TEXAS AGRICULTURAL EXPERIMENT snmow BULLETIN NO. I81. OCTOBER, 1915. DIVISION OF CHEMISTRY Oxidation of Organic Compounds in the Soil POSIOFFICE: COLLEGE STATION, BRAZOS COUNTY, TEXAS AUSTINATflTEXAS VON BOECKMANN-JONES CO., PRINTERS‘ [Blank Page in Original Bulletin] TEXAS AGRICULTURAL EXPERIMENT 5111119115111 BULLETIN NO. 181. . OCTOBER, 1915. DIVISION OF CHEMISTRY Qxidation of Qrganic Compounds in the Soil BY G. S. FRAPS, Ph. D., CHEMIST IN CHARGE; STATE CHEMIST POSTOFFICE: COLLEGE STATION, BRAZOS COUNTY, TEXAS AUSTIN, TEXAS VON BOECKMANN-JONES 00., PRINTERS, 1915 AGRICULTURAL AND MECHANICAL CULLLUL ur lnAAo W. B. BIzzELL, A. M., D. C. L., President TEXAS AGRICULTURAL EXPERIMENT STATION ‘ BOARD OF DIRECTORS} 5| O I “WP 7mg‘ '. WILLIAMS, Paris............. . E..BATTLE, lflarlin ........ .. C. BREIHAN, Bartlett ..... .. F. KUBENA, P‘ayetteville ..... .. EA. MILLER, JR., Amarillo.. €“€"1 11> N I. GUION, President, Ballinger ...................... .. . HART, Vice President, San Antonio ............. .. . . ASTIN, Bryan .................................................. .. DAvIDSoN, Cuero ........................................... .. ................................... ..Term expires‘1919 .................. ..Term expires 1919 ......... ..Term expires 1919 .....Term expires 1917 ................ .. ..Term expires 1917 . ........................ ..Term expires 1917 ........................... ..Term expires 1921 ........................ ..Term expires 1921 Term expires 1921 MAIN STATION COMMITTEE L. J. HART, Chairman J. S. WILLIAMS \V. A. MILLER, JR. GOVERNING BOARD, STATE SUBSTATIONS P. L. DowNs, President, Temple ............................ .. CHARLES RDGAN, Vice President, Austin .............. .. W. P. HOBBY, Beaumont ......................................... .. J. E. BOOG-SCOTT, Coleman... ................................. .. ............................................ ..Term expires 1919 ............... ..Term expires 1917 ...... ..Term expires 1917 ............ ..Term expires 1921 *STATION STAFF ADMINISTRATION B. YOUNGBLOQD, M. S., Director A. B. CQNNER, B. S., Vice Director CIIAs. A. FELKER, Chief Clerk A. S. WARE, Secretary DIVISION OF VETERINARY SCIENCE M. FRANcIS, D. V. S., Veterinarian in Charge _ H. SCHMIDT, D. V. M., Veterinarian DIVISION OF CHENIISTRY G. S. FRAPS, Ph. D., Chemist in Charge; State Chemist R. H. RIDGELL, B. S., Assistant Chemist FRANK HoDGEs, B. S., Assistant Chemist W. T. P. SPRoTT, B. S., Assistant Chemist . DIVISION OF HORTICULTURE H. NESS, M. S., Horticulturist in Charge W. S. HOTCHKISS, Horticulturist DIVISION OF ANIMAL HUSBANDRY J. C. BURNS, B._S.,_Animal Husbandman Feeding Investigations. J. M. JQNES, A. M., Animal Husbandman, Breeding Investigations DIVISION OF ENTOMOLOGY F. B. PADDOCK, B. S. E.,_ Entomologist in Charge; State Entomologist _ O. . CouRTNEv, B. S., Assistant Ento- mologist DIVISION OF AGRONOMY _ A. B. CoNNER, B. S., Agronomist in ‘Charge A. H. LEIDIGH, B. S., Agronomist H. H. JoEsoN, B. S., Agronomist _ LOUIS WERMELSKIRCHEN, B. S., Agronomist DIVISION OF PLANT PATHOLOGY AND PHYSIOLOGY F. H. BLODGETT, Ph. D., Plant Pathologist and Physiologist in Charge N. D. ZUEER, B. S., Fettow. **DIVISION OF FARM MANAGEMENT REx E. WILLARD, M. S., Farm Management Expert in Charge DIVISION OF POULTRY HUSBANDRY R. N. HARVEY, B. S., Poultrgman in Charge DIVISION OF FORESTRY J. H. FOSTER, M. F., Forester in Charge; State Forester DIVISION OF FEED CONTROL SERVICE JAMES SULLIvAN, Executive Secretary CHAS. A. FELKER, Chief Clerk J. H. RooERs, Inspector . H. WOOD, Inspector . H. WOLTERS, Inspector . D. PEARcE, Inspector . M. WICKES, Inspector T. B. REESE, Inspector SUBSTATION NO. 1: Beeville, Bee County E. _E. BINFORD, B. S., Superintendent SUBSTATION NO. 2: Troup, Smith County W. S. Horcnxiss, Superintendent SUBSTATION NO. 3: County N. E. WINTERS, B. S., Superintendent SUBSTATION NO. 4: County H. H. LAUDE, B. S., Superintendent SUBSTATION NO. 5: Temple, Bell County A. K. SHORT, B. S., Superintendent SUBSTATION NO. 6: County T. W. BUELL, B. S., Superintendent SUBSTATION NO. 7: Spur, Dickens County R. E. DICKSON, B. S., Superintendent Lubbock, Lubbock sees Angleton, Brazoria Beaumont, Jefferson Denton, Denton SUBSTATION N0. 8: County V. L. CORY, B. S., Superintendent SUBSTATION NO. 9: Pecos, Reeves County J. W. JACKSON, B. S., Superintendent SUBSTATION NO. 10: (Feeding and Breed- ing Substation) College Station, Brazos County T. M. REDDELL, Superintendent SUBSTATION NO. 11: Nacogdoches, Nacog- doches County G. T. McNEss, Superintendent _ D. T. KILLOUGH, B. S., Scientific Assistant “SUBSTATION NO. 12: Chillicothe, Harde- man County R. \V. EDWARDS, B. S., Superintendent CLERICAL ASSISTANTS STATION J. M. SCI-IAEDEL, Stenographer W. F. CHRISTIAN, Stenographer ELIZABETH WALKER, Stenographer J. L. COTTINGHAM, Stenographer C. L. DURST, Mailing Clerk *As of October 1, 1915. **In Cooperation with FEED CONTROL SERVICE DAISY LEE, Registration Clerk E. E. KILBURN, Stenogra her WILLIE JoRNsoN, Tag C erk he United States Department of Agriculture. TABLE OF CONTENTS. PAGE Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .' . . . . . . 5 Study by Means of Loss 0n Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . .' 6 Study by Means of Carbon Dioxide Formed . . . . . . . . . . . . . . . . . . . . 8 Comparison of Various Materials . . . . . . . . . . . . . . . . . . . .1 . . . . . . . . . . 9 Effect of Nature of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Oxidation of Soil Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18 Effect of Quantity ‘of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Eifeot of Method of Adding Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Effect- of Carbonate of Lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21 Description of Soils Usedn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22 Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._ . . Q . . . . . 427 Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27 [Blank Page in Original Bulletin] OXIDATION OF ORGANIC MATTER IN THE SOIL BY G. S. Fairs, CIIEMIsT Ix CHARGE, STATE CHEMIST. The oxidation of organic matter in the soil is a matter of consider- able agricultural importance. Ammonia and nitrates are prepared for the use of plants, in such oxidation, and the carbon dioxide produced is also believed to aid in the solution of mineral plant food. The organic matter modifies the physical properties of the soil, and its destruction or loss from the soil may give rise to changes in physical character. The oxidation of organic matter containing nitrogen could be studied indirectly by means of the nitrates and ammonia. produced. We might assume that the oxidation of the carbon proceeds at the same rate as the oxidation of nitrogen. We would not, however, be justified in the assumption that the production of nitrates alone and the oxidation of organic carbon proceeds at the same rate, since ammonia is not imme- diately oxidized to nitrates. The direct study of the changes in organic matter or carbon in the soil is more satisfactory than any assumption. A considerable amount of work upon the oxidation of organic matter in the soil