i @0522 w @9262 6Q mtmm EEQFU Cfiifiwmw 1 = @A.s,.%ofiw2 .23 ~23 3.522 258:2 QaNGOnTmO ESTJQQ mm 366mm |QOmv ~§Eu< coméomtxz 26.2.5“: .>:2£m .6 .9229... 3 ufifivm 2.. 2E4 .6 Emcofimo t. ..o»tml.._: m|_m<._. Effect of Carbonate of Lime Upon Active Nitrogem-Although the car- bonate of lime has a decided effect upon the production of nitrates in soils, when the ammonia is estimated the efiect of carbonate of lime upon the total quantity of active nitrogen produced is seen to be comparatively small. (See Table IV.) For example, the addition of carbonate of lime to soil number 141 increased the nitrification from 100 to 424, while the pro- duction of active nitrogen was changed only from 100 to 108. The carbonate of lime has practically no effect upon the production of available nitrogen in this soil. Considering all the soils, we find that while the effect of car- bonate of lime varies from 92 to 424 upon nitrification (placing the nitri- fication without it as 100) the total production of active nitrogen was from 74 to 116. Allowing for the error of analysis and the variations to be ex- pected when working with these productions of living organisms, we find that carbonate of lime has comparatively little effect upon the total pro- duction of active nitrogen. (12) 2: 2: Q8 v3 mN . . . . . . . . A3 c0333 oz El w: ma 3a gm W8 .. . . 2c: E oowconswO 2: 2: 3m w? Q3 .... . . . A8 mezzo?“ oz no ma 2m m6». m2 W3 . . . . o8: E oomconbwU 2: 2: Em wNm a.» .. . . . . . . . . . c2233“ oz m2 o: 2N gm 12 Q: . . . 6E: E ofioofitmO 9: 9: N3 i»: wm .. . . . . . . . . . cocmoww oz mmz ii 2N w? 9D oi . . . 6E: E ozéontmU 2: 2: m? 3m Hal . . . . . . . . . . . c2233 oz 3Q . . ~60 mNm odm . . . 6E: E otEonbwO 2: Q2 Eo 3% T8. . . . . . . A8 coEfiow oZ Q; Q: ofi mom $2 mNH .. . .08: E QHNGOATMO . 2: 2: w? 2a W3 . . . . . . . . . .. coEEow oz m: 3 8 w? 3W 3% 3.68: E wfiooobvO c3 Q2 WE Wfi 9mm .... . . E . . .. mezzo?» oZ m2 E N» i; wwm vd . . .105: E oowconowO 2: ¢2 W? gm 9m éocmoww oz em o: $2 we“ 3. W? .. . 5E: E Qzwcofitwu 2: 00H mi W: vdm .. . . . . . . . .. coumoww oz mm 2+: 3 2+: 3 3 28:2 5%.: z o>co< $52: z cmwobmz o>co< EcoEE< 322: z mom E Eosbwoorfi iottonwwz so 8E UQP5>GQU é woman “$8M 5M2: z wo3o< E owficoohom ‘ »ill,‘1\§§. » éomonfiZ o>_.u_.o< co 0E3 E utm-Bntmo E uootfl|h>_ UJDmrm <:.|m:2.00 0.. 0:000:01? >05 0:0 100mm: 0: 10.000020: 0.. >0£<0 2:00.000? $09220 203000 >0EE0: 00 00: 300030010 >05 W0:_0 00000 0: 250 000 .3 TE 8 :00 50 :00 5w 5H Em .5 20 00550: 000 000w 00: . . . . .. . . . . F003. O0:0m0 0052.. #19000. . .. . . W000 00:. @00:m0. #19000 . . . . . . . . . . W000 00:. r005: W00N010 000:3? . 233:0 00:0. 05.2500. @9000 . . . . F0200: £00: @010.A100000................. $00000: 20% 500:. w0: 09:00:00. ‘H9000. . . . 000.00.00.00 00:0? F05. 1010. @9000 . . . . . 050.0220 03 00:0. M56552. #19000. . . F0200: ::0 500:. >001? 1019000 . . . . . . . . . . . C05 00:07. 00:. 200905002000. A9000. . . . . . . . 5o mo 0w 00 fi 00 :0 50 5o $0 000 020% W030 00000 0: >83 250000 >0Q<0 250m0: 250m0: :5 5o :5 E 05 .5 00 00 00 5o 15 5m T5 :00 00 :5 00 00 5w 50w 00 2B 50 00 :2 :00 5w 00 80 500 :00 ~15 00 RATE OF PRODUCTION OF ACTIVE NITROGEN. The nitrogen recovered as ammonia and nitrates in our tests repre- sents the more readily available nitrogen, or that which is most easily at- tacked by bacteria. The transformation would continue at a decreasing rate until it would become so slow as to be practically indistinguishable from the change of soil nitrogen. We have determined the rate of production of nitrates and ammonia in one soil. A set of ten jars were prepared under the same conditions and kept in the constant temperature bath. Every week two jars were i removed for the determination of nitrates and ammonia. The quantity found was corrected from that originally present in the soil. The results are presented in Table VIII. TABLE VllL-Rate of Change for the Nitrogen of Cottonseed Meal. l Percentage of Nitrogen converted l during each period into Time in Days Nitrates Ammonia Total 7 —-0.4 +22.2 +21.8 15 +7.0 + 4.1 +11.6 21 +8.8 — 4.1 + 4.7 28 +78 — 5.7 + 2.1 35 +35 + 2-2 + 5.7 42 +0.8 — 0.9 — 0.1 49 +1.0 -- 4.8 — 3.8 56 +1.2 + 3.6 + 4.8 Total 29.7 16.6 46.3 Nitrification begins the second week, reaches its maximum during the third week and decreases to the sixth week, after which it increases slightly. The active nitrogen was produced in greatest quantity during the first week and the rate of production decreases to the fourth week, after which it is somewhat irregular. The formation of ammonia has its maximum during the first week and is positive during the second, after which it is for the most part negative owing to change