has been done by W 0lln_y, and is reported in his book upon the subject (Wollny—-Die Zersetzuirtg der Orgainisclzeni Stofie, 1896). Most of the experiments cited in W ollny’s work were carried on with soils placed in glass tubes or similar vessels, through xvhich a current of air was drawn to take out the carbon dioxide. Although such experi- ments are well adapted to estimate carbon dioxide, obviously, such con- ditions do not prevail in the soil, and while it» is possible that \Vollny’s conclusions may apply to the soil under natural conditions, yet it is also possible that the oxidation may proceed somewhat differently in soils less well aerated. It is known, for example, that nitrification in a liquid culture is not the same as nitrification in the soil. Cottonseed meal will putrefyr in soil in flasks stoppered with cotton wool, while in glass jars, the same mixture xvill nitrify. A soil in a glass tube through which a current. of air is drawn will be better supplied with oxygen than a soil under natural conditions, and therefore organic matter may be oxidized differently in it. Oxidation of organic matter in the soil will depend upon the nature of the organic material oxidized, and the ability of the soil to support the oxidizing organisms, in addition to other variable influences, such as the kind and relative numbers of bacteria, temperature, the water content, the quantity of oxygen in the soil, etc. Just as the relative ability of the soil to support nitrifying organism has been termed its nitrifying caper-city], so the relative power of the soil to sup-port oxidizing organisms may be termed its oxidation cajracity. The nitrifying capac- ity, the oxidation capacityand the capacity of the soil to convert am- monia into nitrates and ammonia are to a certain extent related, espe- 6 TEXAS AGRICULTURAL EXPERIMENT STATION. eially the two latter. They are not necessarily the same in the same soils, however, and do not necessarily vary in the same Way under the influence of different factors. STUDY BY BIEANS OF LOSS ON IGNITION. The estimation of the loss on ignition of a soil is well known not to be a satisfactory indication of the organic matter contained in the soil. The quantity of organic matter is sure to be less than the amount of loss on ignition. but can not be greater than this amount. Soils always contain water of combination or hydration, which is not lost at 100° C. but lost on ignition. A clay may thus have a high loss on ignition, but contain little organic matter. If we work on the same soil, however, making various additions to it, the loss on ignition may be used as an approximate measure of the quantity of organic matter lost or gained. Such results are compara- tive, as different samples of the same soil may be assumed to contain the same quantities of water of hydration. The method can not be claimed to have a high degree of accuracy. Réiaulis with the M eth/odr-The loss on ignition was determined in a number of the mixtures of soil and organic matter prepared for the study of the loss or gain of ammonia-soluble organic matter of the soil. (See Bulletin 129.) In order to secure comparable results, the loss on ignition has been calculated to the percentages of the ignition residue of the soil or mixture. This is necessary, for the ignition residue should not vary, xyhile the quantity of water and loss on ignition will vary with the quantity of organic residues present. The method of calcu- lation is shown in Table 1. TABLE b-METHOD OF CALCULATION. t “Soil s95 l Soil 914 Ignition residue In 100 gm. soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97.46 97.89 In 4 gm. excrement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 l 0.20 Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 . e6 l 98.09 Loss on ignition - ‘ In 100 gm. soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.90 1.74 In 4 gm. excrement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.53 . 3.53 Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.43 l 5.27 Loss on ignition calculated to 100 gm. ignition residues . . . . . . . . . . . . . . 5.56 t 5.37 1 Intervals 0f T-ime.—Several mixtures of soil with excrement were pre- pared, kept moist, and a jar of each soil mixture was dried for analysis ' at various eriods of time. The results are resented in Table 2. The a | o u a p organic matter disappears rapidly (luring the first few weeks. After that time the loss on ignition is irregular, and it is difficult to follow the changes in the organic matter by this method. In this work, 20 grams excrement was mixed with 500 grams soil. OXIDATION or ORGANIC COMPOUNDS IN THE SoiL. 7 TABLE 2——-LOSS ON IGNITION AT VARIOUS PERIODS, IN PERCENTAGE OF IGNI- TION RESIDUE. Soil 895 Soil 914 Soil 958 Original mixture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.55 5.37 11.87 After 2 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.35 4.72 11.20 After 4 Weeks . . . . . . . .. _ 5.09 . . . . . . . . .. 11.41 After 5 Weeks. .. 5.16 4.64 11.48 After 7 weeks. .. 4.74 4.47 10.79 After 9 weeks. .. 4.26 4.23 10.72 After 11 weeks. .. 4.76 3.97 10.69 After 13 weeks. .. 4.94 4.43 10.68 After 15 Weeks. .. 5.03 4.52 11.21 After 19 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. 4.80 4.04 10.81 After 21 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.89 4.42 11.23 After 23 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.97 4.65 10.64 After 25 weeks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.31 4.12 10.15 b N aft/are of flla»ter~ial.—'.[‘alile 0 shows the loss on ignition of soils which received various additions, after standing while moist at room temper- atures for 14 weeks and also the original dry mixture. In Table 4 the. loss on ignition of the original soil is subtracted, showing losses due to the added material. The loss on ignition of the original mixtures is calculated as shown in Table 1, from the composition of the soil and of the organic substances used. Analyses of the soils are given in Ta.ble 22, a.nd description on page 24. TABLE 3—LOSS OF ORGANIC MATTER FROM VARIOUS MATERIALS MEASURED BY LOSS ON IGNITION IN PERCENTAGE OF IGNITION RESIDUES. Lufkin _ Orangeburg Orangeburg Fine Sand. Fine Sandy Loam. Fine Sand. Added Soil 895 Soil 958 Soil 885 Original After 14 Original After 14 Original After 14 Mixture. Weeks. Mixture. Weeks. Mixture. Weeks. N0 addition . . . . . . . . . . 1.97 1.99 Blood . . . . . . . . . . . . . .. 5.51 3.44 Excrement . . . . . . . . . . . 5.56 4.80 Cottonseed Meal. . . . . 5.54 2.91 Meat . . . . . . . . . . . . . . . . 4.01 3.06 Rice hulls . . . . . . . . . . . . 5.31 2.93 Bat guano . . . . . . . . . .. 5.21 4.62 Tankage . . . . . . . . . . . . . 4.35 2.83 Wheat bran . . . . . . . . . . 5.46 3.05 Corn chops . . . . . . . . . . 5.61 2.67 Wheat shorts... . . . . . . 5.48 2 72 TABLE 4—LOSS ON IGNITION DUE TO ADDED ORGANIC IVIATERIAL. Lufkin _ Orangeburg Orangeburg ‘ Fine Sand. Fine Sandy Loam. Fine Sand. Soil 895 Soil 958 Soil 885 _ _ After _ _ After _ _ After Origi- 14 Per cent Origi- 14 Per cent Origi- 14 Per cent nal. Weeks. l Lost. nal. Weeks. Lost. nal. “leeks. Lost. I l l Blood . . . . . . . . .. 