into nitrates. At the end of the 56 days the nitrogen of the cottonseed meal was distributed as follows: In nitrates 29.7 per cent, in ammonia salts 16.6 per cent, in other forms 53.7 per cent. It will be noted that at the end of 56 days, under very favorable conditions for nitrification, a considerable proportion of the fertilizer nitrogen was still present in the form of am- monia. PRODUCTION OF ACTIVE NITROGEN FROM FERTILIZER MATERIALS. In 1901 Withers and Fraps [Journal of the American Chemical So- ciety 23, 318 (1901)] found that in a certain soil the amount of nitrates (17) produced from organic fertilizer materials was in the order of their avail- ability as measured by vegetation tests and solubility in potassium perman- ganate. A later study by the same authors (North Carolina Experiment Station Report for 1902-3) showed that this relation does not hold for all soils but that the rank of the fertilizers measured by the nitrates formed under similar conditions varies in difierent soils. Placing the nitrogen oxidized from cottonseed meal at 100, the rank of the other fertilizing ma- terials varied in 5 soils as follows: Ammonium sulphate 13 to 127, dried blood 7O to 120, fish 85 to 190, and bone 22 to 43. In_a further study of this subject the author has determined both the nitrates and the ammonia produced from different fertilizing materials. in other words, an estimation was made of the total active nitrogen pro- duced. Method of WOFk->—-FOI‘ the purpose of the work three soils were se- lected which differ considerably in nitrifying capacities. Soil 75 is a white sand from Nacogdoches, Texas, a poor soil, low in nitrifying capacity and with low water capacity. g Soil number 77 is a brown clay loam from College Station, Texas, of medium nitrifying power, good water capacity and responding well to applications of phosphor-ic acid. - Soil number 131 is a brown soil termed Orangeburg fine sandy loam, from Elmendorf, Texas. The nitrifying tests were carried out as already described. Each jar contained 0.3 gram of nitrogen in the fertilizing material to 500 grams soil. The tests were carried out in duplicate. Production of Nitrates.—The relative value of the different fertilizing materials on the basis of the nitrogen oxidized to nitrates is presented in Table IX. The results are similar to those in the paper by Withers and Fraps already referred to; namely, the rank of the fertilizer measured by the relative amounts of nitrates produced from it varies according to the nature of the soil. These variations are quite considerable. If only nitri- fication were considered, the nitrogen of bone and bat guano would have a higher value than that of cottonseed meal. These variations are appar- ently due in part to the fertilizing constituents carried by the material. TABLE |X.—Nitrification of Fertilizers.. i Percentage of Added i Nitrogen Oxidized to i i 4‘ Nitrates Rank lLIn soil iIn soilg In soil iIn soil In soil In soil x 75. J 77. 181; 75. 77. i 131. Cottonseed meali 8.2 20.81 76 100 1 10o i 10o Blood . . . . . . . ..1 6.6 128.1, 5.9 80 i, 114 ; 79 Bone ....... “i, 18.6 1 17.61 21.9 227 1 87 1 288 Bat guano-Hui 17.5 i 17.8 220 i 218 1 87 E 289 Cow manure-J; lost i 9.9i. 89 i lost I 49 y 117 i i Production of Active Nitrogen.—The nitrogen converted into ammonia and nitrates taken together, or the active nitrogen, as we term it, ex- pressed in terms of the total nitrogen applied is presented in Table X. The relative values of the fertilizers based on the quantity of active nitro- gen produced from them in four weeks under favorable conditions at the temperature of 35 degrees C. is also given in the table. TABLE X.-Nitrification and Ammonification. \ Percentage of Nitrogen . Rank converted into Nitrates and Ammonia p In soil 1n soil In soil In soil g 1n soil 1n soil’ 75. 77. 131. i 75. 77. 131. Cottonseed meal 151.5 39.4 49.3 100 1G0 ‘ 100 Blood - - - - - - - - 5.6.4 43.9 42.9 110 , 111 86 Bone . . . . . . .. 20.7 23.9 23.7 40 61 47 Bat guano- - - -- 29.1 24.8 33.5 "57 * 63 ' 67 Cow manure - -i . . . . 9,6 8,3 24, 17 Some variations in the relative value of the fertilizers are to be found, Blood, for example, varied from 86 to 111 in the three soils. These varia- tions are by no means as great as those of the nitrates taken alone. The relative amounts of active nitrogen produced from the different fertilizers depend most largely upon the nature of the material, and are in the order of the availability of the fertilizer. DETERMINATION OF AVAILABILITY OF NITROGENOUS FERTILIZERS. The amount of active nitrogen which can be produced from a given sub- stance in a reasonable period of time should be a measure of its availability. If the soil conditions are such that the maximum quantity of active nitrogen is not produced, or if the active nitrogen is produced but is Washed out, or otherwise lost, the fertilizing material is not at fault. Highly available organic materials are those which are converted ra- pidly into active nitrogen. Materials of low availability may produce an equal quantity of active nitrogen if given sufiicient time, but the change takes place so slowly in the soil that they have small effect. The question of time is a matter of importance in connection with the availability of fertilizers, and the results must depend, to some extent, upon the period of time during which the material is subjected to the influences of the soil and the action of the roots of plants. Quickly available materials, however, are generally considered as those which act efiectively upon the crop to which they are applied. The determination of the quantity of active nitrogen produced by the soil bacteria from different nitrogenous fertilizers under the same conditions may be used as a method for ascertaining the relative values of these materials. Some organic material must be taken as a standard. If it were desired to compare organic material directly with sodium nitrate by means of the quantity of ammonia and nitrates formed from it, it would be necessary to select such a period of time and such (19) conditions that the substance would be conver-ted into an equal amount of active nitrogen as would be formed during the growing season of the plant. It is, of course, very difficult to establish such conditions. According as a longer or shorter time is selected and the number and activity of the organisms used for inoculating the soil is greater or less, different results would be obtained. The comparison of organic materials directly with sodium nitrate is thus subject to serious difficulty. Comparison of difierent organic materials with some organic sub- stance taken as a standard does not ofier such difficulties, and it is believed that the method applied in this paper will be of value for some purposes. It cannot supplant vegetation tests or take the place of a rapid chemical method, but it should be of value in its own sphere. If the nitrifying test were continued for a long period, the more slowly available materials have a better opportunity to become oxidized and the difference between the slowly available and rapidly available nitrogen might not appear so large. There was some variation in the relative values of the nitrogenous fertilizers as measured by the production of nitrates and am- monia in the work just discussed. Large variations also occur in the determination of the value of different materials by means of vegetation tests in pots. The results of different individual experiments in vegetation tests vary considerably. For example, the value of the nitrogen of blood as compared with that of sodium nitrate at 100, has been estimated in several series of experiments by various workers as follows: 51, 58, 61, 68, 69, 73, 73, 76, 83, 85, 95. The average of several series of experi- ments agree better; thus Jenkins and Britton’s average for three years was 73, Wagner’s average is 69, Von Sigsmond’s 67, Pfeiffer, Franke et al, is 85. Availability will also depend to a certain extent upon whether one or several crops are used to extract the nitrogen. Quick acting fertilizers will appear comparatively more available with one crop than with sev- eral in which the slow have a greater chance to show results. RELATION OF PLANT GROWTH TO PRODUCTION OF ACTIVE NITROGEN. The object of this work was to ascertain the relation between the quantity of active nitrogen (nitrates and ammonia) produced in the soil and the quantity of nitrogen withdrawn by plants in pot experiments. It was planned that a portion of the soil (500 grams) should be placed aside in jars under the same conditions as other portions (500 grams) in vege- tation pots, in which corn was to be grown with phosphoric acid and potash but no nitrogen. At the end of the experiment, nitrates and am- monia were to be determined in the jars, and at the same time the corn was to be harvested, dried, and subjected to analysis. It was intended that similar conditions as regards production of active nitrogen should prevail in both series. As a fact, however, the conditions in the jars and the pots were not identical. The temperature in the plant house was higher than in the cupboard in which the jars were kept. The transpiration of the corn caused greater changes in the water content of the pots than oc- curred in the jars, and the periodic addition of water no doubt aided in the aeration of the soil. These differences tended to favor a greater nitrifi- cation in the pots containing the plants than in the jars. It would be (20) practically impossible to make the conditions identical. They are, however, to some extent comparable. In spite of the differences the results offer con- siderable of interest. Method of Work.