3.54 1.45‘ 59 3.85 1.24 68 3.55 1.26 64 Excrement . . . . .. 3.59 2.81 22 3.90 2.91 25 3.58 3.03 15 Cottonseed meal. 3.57 0.92 74 3.87 .52 87 3.54 .95 73 Meat . . . . . . . . . .. 2.04 1.07 47 2.45; 81 67 2.96 1.12 62 Rice hulls . . . . . .. 3.34 0.94 72 . . . . . ..1 . . . . . . . . . . . . . . . . . . . ... . . . . . ..i . . . . . .. Batguano . . . . .. 3.24 2.63 19 . . . . . ..l . . . . . . . . . . . . . . . . . . . ..' . . . . . ..I . . . . . .. Tankagc . . . . . . . . 2.38 0.84 65 . . . . . . . . . . . . . . . . . . . . . . . . . . . .‘ . . . . . . . . . . . . . . Wheat bran..... 3.49 1.06| 70, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Corn ch0ps...... 3.64 0.68 81j . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Wheat shorts... 3.51 0.73 79i . . . . . Al: . . . . . . . . . . . . . . . . . . . . . . . . l!‘ . . . . . .. . I I l 8 Texas AGRICULTURAL EXPERIMENT STATION. For the results of the experiments, see Tables 3 and 41. It would appear from this experiment that cottonseed meal, corn chops, rice hulls, and wheat shorts, are the most easily oxidized of the materials tested, from 7'2 t0 81 per cent being oxidized in 14 Weeks. Consider- ing the woody nature of rice hulls, it is strange that it is so easily oxidized, and other experiments may not confirm this result. Meat, blood, and tankage, are less easily oxidized than are the vegetable mate- rials, 17 to 68 per cent being lost. Excrement, as could be expected, is oxidized slowly (15 to 22 per cent). Bat guano was also oxidized sloyvly. The period of this experiment was from October 17 to January 31. The jars were in an unheated basement. Without doubt, the temper- ature of the basement did not fall as low as the outside temperature of the air. Cottonseed meal, which is largely used as a fertilizer in Texas, would thus be oxidized fairly rapidly even during cool weather. Oxidation of a.ll the materials was more energetic in soil 958, Orange- burg fine sandy loam. Soils 895, Lufkin fine sand, and 885, Orange- burg fine sand, are apparently equal. ' STUDY OF OXIDATION BY MEANS OF THE CARBON DIOXIDE PRODUCED. In these experiments, 500 grams soil was mixed with the organic material and water, and placed in a. precipitation jar. The jar was placed in an air-tight vessel, purified air drawn through at various intervals, the carbon dioxide absorbed by soda lime, and weighed. The details of the method of procedure are as follows: The apparatus consisted of a precipitation jar placed inside of a \Vitt’s filtering jar, absorption trains leading to and over from the filtering jar and an aspirator to draw a current of air through it. The funnel of the filtering flask was removed and a tightly fitting one-hole rubber stopper was paraffined into the opening in the cover. One end of a glass tube, bent at a wright angle, was run through the hole in the stopper down to within a quarter of an inch of the surface of the soil, which is placed in the precipitating jar. To the other end of this tube is connected a train consisting of a spiral filled with sulphuric acid, a U tube filled with soda-lime, a U tube filled wth pumice stone and sul- phuric acid, this train being used to purify the air drawn into the jar. Into the side tube of the Witt jar was fitted the short end of a piece of glass tubing, bent to a right angle, and the joint made air-tight with sealing wax. The long end of the tube passed close to the side at the bottom of the filtering jar, in order to prevent carbon dioxide from collecting and remaining in the bottom of the jar. To the side tube of the filtering jar was connected an absorption train consisting of a sulphuric acid spiral, a U tube filled with pumice stone and sul- phuric acid, two U tubes filled with soda-lime and a U tube filled with pumice stone and sulphuric acid, to absorb any water given up by the soda-lime tubes, and U tube filled one side with soda-lime and the other with calcium chloride to prevent any carbon’ dioxide or water from working backward. Then followed the aspirator. After the air OXIDATION or ORGANIC COMPOUNDS IN THE SoIL. 9 had been drawn through the apparatus, thetubes were carefully wiped, allowed to stand for a few minutes, and Weighed—a U tube which had been similarly wiped and handled being used as a counterpoise. The jars when not connected with the train were kept tightly closed. The conditions of our work are thus more nearly like natural soil conditions than those of Wollny. No air was drawn through the soil. There is, of course, risk of accumulation of carbon dioxide within the pores of the soil. Experiments described later showed, however, that any carbon dioxide held in this way would not affect the conclusions. Soil conditions are, however, more favorable to oxidation in these experiments than in the natural soil, as pointed out in connection with the nitrification studies. (Texas Bulletin 106.) COMPAIHSON OF VARIOUS BIATERIALS. First Series-Jn this series of experiments, 2.5 grams material and water equal to one-third the saturation capacity of the soil was mixed with 500 grams soil. The soil used, No. 1133, is Norfolk fine sand, from Franklin county, and contains .02 per cent. nitrogen and pro- duces one-fourth hale cotton or 15 bushels co-rn. For analysis see Table 22. TABLE 5—GRAMS CARBON DIOXIDE FORMED IN THE SOIL. Cotton- N0 '5'?“ seed‘ Addi- Manure. Wheat Corn Corn Meal. tion. Bran. Chops. Cobs. Carbon dioxide at the end of period (total 24 hours) . . . . . . . . . . . . .4519 .0131 .1248 . . . . . . . . . . . . . . . . . . . . . . . . Carbon dioxide at the end of period (total 48 hours). . . . . , . . . . ._ . . . . . . . . . . . .0168 . . . . . . . . .4879 .3082 .2220 Carbon dioxide at the end of period ' otal hours) . . . . . . . . . . . . .3589 . . . . . . . . .3802 .5203 .4156 . . . . . . . . Carbon dioxide at the end of period (total 96 hours) . . . . . . . . . . . . , .4546 .0149 .1901 . . . . . . . . . . . . . . . . .2193 Carbon dioxide at the end of period (total 120 hours) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5066 .4655 . . . . . . . . Total formed (4 or 5 days). . . .1 .2654 .0448 0.6951 1 .4148 1.1893 0.4413 The results of this experiment are given in Table 5. This experi- ment was conducted during the month of ill-arch. Oxidation of the organic material begins very rapidly. Within the first 24 hours, nearly 0.5 grams carbon dioxide was formed from cotton- seed meal. Since this meal contained approximately 1.15 grams car- bon, equivalent to 5.2 grams carbon dioxide, this amount represents about ten per cent. of the carbon of the meal. Nearly 30 per cent. was oxidized in four days. The wheat bran is oxidized even more rapidly than the cottonseed meal. The order of oxidization in this ex- periment is as follows: Bran (first), cottonseed meal, corn chops, manure, cobs. Second Series.—The object of this series was to compare the oxida- tion of cottonseed meal, manure, and corn cobs for a longer period of time than in the preceding experiments. 