—The following is a description of the experimental methods followedz-e-Five hundred grams of the soil were placed in a 500 cc precipitating jar and 100 cc of water poured on the surface of the soil. A test tube perforated at the bottom reached to the bottom of each jar. The soil was thus ventilated at the bottom, as in the pot experiments. The jars were kept in a dark cupboard at the room temperature and did not receive any further addition of water during the period of experiment. At the end of the time they were weighed, mixed thoroughly and portions taken for analysis according to the methods described below. The results of the analysis were calculated to the original weight of the soil. Vegetation experiments were made on the same soil in galvanized iron pots 8 inches in diameter and 8 inches deep with a 1-inch side tube (Wagner pot). The pot was ventilated from the bottom, a layer of gravel was first introduced and five thousand grams of soil were weighed into each pot. Each pot received 2.5 grams acid phosphate and one gram " potassium sulphate. The corn planted was grown for various periods in the different soils. The period of growth was the same, however, as the length of time during which the soil was allowed to nitrify in the jars. The effect on plant growth of other additions to the soil was studied at the same time. Most of the tests with nitrogen were made in duplicate. At the end of about nine weeks the corn was harvested, dried and subjected to analysis. The period of growth and of nitrification varied with different series of plants, and this fact must be considered in com- paring the different soils. DETERMINATION OF AMMONIA AND NITRATES IN SOILS. Reagents. Ammonia Free Water.--I. Acidify distilled water with sulphuric acid and distil in a room free from ammonia, rejecting the first 100 cc. Pre- serve in a glass-stoppered bottle. Ammonia Free Water.-—II. Add 10 cc sodium carbonate solution 5 per cent to 1000 cc water, evaporate off about 250 cc and cool. Pireserve in. glass-stoppered bottle. Standard Ammonium Chloride.—Dissolve 1.91 gm. ammonium chloride in 1 liter ammonia free water I. One cc equals 0.5 mg. nitrogen. Take 10 cc and dilute to 1000 with ammonia free water I or II. One cc equals .005 mg. nitrogen. Standard Colorimetric SoIution.——Use 10 cc weak ammonia chloride, about 80 cc ammonia free water, and 4 cc Nessler’s solution, diluting to 100 cc. 100 cc equals .05 mg. N. Analytical Process-Weigh out 40 gm. soil and treat with 100 cc. hydrochloric acid 1 per cent. Let stand over night, filter off 50 cc. (equal to 20 gm. soil), add 50 cc. ammonia free water, add 2 gm. magnesium oxide and distill off 50 cc. into a cylinder or flask. Make up to 100 cc. take 10 cc., dilute with ammonia free water, add 2 cc. Nessler’s solution and compare with standard. Then take a larger or smaller volume of the distillate, ac- (21) cording to the color in the preliminary test, make up at the same time as the standard, and compare in colorimeter. Make a blank determination, using 50 cc. acid, 50 cc. water and 2 gm. magnesium oxide. Distil off 50 cc., dilute to 100, and take 5O cc. for the Nessler determination. N itrates-Reagents. Standard Nitrate.—Dissolve 0.722 C. P. potassium nitrate in 1000 cc. water. Dilute 100 cc. of this to 1 liter, 1 cc. equals .01 mg. N. Phenol Disulphuric Acid.——Mix 15 gm. pure crystallized phenol With 100 cc. conc. sulphuric acid (1.84 sp. gr.) and heat six hours in boiling water. Preserve in a glass-stoppered bottle. Standard Colorimetric Solutiom-Evaporate 10 cc. of the standard ni- trate solution to dryness in a porcelain evaporating dish on a water bath. Add 1 cc. of the phenol disulphuric acid and stir thoroughly with a glass rod. After not less than ten minutes, dilute with water and make alkaline with ammonia. Then dilute to 100 cc. 100 cc. equals 0.1 mg. N. Analytical Process.