10 flfnxas AGRICULTURAL EXPERIMENT STATION. Five hundred grams of soil No. 1.135 and 2.5 grams organic material Were mixed With 50 c.c. water, placed in precipitation jars, and the jar placed in the apparatus for the collection of carbon dioxide. Every day the accumulated carbon dioxide was washed into the absorption apparatus by drawing two liters of air through the apparatus. The soil used is Norfolk fine sandy loam of Franklin county, and contains .035 per cent. nitrogen, 12 parts per million of active phos- phoric acid, 216 parts per million of active potash, and produces one- half bale cotton or 20 bushels of corn. (For analysis, see Table 22. TABLE 6—~PRODUCTION OF CARBON DIOXIDE (IN GRAMS). Cotton- Days. No seed Manure. Corn Addition. Meal. Cobs. l April 22 (24 hours) . . . . . . . . . . . . . . . . 1 0298 .1673 .0673 0453 April 23 . . . . . . . . . . . . . . . . . . . . . . . . . . 2 0096 .3258 .0779 0704 April 24 . . . . . . . . . . . . . . . . . . . . . . . . . . 3 0034 .2385 .0696 0257 April 25 . . . . . . . . . . . . . . . . . . . . . . . . . . 4 0253 . 2438 .0419 0859 April 26 . . . . . . . . . . . . . . . . . . . . . . . . . . 5 0147 .3137 .0771 1070 April 27 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 0059 .2595 .0467 0553 April 28 . . . . . . . . . . . . . . . . . . . . . . . . . . 7 0062 .1919 . 0359 0810 April 29 . . . . . . . . . . . . . . . . . . . . . . . . . . 8 0108 .1662 .0308 0684 April 30 . . . . . . . . . . . . . . . . . . . . . . . . . . 9 0049 .0796 .0244 0423 ay . . . . . . . . . . . . . . . . . . . . . . . . . . 10 0043 .0600 .0186 0311 May 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 11 0039 .0500 0208 0340 May 3 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 0077 .0597 0202 0289 May 4 . . . . . . . . . . . . . . . . . . . . . . . . . . 13 0048 .0823 0243 0355 May 5 . . . . . . . . . . . . . . . . . . . . . . . . . . 14 0074 .0696 0231 0384 May 6 . . . . . . . . . . . . . . . . . . . . . . . . . . 15 0116 .0567 0195 0422 The results of the experiment are presented in table 6. Varia- tio11s in the quantity of carbon dioxide produced from day to day are marked. These are, to some extent, related to changes in tempera- tures, for the apparatus was in all cases kept at jroom templerature. Oxidation begins rapidly and nearly reaches the maximum in forty- eight hours, though there is a second maximum at the end of four (lays. Thirty-eight and eight-tenths per cent. (38.8%) of the carbon of cot- tonseed meal, 10.1 of the manure, and 8.8 of the corn robs, was oxidized the first Week. Fifty-twp and six-tenths per cent. (52.6%) of the car- bon of the cottonseed meal, 14.1 of the manure. and 15.0 of the corn cobs, Were oxidized (lllT111g‘_ll']€ two weeks. At the end of fifteen days, nitrates and ammonia were estimated in all the jars, the nitrates by the Tiemann-Schulze method, and the ammonia btv distillation with magnesium oxide, as described in Bulle- tin No. 106 of this Station. (See '.l‘a.ble '7.) OXIDATION or ORGANIC COMPOUNDS IN THE SOIL. 11 TABLE 7—-PRODUCTION OF NlTRlcDigggnAEMMoNlA NITROGEN AND CARBON N0 Cotto - Addi- seedn Manure. Corn tion. Meal. Cobs. Milligrams nitric nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 74.0 11.0 14.0 Milligrams ammonia nitrogen . . . . . . . . . . . . . . . . . . . . . . . 1.6 37.1 7.8 2.2 Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7.9 114.1 18.8 16 Percentage of carbon oxidized, first week . . . . . . . . . . . . . . . . . . . . . 38.8 10. 1 8.8 Percentage 0f carbon oxidized, second week . . . . . . . . . . . . . . . . . . . 13.8 4.0 6.2 Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 52.6 14.1 15.0 Percentage nitrogen oxidized to nitrates . . . . . . . . . . . . . . . . . . . . . . 37.6 8.3 . . . . . . . . Percentage nitrogen oxidized to ammonia . . . . . . . . . . . . . . . . . . . . . 19.7 10.9 . . . . . . . . Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.3 t 19 2 t 100 (a) The oxidation which took place during this experiment was very vigorous. Nearly 40 per cent. of the cottonseed meal was oxidized the first week. It is known ‘that the nitrogen of cottonseed meal must be changed to ammonia and nitrates before plants can take it up. This change takes place rapidly, and it‘ the meal is placed in the ground at the time of planting, some ammonia. and nitrates are formed, ready for the young plant, by the time the seed sprouts and begins to come up. The oxidation of the nitrogen of both the cottonseed meal and the manure takes place at a somewhat greater rate than the production of carbon dioxide. The protein must be more easily oxidized than the non-protein materials, or else the protein is only partly oxidized, car- bonaceous portions remaining after the nitrogen has been convert-ed into ammonia and nitrates. Third Seri0s.-—'l‘he object of this series was to compare the carbon dioxide produced from cottonseed meal, dung and humic acid dur- ing long periods of time. As in the preceding experiment, five hun- dred grams of soil (No. 1290) were mixed with 2.5 grams organic ma- terial and 50 c.c. water. Eight jars of each mixture- were prepared. In each jar a test tube with a hole in the bottom was inserted to the depth of an inch. One jar of each material was placed in the carbon dioxide apparatus. The others were placed in an unused room", in a dark" cupboard. At the end of each week, water was added through the test tube to replace that lost on evaporation. The jar in the carbon dioxide apparatus was taken out, the apparatus ventilated, and a new jar of soil placed therein. Nitrates and ammonia. were estimated in the soil taken out in the old jar. A fresh portion of soil was thus used in the experiment every week. Soil X0. 1290, used in this Work, is Norfolk sand from Anderson county, and contains 0.0.2 per cent. nitrogen. (See table 12 for analysis.) The humic acid was prepared by solution in ammonia, from a soil from South Dakota. The excre- ment consisted of solid and liquid excrement, sun dried. Carbon dioxide was estimated every day for the first thirteen days; after that time, on alternate days only. This was done on account of the decreased rate of evolution of carbon dioxide. production of carbon dioxide is shown in Table 9. 12 CFExAs AGRICULTURAL EXPERIMENT STATION. TABLE 8-—-CARBON DIOXIDE IN GRAMS PRODUCED FROM SOIL AND MIXTURE. C0tton- t Date. seed Dung. Humi Nothing Meal. i Acid. May 12 End of first 24 hours . . . . . . . . . . . . . . . . . . . . . . . . .2460 .0561 .0203 .0267 May 13 End of second 24 hours . . . . . . . . . . . . . . . . . . . . . 3166 0730 0166 .0355 May 14 End of third 24 hours . . . . . . . . . . . . . . . . . . . . . . . 2756 .0778 0162 0300 May 15 End 0f fourth 24 hours . . . . . . . . . . . . . . . . . . . . . . 2141 .0903 0161 0154 May 16 End of fifth 24 hours . . . . . . . . . . . . . . . . . . . . . . . 1954 1205 0153 0128 May 17 End of sixth 24 hours . . . . . . . .' . . . . . . . . . . . . . . . 1750 .0908 .0090 .0088 May 18 End of seventh 24 hours . . . . . . . . . . . . . . . . . . . . 1309 0744 .0050 0030 Total, first week . . . . . . . . . . . . . . . . . . . . . . . 