—-Weigh out 40 gm. soil and treat with 100 cc. water containing 0.5 gm. alum. Filter, evaporate 25 cc. on water bath, and treat with phenol disulphuric acid, as directed above, in the preparation of the standard colorimetric solution. Compare with standard. RELATION OF ACTIVE NITROGEN FORMED IN JARS TO NITROGEN TAKEN UP BY THE PLANTS. All the data of this experiment are summarized in table XI. The work was carried out in duplicate, but only the average results are shown in the table. Columns 2 and 3 show the quantity of active nitrogen which would be formed in the pots, if the change took place at the same rate in the pots as in the jars. As we have said, the conditions were not exactly identical in the two series, so that it could not necessarily be expected that the changes would run parallel. The temperature in the pots was probably higher than in the jars, also additions of water were made frequently to the soil on account of withdrawal of water by the corn; this would probably lead to better aeration. These conditions would tend to a greater produc- tion of active nitrogen, and we find that it takes place. It is seen from the table that in most cases more nitrogen was taken from the soil by the corn than would be produced in 5000 grams soil in the jars. There are only two soils in which the nitrogen taken up by the plant was less. With several of the sols the consumption of nitrogen by the crop was considerably greater than that which would have been produced in the jars. Notably among these are the following: ' No. 831, Laredo silty clay, N0. 829, Houston loam, No. 822, Lufkin fine sandy loam, No. 851, Houston blacl: clay, No. 818, Wabash fine sandy loam. No. 845, Wabash silty loam. From the soils named above the plant removed from about 50 to 100 per cent more active nitrogen than would have been formed in an equal quantity of soil in the jars. (22) 1E ‘ i3 i. NS N8 _ i. N Q N? ME . w”: Nam 05m N E W w 5 H: i: WK __ ma m S 2m 3m _ I Q8 1a NS § N Q #2 m3 N411. _ i w 3 m...“ 1mm _ Qm NE 3: TN m 3 M2 N. m N3 _ ww gm l w z _ Wm QM m 3 #4.: mm w 5 3a w: + m... m2 3w mi 2 is m 2.. w m. _ mm “.2 w m 3 7 Z w an B”. N.» _ .2 93 N N um _ ._.._ v2 we w m I _ é Wm mwtfizz MEOEE< wEmhu mEF-w m< m< 532.2 cwuobmz M5283 205T: CQNOC-Z ho QEU QOuU cozzi 3n 2.5m .0 we 5cm E EEQB Bus? :> _> > .w~on_ E F50 xn a: co Q5 2am. a >5? 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Eot :cw ...>.E:oU comz>> 52o 3on3 c0520: I 5550 comtwnom .252 >33 mac 55:4 ............mnxw.r .OUQ._NA dcmm 3E ouwbfi cowtwnom .Emc_ >ucmw on: mccmzwsawsw ..........muXm1F.mv2UCO_v_.EQO_ 325m oc¢ E524 . . . . . . . . . . énxwh iwaooU .Euo_ covwnoI . . . . . . . . . . . . £33k :63“; 5E2 Em cuwtj .. . . . . .. . . . $53k .2323 in? >:._w onmpnq . . . . . . . . . Jfiszonvcowrinom ficmm out vzotoZ . . . . . . . . . . . QSCDOU COMZ>Q _UCfim QCC vZOF-OZ . . . ificzoU c0235 .Eno_ >923 mccmcwscmzm . . . ificsoUcowtmicm 65.1 wcfl mccmcoscwsw .. . . . (CCQOU c0255 62mm mew mccmcwscwsw \ \ \ V1 1\[‘ COW *0 wENZ torcgol comogtZ u>$o< m0 =¢:m_»m|._x u._m<._. hwnEcZ >uofi£onm4 It appears that with these soils the conditions for nitrification and pro- duction of ammonia are much more favorable in the pots than in the jars. Indeed the conditions appear to be more favorable in almost all the soils. The exceptions are soils numbers 834 and 820. Considering the table further, we find that all soils producing less than .05 grams active nitrogen per 5000 grams soil also yielded less than this quantity to corn, and were highly deficient in nitrogen (columns 5 and 6 of table). Above this point, the results are somewhat irregular, but are promising, and appear to indicate that a comparison of the active nitrogen produced in the soil under some standard conditions, to be determined, com- pared with a standard soil, may enable one to judge the immediate needs of the soil for nitrogenous plant food. The production of active nitrogen, and the quantity taken up by the corn, is considerable in some of these soils. One bushel of corn requires 1.5 pounds nitrogen in its production, for the entire plant. Assuming these soils were 7.5 inches deep and weighed two million pounds per acre, soil No. 820 containing at the end of the period sufficient nitrogen for 12 bushels corn and soil No. 830 sufficient for 124 bushels. Four of the soils con- tained sufficient active nitrogen for 66 bushels of corn per acre, or more. The consumption of the active nitrogen by the corn was still greater. Eight of the soils consumed enough, or more than enough, nitrogen for 66 bushels of corn, the maximum consumption being equivalent to 124 bushels per acre. It is evident that the draft of plants upon the soil in pot experiments is heavy, even though the plants do not reach maturity, as in these experi- ments. RELATION OF COMPOSITION OF CROP TO ACTIVE NITROGEN OF SOIL. Column 4 of table XI. shows the content of nitrogen in the dry matter of the corn, and column 7 shows the quantity of nitric and ammoniacal ni- trogen produced in the jars, expressed in parts per million. There is, in general, a relation between the percentage of