5536 5829 .0985 1322 May 19 End of first 24 hours . . . . . . . . . . . . . . . . . . . . . . . . .0270 .0361 .0102 .0080 May 20 End of second 24 hours . . . . . . . . . . . . . . .. . . . . . . .0896 .0726 .0115 .0112 . May 21 End 0f third 24 hours . . . . . . . . . . . . . . . . . . . . . . . .1072 .0803 0138 .0017 May 22 End of fourth 24 hours . . . . . . . . . . . . . . . . . . . . . . .0985 .0621 .0114 .0057 May 23 End of fifth 24 hours . . . . . . . . . . . . . . . . . . . . . . . 0984 0530 .0212 0112 May 24 End of sixth 24 hours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . May 25 End of seventh 24 hours . . . . . . . . . . . . . . . . . . . . 1008 .0628 .0255 .0117 Total, second week . . . . . . . . . . . . . . . . . . . . . .5215 .3669 0936 .0495 May 27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0714 0535 0267 .0220 May 29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0616 .0594 0249 .0225 May 30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0438 .0376 0206 .0188 June 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0486 .0497 0290 .0229 Total, third week . . . . . . . . . . . . . . . . . . . . . . 2254 2002 1012 .0862 June 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0443 .0514 .0271 .0208 June 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0416 .0594 0275 .0207 June 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0331 .0388 .0202 0167 June 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0286 .0489 .0218 0155 Total, fourth week . . . . . . . . . . . . . . . . . . . . . 1476 1985 0966 .0737 gune . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 031g une . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01 June 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0209 .0300 0175 0131 June 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0267 .0268 0148 0179 Total, fifth week . . . . . . . . . . . . . . . . . . . . . . . 1097 1174 .0868 .0842 June 17 ...' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .0275 .0340 .0143 0129 June 19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0305 .0224 .0267 0160 June 21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .0215 0145 .0148 .0139 June 22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0169 0138 0185 .0131 Total, sixth week . . . . . . . . . . . . . . . . . . . . . . . .0964 0844 0743 .0559 l TABLE 9-—-WEEKLY PRODUCTION OF CARBON DIOXIDE. icottlin‘ D H ' Aldd s ung. c - Nlegal. tionl Carbon dioxide first week . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .5536 .5829 .0985 .1322 Carbon dioxide second week . . . . . . . . . . . . . . . . . . . . . . . . . 0.5215 .3669 .0936 .0495 Carbon dioxide third week . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2254 .2002 .1012 .0862 Carbon dioxide fourth week . . . . . . . . . . . . . . . . . . . . . . . . . 1476 1985 .0966 0737 Carbon dioxide fifth week . . . . . . . . . . . . . . . . . . . . . . . . . . . 1097 1174 .0868 .0842 Carbon dioxide sixth week . . . . . . . . . . . . . . . . . . . . . . . . . . 0464 0844 0743 .0559 Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6042 1.5503 .5510 .4817 The details of the experiment are presented in Talble 8. Weekly The production de- creases rapidly frorn the first week. especially xvith cottonseed meal. With hurnic acid, there is a more uniform evolution of carbon dioxide. With the soil alone, a decrease of production of carbon dioxide takes place in the second Week. OXIDATION OF ORGANIC COMPOUNDS IN THE SoIL. 13 When organic matter is mixed intimately with the soil, and during moderately Warm Weather, as during this experiment, the oxidation of such materials as cottonseed meal is very rapid. The bacteria of the soil lose little time in going into action to dispose of the organic ma- terial introduced. The oxidation is most rapid during the first Week, and decreases during succeeding Weeks. The quantity of carbon dioxide formed from the cottonseed meal in the two Weeks isabout 10 per cent. less than in the preceding experiment. The humic acid apparently decreased oxidation during the first Week. Whether the slight deficiency in carbon dioxide over the soil With no addition is due to an error on the experiment, or the nature of the humie acid, We Will not undertake to say. - The amount of carbon dioxide Which Would be produced from the carbon of the organic materials used in this experiment, if completely converted into carbon dioxide. is given in Table 10, together With the amount of carbon dioxide actflally produced each Week. By subtrac- tion from the original amount, the quantity remaining at the end of each 1V6@l\’ is ascertained. From these figures, the percentage of carbon oxidized each Week has hen calculated, based on the total quantity of added carbon present at the beginning of such Week. TABLE 10—-PERCENTAGE OF CARBON DIOXIDE FROM THE MATERIAL PRESENT AT THE BEGINNING OF EACH WEEK. Cottonseed Dung. Hurnic Meal. Acid. Substance equal to carbon dioxide added . . . . . . . . . . . . . . . . . . 4.21 3.67 3.57 Lost end first week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 .42 .45 ——.03 Balance at end of first week . . . . . . . . . . . . . . . . . . . . . 2.79 3.22 3.60 Per cent loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.7 12.3 0 Lost second week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 .32 .04 Balance at end second week . . . . . . . . . . . . . . . . . . . . . 2.32 2.90 3.56 Per cent loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16.8 10.0 1.1 Lost third week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 .11 .02 Balance third week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.18 2.79 3.54 Percentloss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.0 4.0 0.6 Lost fourth week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .06 .12 .02 Balance fourth week . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.12 2.67 3.56 Per cent loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 4. 0.6 . Lost fifth week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .03 ‘ .03 .003 Balance at end fifth week . . . . . . . . . . . . . . . . . . . . . . . 2.09 2.64 3.567 Per cent loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 1. . . . . . . . . Lost sixth week . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .04 .03 .02 Balance at end of sixth week . . . . . . . . . . . . . . . . . . . . . 2.05 2. 61 3.55 2. 1 . 0.5 Per cent loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . This table emphasizes the fact that the oxidation decreases rapidly after the first week. With cottonseed meal, the oxidation of each Week after the first is approximately one-half as much of that of the pre- ceding Week, until the oxidation becomes so slow as to be hardly dis-_ tinguishable from that of the soil material. The decrease in the oxidation ot the dung is less rapid, but still marked. Humic acid, as 14 TEXAS AGRICULTURAL EXPERIMENT STATION. could be expected, is very resistant towards the oxidation processes. Its oxidation during the first Week is a minus quantity, and during the second Week its oxidation is about one-tenth that of the dung. Nearly the same relation holds during the third and fourth Week. During the fourth and fifth Weeks, the oxidation is very slight, and hardly distinguishable from that of the organic matter of the soil. That is to say, in four Weeks, the added organic material Was oxidized doWn to very resistant organic bodies. Had this experiment been carried on under less favorable conditions, such as at a lower temperature, the oxidation Would probably not have been so rapid at first, and it Would have fallen off less rapidly‘. A longer time might also have been required to oxidize the material doWn to resistant substances similar to those- in the soil. EFFECT OF NATURE OF SOIL. The object. of this Work Was to ascertain What effect, if any, the nature of the soil had upon the production of carbon dioxide. The experiments Were carried out as previously described; namely, With 500 grams soil, 2.5 grams excrement, and Water to one-third the saturation capacity of the soil. For purposes of comparison, a standard soil Was chosen, Which Was placed in all series of experiments. Each soil Was run both With and Without the addition of excrement. The first experiment Was only continued for six days. We found later that all soils did not begin to oxidize at‘ the same rate, and those behind at the end of the first six days might begin to catch up during the second period. For this reason, the succeeding series of experi- ments Were carried on for longer periods of time. In all these series of experiments, carbon dioxide Was determined every day. We do not consider it necessary, however, to print all the figures secured. Summaries of the various series are given in Tables 11, 12. 13 and 14. Table 22 shoWs the composition of the soils used. TABLE l1—OXIDATION OF EXCREMENT IN VARIOUS SOILS. S _l Grams Per Pot. Relative Rank. 01 -—- N0. First Second ' Total First Second Total three three for six three three for six Days. Days. Days. Days. Days. Days. Set No. 1. 1956 With excrement . . . . . . . . . . . .1323 .1563 0.2886 100 100 100 N0 addition . . . . . . . . . . . . . . . .0455 .0270 .0725 100 100 100 CO) from excrement. . .. .0868 .1293 0.2161 100 100 100 880 With excrement . . . . . . . . . . . .0670 .1590 .2260 . . . . . . . . . . . . . . . . . . . . . . . . N0 addition . . . . . . . . ._ . . . . . . .0161 .0430 .0591 35 159 81 CO, from excrement . . . . . . . .0509 .1160 .1669 59 90 77 1128 With excrement . . . . . . . . . . . .0322 .0391 .0713 . . . . . . . . . . . . . . . . . . . . . . . . No addition . . . . . . . . . . . . . . . .0223 .0142 .0385 49 53 53 CQQ from excrement . . . . . . . .0099 .0249 .0348 11 19 16 897 With excrement . . . . . . . . . . . .1499 .1399 .2898 . . . . . . . . . . . . . . . . . . . . . . . . No addition . . . . . . . . . . . . . . . .0982 .0605 .1587 216 224 219 CO,from excrement . . . . . . . .0517 .0794 .1311 60 61 61 Set N0. 2. 1956 With excrement . . . . . . . . . . . .1144 .2069 .3213 100 100 100 No addition . . . . . . . . . . . . . . . .0520 .0220 .0740 100 100 100 CO2 from excrement . . . . . . . .0624 .1849 .2573 100 100 100 OXIDATION OF ORGANIC COMPOUNDS IN THE SoIL. 15 TABLE lb-OXIDATION OF EXCREMENTS IN VARIOUS SOILS——C0ntinued. s _l Grams Per Pot. Relative Rank. 0 Nd. First Second Total First Second Total three three for six three three for six Days. Days. Days. Days. Days. Days. 876 With excrement . . . . . . . . . . . .0307 .0212 .0519 . . . . . . . . . . . . . . . . . . . . . . . . N0 addition . . . . . . . . . . . . . . . .0137 .0083 .0220 26 38 30 CO, from excrement . . . . . . . .0125 .0129 .0254 20 7 10 938 With excrement . . . . . . . . . . . .1225 .2424 .3649 . . . . . . . . . . . . . . . . . . . . . . . . N0 addition . . . . . . . . . . . . . . . .0758 .0660 .1418 146 300 192 CO2 from excrement . . . . . . . .0467 .1764 .2231 75 95 87 1119 With excrement . . . . . . . . . . . .1132 .1950 .3082 . . . . . . . . . . . . . . . . . . . . . . . . N0 addition . . . . . . . . . . . . . . . .0792 .0263 .1055 152 119 143 CO2 from excrement . . . . . . . .0340 .1687 .2027 55 91 79 TABLE 12——PRODUCTION OF CARBON DIOXIDE IN SOILS. Grams Per Pot. Relative Rank. Soil ° ° ‘l’ Q N0. g E g‘ E 8 s; g E 5 I; . :5 . a E . U . f» . l; . s? =§ 11$.’ efi ~ 3Q sfi. vi‘. 13K ~—' mm 8m gm 5c: S ma: gcwsfzcu gCU S fiQ 53D F-fQ L2G a fifl 63G EEO éfl [3 1956 With excrement . . . . . . . . . . . .. .1165 .1392 .0605 .0886 .4048 .... .... .... .... .... No addition . . . . . . . . . . . . . . .. .0274 .0197 .0157 .0151 .0786 100 100 100 100 100 Difference . . . . . . . . . . . . .. .0891 .1195 .0448 .0728 .3262 100 100 100 100 100 1809 With excrement... .1143 .2283 .0933 .0873 .5232 No addition . . . . . . . . . . . . . . .. .0608 .0468 .0222 .0232 .1530 222 238 141 153’ 194 rDifierence . . . . . . . . . . . . .. .0538 .1815 .0711 .0641 .3702 60 152 149 88? 114 870 With excrement.............. .0798 .1747 .1089 .0645 .4279 No addition . . . . . . . . . . . . . . .. .0284 .0266 .0258 .0149 .0957 104 135 164 99 122 Difference . . . . . . . . . . . .. .0514 .1481l.0831 .0496 .3322‘ 58 124 185 68 102 Table 15 shows the relative production of carbon dioxide from the excrement added to the various soils, compared with soil X0. 1956 as a standard. These soils are arranged in the table in order according to their content of total Iiitrogen, beginning wvith the soil containing the least nitrogen. There are considerable differences in the first three days. which tend to equalize during the next succeeding three days so that the (litterences are less at the end of six days. The differences equalize still more (luring the succeeding six days, and for the period of twelve days, or of PlglltGtfil (lays, there is cornparativlex’ little differ- ence in the power of the different soils for producing carbon dioxide from the eiuarement, with three exceptions, soils Nos. 341, 1128, and 8'76. 16 TEXAs AGRICULTURAL EXPERIMENT STATION. TABLE l3—-PRODUCTION OF CARBONVDIOXIDE IN SOILS. Grams Per Jar. l Relative Rank. S011 First Second Total l First N0 six six twelve six Twelve Days. Days. Days. Days. Days. 1956 YVith excrenient . . . . . . . . . . . . . . . . . . .. .3506l .2525 . . . . . . ..! . . . . . . . . . . . . .. bH)addifi0n . . . . . . . . . . . . . . . . . . . . . .. .0582 .0344 0926~ 100 100 I)fiTerence . . . . . . . . . . . . . . . . . . . . .1 .2924‘ .2181 51051 100 100 ‘ l 341 VVith encyenient . . . . . . . . . . . . . . . . . . ..1 .1022 .2157 . . . . . . ..{ . . . . . . . . . . . . . . .. Pio addflnon . . . . . . . . . . . . . . . . . . . . . ..‘ .0460 .0660 1120; 79 121 Difference . . . . . . . . . . . . . . .1 . . . . . f .0552‘ .1497 2059} 19 40 857 with excrement . . . . . . . . . . . . . . . . . . .. .2201; .2998 . . . . . . .1 . . . . . . . . . . . . . . .. Phoaddihon . . . . . . . . . . . . . . . . . . . . . .. .0508. .0318 0826] 87 89 Difference . . . . . . . . . . . . . . . . . . . . . . 159s; .2680 4878j 58 85 1075 With excrement . . . . . . . . . . . . . . . . . . .. .8845! .3855 . . . . . . . .5 . . . . . . . . . . . . . . .. PJO addfiion . . . . . . . . . . . . . . . . . . . . . .. .1407} .1086 .2493 241 269 ]Difierence . . . . . . . . . . . . . . . . . . . .. .1938. .2750 46881 66 92 . ! 