nitrogen in the crop and the quantity of active nitrogen in the soil. The soil con- taining the largest quantity of active nitrogen, also yields a crop contain- ing the highest percentage of nitrogen in the dry matter (1.86 per cent). The crop containing the smallest percentage of nitrogen did not come from the soil yielding the smallest amount of active nitrogen, but the smallest percentage was found in a large crop from a soil of medium content of active nitrogen. No soil yielding less than 19 parts per million of nitrates or 26 parts of active nitrogen yields a crop containing over one per cent of nitrogen. With one exception, all soils yielding over 27 parts per million of active nitrogen contained more than one per cent of nitrogen. The exception is a soil which produced an unusually large yield of corn. There thus appears to be some relation between the active nitrogen in the soil and the com- position of corn. The composition and the yield of a crop appears to be influenced by other conditions in addition to the quantity of active nitrogen in a soil, (24) although a small quantity of active nitrogen cannot produce a large crop. The nature of the soil appears to exert considerable influence upon the size of the crop. It must be recalled that all these soils were provided with phosphoric acid and potash. _ Q These soils are highly deficient in nitrogen, and produce small quantities only of active nitrogen. (25) The cuts 0n this and the 1Jrece w>m._u o PE W W W K. m . W W mo N3. W a w , =:o%v coflfiwacm 23x uhspwufiahk WW wvwwww wads 2 I W m». W W H ..___..»;C:_~oU :cm...6nc.~_.WEmo_ Em swans? W mvw cvdm W m»; W 5. n1 W. WW» W E. W wfm W Jm~CmO~\CSCOQ/~ Hswwioz >2“. 35m; Fianna W m: mmdw mo N. W aw n»... 3.. W mo. m i; W . . . . ....>.t5o‘ . 1w 2 QEQE zwcwflwcc‘ zmnnm?» W m5 8 E W 3 2 W 3 W SW m .. W i. 3. 2 N w .. . . . . Bu. d. n/w z 2 EWWMQWWWW Wsv wéti. W m3 mvmem W 2W; W we. W i. c... 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W S. 1 . 1 W o =8cwrWf 1&2 Wesa 2E v=ot¢z i» W WW W W AO w m WW ~H ZESU coma; ncmm 9:» mccucoscwsm o?» |l‘1\l»l WW \ W‘ \ \ W W .\\\i 1\\\§ §l|.\l. l. ‘ l, ‘ i! \\\ \\l. \i.i‘l\fll‘ \lv[\iily“ \“ i1‘ 1.111 \ I, W W W W W \\\1 cw .5 WW cw» Z . W Z‘ W W watt: W nEoEE W U LL . L _ W t LE; EyU .5; Emu W. a EwU B; m< 7 w< < W =2 t. cotnuoq nun oEnZ W ioimwfimmmmqwi 85w. W W SE5W< W W W W wisrvlfiucnWucm so: WoW W ..mu_.._:Z cozzi En ELEcwE W wExQ WEimwcumfiW. W wEI W _7;:_.W,W_ 22c... mtwl E cwucpzz w>cu< W W W W W W W W 46w E =szwoqeoo 2 ramizz U>W3< t .B:m$mi.__x m._m<_. Beyond the first group of soils the results are irregular, though there is some correspondence between the total quantity of active nitrogen pres- ent, and the content of the soil in nitrogen. The average nitrogen in the six soils, beginning with No. 831, is 0.08 per cent, with an average produc- tion of 21 parts per million of active nitrogen. 1n the last six the average total nitrogen is 0.12 per cent and the production of active nitrogen 59 parts per million. The soil from which corn extracts the greatest quantity of nitrogen (No. 845) also contains the highest quantity of nitrogen, though it does not produce the largest amount of active nitrogen. The nitrogen present as active nitrogen was on an average 2.7 per cent of the total nitrogen in the first group of soils (five); 2.5 per cent in the second group (six), and almost 5 per cent in the last six. It is evident that the nitrogen was converted into active nitrogen at different rates in the three groups of soils. The figures, however, do not represent the production of active nitrogen,, but the quantity in the soil at the end of the experiment. RELATION OF ACTIVE NITROGEN TO SOIL DEFICIENCY. In column 6 of table XI. we have the crop produced with the aid of nitrate of soda for comparison with that secured with the soil nitrogen alone (column 5). Although the crops were grown for difierent periods of time, and the results can only be compared with caution, the results of a comparison are so interesting that it may well be made. An examination of this and other data in the table leads to the following results: All the soils (five) yielding less than 7 parts per million of nitric nitro- gen or 9 parts of active nitrogen are highly deficient in nitrogen. In no case is the crop larger than 8 grams, and the addition of nitrates to the soil increases the crop four-fold or more. Soils yielding '7 to 22 parts per million of nitric nitrogen or I9 to 27 parts of active nitrogen (six in number) appear to be deficient in nitrogen. Nitrates increase the crop 30 per cent or more. Two of the soils in this group appear to be exceptional, in that nitrification