1202 with encrement . . . . . . . . . . . . . . . . . . .. .8055; .8855 . . . . . . .1 . . . . . . . . . . . . . . .. P90 addlUOH . . . . . . . . . . . . . . . . . . . . . .. .0690} .0893 1583‘ 118 171 Difference . . . . . . . . . . . . . . . . . . . . . .2855} .2458 4828i 81 95 i 1 1956 \Vifl1e3cymnent..., . . . . . . . . . . . . . . .. .3766_ .2209 . . . . . . ..l . . . . . . . . . . . . . . .. PJO addfllon . . . . . . . . . . . . . . . . . . . . . .. .0616; .0414 1030 100 100 I)flfixence . . . . . . . . . . . . . . . . . . . .. .3150 .1795 .4945 100 100' 114 With excrement . . . . . . . . . . . . . . . . . . .. .2588. .3700 . . . . . . . . . . . . . . . . . . . . . . .. bh)add1fi0n . . . . . . . . . . . . . . . . . . . . . .. .0754’ .0869 .16231 122 157 I)fiTerence . . . . . . . . . . . . . . . . . . . .. .1834i .2831 .4665 58 94 335 With excrement . . . . . . . . . . . . . . . . . . . . .3595 . . . . . . . . . . . . . . . . . . . . . . . . PR)addifi0n . . . . . . . . . . . . . . . . . . . . . .. .1833’ .0821 .2654 297 257 I)iflerence . . . . . . . . . . . . . . . . . . . .. .2500 .2774 52741 79 107 939 VVith e;cren1ent . . . . . . . . . . . . . . . . . . .. .2919; .4033 . . . . . . ..1 . . . . . . . . . . . . . . .. PJO addflion . . . . . . . . . . . . . . . . . . . . . .. .1466; .1089 2555‘ 238 248 I)ifierence . . . . . . . . . . . . . . . . . . . .. .1453‘ .2944 43971 46 89 1057 YVith excrenient . . . . . . . . . . . . . . . . . . .. .2891 .3368 . . . . . . ..\ . . . . . . . . . . . . . . .. N0 addition . . . . . . . . . . . . . . . . . . . . . . . .0792 .0772 1564; 129 152 Difference . . . . . . . . . . . . . . . . . . . . . .2092‘ .2595 4688] 66 95 TABLE l4—-PRODUCTION OF CARBON DIOXIDE IN SOILS. Grams Per Pot. I Relative Rank. l . i e 1 I - S011 ,4 l .5 l P90. .5 -5 1 E .5 § x Q 5 . w . . . . ._ . 0 .2 Q “ '7 -~ .2: B .3” LLQ cgfl , gfll iii gtfl ilafl Eqfl [QC 1956 YVith excren1ent........... .4801 25921 . . . . .. .2040 . . . . . . . . . . . . . . . . . . . . . . .. PJO addifion . . . . . . . . . . . . .. .0907 05941 1501 .0494 1995 100 100 100 I)ifierence . . . . . . . . . . .. .3894 19981 5892 .1546 7438 100 100 100 841 With excrement . . . . . . . . .. .1904 2950? . . . . .. .1820 . . . . . . . . . . . . . . . . . . . . . . .. P40 addifion . . . . . . . . . . . . .. .1029 0760! 1789 .0527 .2316 113 119 116 I)flTerence . . . . . . . . . . .. 0527] 1402 .1093 .2495 22 24 34 .0875 OXIDATION or ORGANIC COMPOUNDS IN THE SOIL.’ 17 TABLE 14—-PRODUCTION OF CARBON DIOXIDE IN SOILS—Continued. Grams Per Pot. _ Relative Rank. . l ~ a | S011 | x g , No' i _>< i; 3 i g >4 g a u: '55 vi ‘H vi m vi .3 vi 7: vi g w 0 o: ._, >> i >. '5 >> "g :>= r51; >. .._, >. _. >. E >= as 85 ‘s5 s-“IS e5 $5 #115 u. J3 a e a ° u. a m 876 With excrement. . .. . . . . . .. .1773 .3254 . . . . . .1868 . . . . . . . . . . . . . . . . . . . . . .. No addition . . . . . . . . . . . . . . .0283 .0337 .0620[ .0328 .0948 311 41 48 Difference . . . . . . . . . . .. .1490 .2917 .4407, .1540 .5947 38 48 8O 897 With excrement. . .. . . . . . . . .5776 .3068 . . . . . .l .1697 . . . . . . . . . . . . . . . . . . . . . . . . No addition . . . . . . . . . . . . . . .1719 .0833 .2552‘ .0761 .3313 189 170 166 Difference . . . . . . . . . . . . .4057 .2235 .6292} .0936 .7228 104 107 97 1128 With excrement . . . . . . . . . . . .1531 .2652 . . . . . . .1646 . . . . . . . . . . . . . . . . . . . . . . . . No addition . . . . . . . . . . . . . . .0737 .0527 1264i .0373 .1637 81 84 82 Difference . . . . . . . . . . . . .0794 .2125 .2919} .1273 .4192 20 50 56 TABLE .l5——RELATIVE PRODUCTION FROM EXCREMENT. Lab. 3 6 12 18 Per cent. No. Days. Days. Days. Days. Nitrogen 897 Norfolk fine sand, surface soil . . . . . . . . . . . . . . . . . . . . . . 104 107 97 .028 897 Norfolk fine sand, surface soil . . . . . . . . . . . . . . . . 60 61 . . . . . . . . . . . . .028 880 Austin fine sandy loam, subsoil . . . . . . . . . . . . . . . 59 77 . . . . . . . . . . . . .028 1956 Sand, Brazos county, surface soil. . ._ . . . . . . . . . . 100 100 100 100 .033 341 Susquehanna fine sandy loam, subsoil . . . . . . . . . . . . . . . 22 24 34 .04 341 Susquehanna fine sandy loam, subsoil . . . . . . . . . . . . . . . 19 40 . . . . . . . . . . . . . . 1119 Susquehanna fine sand, surface . . . . . . . . . . . . . . . 55 79 . . . . . . . . . . . . .058 857 Orangeburg fine sandy loam, subsoil: . . . . . . . . . . . . . . . 58 86 . . . . . . .050 1067 Susquehanna fine sandy loam, subsoil . . . . . . . . . . . . . . . 66 95 . . . . . . .058 870 Laredo fine sandy loam, subsoil . . . . . . . . . . . . . . 58 102 . . . . . . . . . . . . .061 1202 Victoria clay, surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 95 . . . . . . .066 938 Austin fine sandy loam, surface . . . . . . . . . . . . . . 75 87 . . . . . . . . . . . . .089 336 Susquehanna fine sandy loam, surface . . . . . . . . . . . . . . . 79 107 . . . . . . .099 1128 Houston clay, subsoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 50 56 .10 1128 Houston clay subsoil . . . . . . . . . . . . . . . . . . . . . . . . 49 53 . . . . . . . . . . . . .10 876 Wilson clay loam, subsoil . . . . . . . . . . . . . . . . . . . . . . . . . . 38 48 8O . 10 876 Wilson clay loam, subsoil . . . . . . . . . . . . . . . . . . . . 20 10 . . . . . . . . . . . . . 10 1809 Surface soil, Brazos county . . . . . . . . . . . . . . . . . . 60 114 . . . . . . . . . . . . .108 939 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 46 89 . . . . .. .13 114 Travis gravelly loam, surface . . . . . . . . . . . . . . . . . . . . . . 58 94 . . . . . . .13 1075 Laredo clay, subsoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 92 . . . . . . .195 In Bulletin N0. 106, we pointed out the fact (from a study of five soils only) that, While the nitrifying capacity of different soils may vary widely, the power- of the soil for activating nitrogen, exhibits much less differences. While the five soils varied from 100 to 5 in nitrifying capacity, the variattion in nitrogen activating capacity would varied only from 100 to-70. We apply the term nitrifying capacity to the ability of a soil t0 serve as a medium for the growth of the nitrify- ing organism compared with some other soil of good nitrifying ca- pacity’ taken as a standard. The two soils are provided with nitrify- ing materials and placed under conditions which are alike in other re- spects. Cottonseed meal was used as the source of nitrogen in this work. We apply the term of nitrogen activating capacity to the power of the soil to produce ammonia and nitrate from a nitrifying substance compared with a soil of good nitrogen activating capacity under the 18 TExAs AGWRIGULTURAL EXPERIMENT STATION. same conditions. We will also apply the term oxidation capacity to the ability of the soil to produce carbon dioxide from the excrement as used in the experiments compared With the standard soil. There is thus a great. variation in the nitrifying capacity of the soil, a much smaller variation in the nitrogen activating capacity of soils, and a still less variation in the oxidation capacity. There are, how- ever, some exceptions‘to this rule. Three of the seventeen soils were decidedly lower in oxidation capacity. These soils Were Nos. 341, 1128 and 8'76. Soil No. 341 is the subsoil of Susquehanna fine sandy loam, soil No. 1128 is the subsoil to Houston clay, and soil 8'76 is the sub- soil to Wilson clay loam. All three of these soils, therefore, are sub- soils of clay nature, which may account in part for their low oxidation capacity. Soil No. 876 shows a tendency to approach the normal oxi- dation capacity at the end of eighteen days, but soils Nos. 1128 and 341 are still low in this respect. Soil No. 1128 was used in some nitrification Work and showed practically no power Whatever to con- vert nitrogen into nitrate. The addition of carbonate of lime, how- ever, gave it a good nitrifying capacity. The low nitrifying capacity in this case is associated with the low oxidizing power. It Will be in- teresting to ascertain whether this is the case With other soils which show a low nitrifying capacity. OXIDATION or soIL CARBON. Table 16 shows the relative oxidation of the soil carbon compared with soil No. 1956 as a standard. The soils are arranged. in order of their nitrogen content, beginning with the ones containing the least nitrogen. This is also the probable order of their carbon content. The three-day period and six-dayr period are too short to secure comparative results. The twrelyre-dav period is better. 'I_‘here are decided differ- ences in the relative quantities of carbon dioxide produced from the soil carbon. TABLE I6—RELATIVE PRODUCTION FROM SOIL CARBON. Lab. l 3 5 12 18 Per cent. Ratio No. Days. Days. Days. Days. Nitrogen N:CO2 897 Norfolk fine sand, surface soil. . . .' . . . . . . . 189 170 166 .028 190 897 Norfolk fine sand, surface soil. . . .. . . . 216 219 . . . . . . . . . . . . .028 . . . . . . . . 880 Austin fine sandy loam, subsoil . . . . . . 35 81 . . . . . . . . . . . . .028 . . . . . . . . 1956 Sand, Brazos county, surface soil. . . 100 100 100 100 .033 100 341 Susquehanna fine sandy loam subsoil. . . . . . . 113 119 116 . . . . . . . . 100 341 Susquehanna fine sandy loam subsoil. . . . . . . 79 121 . . . . . . .04 100 1119 Susquehanna fine sand, surface . . . . . . 152 143 . . . . . . . . . . . . .058 . . . . . . . . 857 Orangeburg fine sandy loam, subsoil.. . . . . . . 87 89, . . . . . . .050 60 1067 Susquehanna fine sandy loam, subsoil . . . . . . 129 , 152; . . . . . . .058 85 870 Laredo fine sandy loam, subsoil . . . . . . 104 . . . . . . 122 . . . . . . .061 68 1202 Victoria clay, surface . . . . . . . . . . . . . . . . . . . . . 118 171 . . . . . . .066 86 938 Austin fine sandy loam, surface . . . . . . 146 192 . . . . . . . . . . . . .089 . . . . . . . . 336 Susquehanna fine sandy loam, surface . . . . . . ‘297 257 . . . . . . .099 86 1128 Houston clay, subsoil . . . . . . . . . . . . . . . 49 53 . . . . . . . . . . . . .10 . . . . . . . . 1128 Houston clay, subsoil . . . . . . . . . . . . . . . . . . . . . 81 84 82 .10 28 876 Wilson clay 10am, subsoil . . . . . . . . . . . 26 30 . . . . . . . . . . . . .10 . . . . . . . . 876 Wilson clay loam, subsoil . . . . . . . . . . . . . . . . . 31 41 48 .10 14 1809 Surface soil, Brazos C0 . . . . . . . . . . . . . . 222 . . . . . . 194 . . . . . . .108 60 939 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 248 . . . . . . .13 63 114 Travis gravelly loam, surface . . . . . . . . . . . . . . 122 157 . . . . . . .13 4O 1075 Laredo clay, subsoil . . . . . . . . . . . . . . . . . . . . . . 241 269 . . . . . . .195 48 OXIDATION OF ORGANIC COMPOUNDS IN THE SoIL. 19 The difierences in the production of carbon dioxide from the soil‘ carbon are due partly to the oxidation capacity of the soil and partly t0 the quantity and to the character of the organic material contained in the soil. For the purposes of further comparison, we have reduced the carbon dioxide produced in twelve days to terms of a soil contain- ing .033 per cent. nitrogen (No. 1956). This is given in the column headed “Ratio of nitrogen to carbon dioxide.” An examination of this ta.ble shows that the organic matter of some of these soils must be in a. more resistant form than in others. There are still decided differ- ences, the quantity of carbon dioxide produced ranging from 14 to 190. Since we have previously pointed out that the oxidation capacity of these soils for excrement is nearly the same (except Nos. 34-1, 1128, and 8'76), these diiferences must be due largely to the nature of the soil carbonaceous compounds. The soil carbon seems to more easily oxi- dized from the soils containing the smaller nitrogen percentages. Thus the average ratio N170. ‘For the three soils containing less than .04 per cent. nitrogen is 130, for the six soils containing .05 to .099 per cent. nitrogen is 81, and for the six soils containing over 0.1 per cent. nitrogen is 42. The number of samples is, of course, small to draw general conclusions, but the fact appears interesting. The table brings out clearly the fact that there are greater differ- ences in the capacity of the organic matter of the soil to be oxidized, than in the power of the soil to support the oxidizing organisms. EFFECT 0F QITANTITY OF IVATER. The object of this experiment was to (letermine the effect of the quantity of water present in the soil upon the production of carbon dioxide. As in previous experiments, 500 grams soil was used. with no addition except water, and with addition of excrement. Carbon dioxide xvas estimated every day. The water was added in two different ways. In one series of ex- periments, the soil was placed in a porcelain dish, the water adS0< wm ow . . . . . . 3 2 M2 m: N. N~ . . . . . .301» aézgwogm 0>$0< 502:2 00m 30mm 00. mm. mm; 2.0 .340, 8.0 .510 fiwm filo ....................005202 0N0 wofi $2 $0 $5. 0N4“ £0 0N0 0w.» 62:03 E184 09$ oo. 5 i? 2A2 ommmw 00.3 U“. C. 00.9 3.2 . . 135w 202$ o5». oizowno ma; 2w...“ 2e ww M2 S w 2.3 00.8 NTmA 00.2 ... .00.; o0 03x0 Ea 001507» 1N. m?n mwi m£- mi. ON. c7. -~ - . - - - - . | . . . . --o-wrw®=mw§ MI. mH. 9i: . SA .. wm. om. no. on. he; mo. on. . . .. mo; om. . . . . . ooA co; . . . . . . . . . . . . ...nwmo0n:$0,w o7 mo. om. om. um. mm. m7 wm. mm. . . . . . . . . . . . ...........Aw$0m $3. Wummw. %@.©. @%- .@@- £3. §@. @%- fifl- .... ...........~HUWO.~PTZ mo. oo. wo. S. mo. mo. 2 . S. 0o. . . . . . . . . . . . . 06¢. 022102.00 “ocoohwm mow mww oww 0% 2.0 Em 50m 0mm w: 0 .00w.t:m dfinsm downsm domnsm. .00B0:w .00fl0:w downflm 00255 0030mm v .8004 .8004 580A .5004 4000A .5004 600m 00E 000m 007A 3.50m 05h 4500A >20 zocmm 05h 350m 00E 300mm 05h >052 00E 023226 afimsd mhsnomcwhO 523x c0255 oofimd mccwsonvwcm mccmcunvmnm mccwanosvwsm 030.0% dfiom HO zoipmomioolfi HHMFH 25 OXIDATION OF ORGANIC COMPOUNDS IN THE SOIL. N-mN o o o ---- q n o o ~ noun .1 p - - u - - - - n-n o~¢-¢|-¢u--u-n-vh\&rwimw< omm . . . . www . . . . . .. own ohm 0mm . . . . . ...............smm~omo>$u< mm m2 m . . . . . . . . . w.» o? 3 3 3 . . . . . . £34 Qcewaai @334 255:2 5Q 3.8m vm. Nwd 2Q mo; mdim w“. S. hm. No. . . . . ..........@bSwmo2 mo; IA; M36 3s Ed 2w 8; we; mo; . . . . . .........E.E=m~ cowwod 8.8 Nfi . E . Se“ ma? Zinc £3 3 2 09mm 31$ . . . 35m ...E=€w Ea @1525 33m $42 n53 320m 2...: Nmfi 3A .8. ~ f; ... 59G a. oExO Ea mains?» §~Y¢ §fi' Qww- §o- 7o. .-.-...»-.-¢--¢.Mw@w@cx@2 no. 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