is more active in the jar than in the pot. We are at present unable to assign a cause for this difference. These soils appear to contain a fair amount of total nitrogen, and it is possible that the production of active nitrogen did not go on well in the jars. Of the nine soils yielding 22 or more parts per million of nitric nitro- gen, or 27 or more parts active nitrogen, four appear to supply a sufficient quantity of nitrogen, two respond slightly to nitrates, while three respond. considerably. On one of the soils nitrates appear to decrease the yield; in this soil only one plant lived, and did poorly in the pot which received nitrates. This soil is from an arid section, and may contain so much soluble salts that the additional quantity of soluble fertilizing materials added to it had an unfavorable effect. IMPORTANCE OF AMMONIA NITROGEN IN THE SOIL. The experiments here described have shown that at the end of four or even eight weeks a large portion of the active nitrogen produced from organic nitrogen fertilizers is present as ammonia, even though the condi- (28) tions were very favorable for their conversion into nitrates. It appears that ammonia must play a not insignificant part in plant nutrition, when fertilizer or manure is applied. It may be objected to these experiments that the ratio of soil to fertilizer is not in proportion to the quantity of nitro- gen applied per acre in practical agriculture. When fertilizers are applied to the soil they are, however, in much less finer condition than the ma- terials used in these experiments; they are often lumpy, and do not come in contact with more than a small portion of the soil to which they are add- ed. It does not appear probable that fertilizers applied t0 the soil come in direct contact with a greater portion of the soil particles than in these ex- periments; in fact, it is reasonable to believe that the contact is much less intimate in agricultural practice. It is found that while the capacity of soils to produce nitrates varies considerably, and may be affected greatly by carbonate of lime or other additions, the production of active nitrogen is less affected. That is to say, the quantity of active nitrogen furnished the plant appears to depend more upon the quantity and nature of the organic materials in the soil and on physical conditions than on the nature and composition of the soil. It thus becomes a matter of some importance to know the relative values of ammonical and nitric nitrogen as such. In table XI. we find the ammonical nitrogen to vary from 0.3 to 20.5 parts per million. In six of the twenty soils the quantity of ammonia pres- ent at the end of the period was 8 parts per million, which is more than the nitrogen present in the five soils very deficient in nitrogen. Ammoniacal nitrogen may thus be present even in well aired soils in considerable amounts. If plants depend entirely upon nitrates for nitrogen, the fertility of the soil should depend largely upon its ability to support the nitrifying organ- isms, and the availability of organic fertilizers would vary with the nitri- fying capacity of the soils to which they are applied. If both ammonia and nitric nitrogen were assimilated equally by plants, the fertility of the soil would bear little relation to its nitrifying power, since the production of active nitrogen seems to depend more upon the nature of the material than upon the character of the soil. It is more probable, however, that ni- tric and ammonia nitrogen are of unequal value to plants, varying with the nature of the plant, and perhaps depending upon the power of the soil to fix ammonia. The nitric nitrogen, being more soluble and little subject to fixation, is probably more easily absorbed than ammonia. The nitrifying capacity of a soil must, therefore, be of some influence upon its fertility, though not as much as if ammonia were totally unavailable. Unfortunately we have no quantitative estimations of the availability of ammonical nitrogen compared with nitric nitrogen under conditions ex- cluding nitrification of ammonia. In pot and field tests, in which more or less of the ammonia is nitrified, ammonia salts are not, as a rule, equal to nitrates. The difference has been ascribed to the beneficial effect of the sodium of sodium nitrate and the injurious effect of the acid residue of am- monium sulphate, but it may also be due to the incomplete nitrification of ammonia and the lower capacity of the latter to serve as nourishment for the plants under study. Wagner assigned the value 90 to the nitrogen of the ammonia salts, compared with sodium nitrate nitrogen as 100. (29) Wheeler found nitrogen in ammonium sulphate to have the value of 92.2 on a limed soil, and less than nothing on an unlimed acid soil, with the nitric nitrogen equal to 100 as the standard. It appears probable that ammoniacal nitrogen, as such, has a lower value for most cultivated plants than nitric nitrogen. Such being the case, the nitrifying capacity of the soil has some influence upon the crop value of the fertilizer nitrogen placed within it. SUMMARY AND CONCLUSIONS. (1) Ammonia and nitrates, which can be taken up by plants, and are here termed active nitrogen, are formed from the organic matter of the soil which cannot be absorbed by plants. (2) Soils vary considerably ‘in their ability to produce nitrates (nitri- fying capacity), but to a much less extent in their ability to produce active nitrogen. (3) Excess of water decreases nitrification down to practically zero in a water-logged soil, and also decreases the production of active nitrogen, though not to such an extent as of nitrates. (4) N0 relation could be observed between the increased production of nitrates due to calcium carbonate, and the acidity or basicity of the soils estimated by the methods described, though the greatest increase was effected on the most acid soil. (5) Although the addition of carbonate of lime increased the produc- tion of nitrates in most of the soils, the production of active nitrogen was affected thereby only to a slight extent. (6) Magnesium carbonate is less favorable to nitrification in the soil tested than calcium carbonate. _ (7) Nitrification was much greater in a limed acid soil than in the unlimed acid soil. (8) Phosphoric acid and potash had little effect upon the production of active nitrogen, though in some cases nitrification was affected con- siderably. (9) The formation of ammonia begins rapidly, and a large proportion of the change takes place the first week, under Texas conditions. Nitrifica- tion began the second week and reached its maximum in the third. (10) At the end of 56 days, under very favorable conditions, a large portion of the active nitrogen produced from cottonseed meal was still in the form of ammonia. (11) While the rank of nitrogenous fertilizers measured by the ni- trates formed varies according to the nature of the soil, the relative pro- duction of active nitrogen is much less’ variable and depends upon the na- ture of the material. This offers a method for comparing the values of different nitrogenous fertilizers. (12) The nitrogen removed by a crop of corn from pots was com- pared with the active nitrogen produced in jars. In most cases a greater quantity of nitrogen was taken up by the plants than would be produced in the jars, due to more favorable conditions in the pots for the transforma- tion of nitrogen to active forms. (13) Nitrogen content of the crop, as a rule, increases with the active nitrogen produced in the soil. (30) (14) All soils yielding less than 7 parts per million of nitric nitrogen, or 9 parts of active nitrogen in the jars, are highly deficient in the pot tests. In no case is the crop larger than 8 grams, and the addition of ni- trates increases the crop four-fold or more. (15) Soils yielding 7 to 22 parts per million of nitric nitrogen, 0r 9 to 27 parts of active nitrogen, appear to be deficient in nitrogen. (16) Of nine soils yielding 27 parts per million of active nitrogen in the jars, four appear to supply sufficient nitrogen to the crop, two respond slightly to nitrates, while three respond considerably. (17) The soils containing 0.02 per cent nitrogen were very deficient in nitrogen and produced the smallest quantities of active nitrogen. On an average, the production of active nitrogen increases with the nitrogen con- tent of the soil, though the results with individual soils were irregular. (18) Six soils containing an average of 0.12 per cent total nitrogen contained an average of 59 parts per million of active nitrogen, this being 5 per cent of the total. Six soils, with an average nitrogen content of 0.8 per cent, and five with an average of 0.026 per cent, contained 21 and 7 parts per million of active nitrogen, being 2.5 and 2.7 per cent of the total. The nitrogen of soils containing high percentages appears to be more available than that containing low percentages. (19) The production of active nitrogen in the soil can probably be developed into a method for the determination of the needs of the soil for nitrogenous fertilizers. (20) Certain of the soils subjected to study contained a considerable proportion of their active nitrogen in the form of ammonia. (21) The ammonia of soils appears to deserve considerably more at- tention than it has received. (31) Wgqvr-flfifw. ~ .