54"?!‘ * A . ‘ T RjYAT52-1029-(LOOO-L18O TEXAS AGRICULTURAL EXPERIMENT smnow ‘A. B. CONNER, DIRECTOR COLLEGE STATION. BRAZOS COUNTY, TEXAS BULLETIN NO. 400 DECEMBER, 1929 DIVISION OF CHEMISTRY THE BASICITY OF TEXAS SOILS AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T. O. WALTON. President STATION STAFF’; ADMINISTRATION: A. B. CoNNER, M. S., Director R. E. KARPER, M. S., Vice-Director CLARIcE MIxsoN, B. A. Secretary M. P. HOLLEMAN, JR., Chief Cler J . K. FRANcKLow, Assistant Chief Clerk CI-IEsTER HIGcs, Executive Assistant C. B. NEBLETPE, Technical Assistant CHEMISTRY: G. S. FRAPS, Ph. D., Chief; State Chemist J. F. FUDGE, Ph. D., Chemist S. E. AsEURY, M. S., Assistant Chemist E. C. CARLYLE, B. S., Chemist WALDo H. WALKER, Assistant Chemist VELMA GRAHAM, Assistant Chemist T. L. OGIER, B. S., Assistant Chemist ATRAN J. STERGES, B. S., Assistant Chemist JEANNE M. FUEGAS, Assistant Chemist RAY TREIcnLER, M. S., Assistant Chemist J. K. FARMER. M. A., Assistant Chemist RALPH L. SCHWARTZ, B. S,. Assistant Chemist HORTICULTURE: HAMILTON P TRAUE, Ph. D., Chief RANGE ANIMAL HUSBANDRY: I. M. J0NEs, A M., Chief: Sheep and Goat Investigations J. L. LUSH, Ph. D., Animal Husbandman. Breeding Investigations STANLEY P. DAvIs, Wool Grader ENTOMOLOGY: F. L. THOMAS, Ph. D., Chief; State Entomologist H. J. REINHARD, B. S., Entomologist R. K. FLETCHER, Ph. D., Entomologist W. L. OWEN, JR., M. S., Entomologist FRANK M. HULL, M. S., Entomologist J. C. GAINEs, JR., M. S., Entomologist C. J. ToDD, B. S., Entomologist F. F. BIBBY, B. S., Entomologist CEcIL E. HEARD, B. S., Chief Foulbrood Ins ector OTTo AcKENsEN, Foulbrood Inspector AGRONOMY: E. B. REYNoLDs, Ph. D., Chief R. E. KARPER, M. S., Agronomist; Grain Sorghum Research _ _ IVIANGELSDOBF, Sc. D., Aqronomist; intcharge of Corn and Small Grain Investi- a ions D. . KILLOUGR, M. S., Agronomist; Cotton Breeding H. E. REA, . S., Agronomist; Cotton Root Rot Investigations W. E. FLINT, B. S., Agronomist _ B. C. LANGLEY, B. S., Assistant in Soils PUBLICATIONS: A. D. JAcKsoN, Chief VETERINARY SCIENCE: *M. FRANcIs, D. V. M., Chief H. SCHMIDT, D. V. M., Veterinarian F. E. CARROLL, D. V. M., Veterinarian PLIANT PATHOLOGY AND PHYSIOLOGY: . J. TAUBENHAUS, Ph. D., Chi W. N. EzEKIEL, Ph. D., Plant Pathologist and y Laboratory Technician W. J. BACH, M. S., Plant Pathologist B. F. DANA, M. S., Plant Pathologist FARM AND RANCH ECONOMICS: L. P. GABBARD, M. S., Chief W. E. PAULsoN, Ph. D., Marketim, Research Specialist C. A. BoNNEN, M. S., Farm Management Research Specialist ~ V. L. CoRY, M. S., Grazing Research Boiamst J. F CRIswELL, B. S., Assistant; Farm Records and Accounts "U. N. TATE, B. S., Assistant: Ranch Records and Accounts RURAL HOME RESEARCH: JEssIE WmTAcRE, Ph. D., Chief MARY ANNA GRIMEs, M. S., T617116 and Clothing Specialist EMMA E. SUMNER, M. S., Nutrition Specialist V l; SOIL SURVEY: "W T. CARTER, B. S., flhie < E. H. TEMPLIN, B. S., Soi Surveyor T. C. REITCH, B. S., Soil Surveyor L. G. RAasDALE, B. S., Soil Surveyor BOTANY: —-——-—————, Chief SIMON E. WOLFF, M. S., Botanist SWINE HUSBANDRY: _ FRED HALE, M. S., Chief DAIRY HUSBANDRY: O. C. COPELAND, M. S., Dairy Husbandman POULTRY HUSBANDRY: R. M. SHERWOOD, M. S., hief "**AGRICULTURAL ENGINEERING: MAIN STATION FARM: G. T. McNEss, Superintendent APICULTURE (San Antonio): H. B. PARKs, B. S., Chief A. . , B. S., Queen Breeder FEED CONTROL SERVICE: F. D. FULLER, M. S., Chief S. D. PEARCE, Secretary J. H. RocERs, Feed Inspector W. H. WooD, Feed Inspector K. L. KIRKLAND, B. S., Feed Inspector W. D. NORTHCUTT, JR., B. S., Feed Inspector SIDNEY D. REYNOLDS, JR., Feed Inspector P. A. Mo0RE, Feed Inspector SUBSTATIONS No. 1, Beevllle, Bee County: R. A. HALL, B. S., Superintendent No. 2, Troup, Smith County: t P. R. JoirNsoN, M. S., Act. Superintendent No. 3, Angleton, Brazoria County: R. H. STANsEL, M. S., Superintendent No. 4, Beaumont, Jelferson County: 1*" R. H. WYCHE, B. S., Superintendent No. 5, Temple, Bell County: HENRY DUNLAvY, M. S., Superintendent B. F. DANA, M. S., Plant Pathologist H. E. REA, B. S., Agronomist; Cotton Root Rot Investigations SIMON E. WoLFF, M. S., Botanist; Cotton Root Rot Investigations No. 6, Denton, Denton County: P. B. DUNKLE, B. S., Superintendent No. 7, Spur, Dickens County: _ R. E. DIcKsoN, B. S., Superintendent W. E. FLINT, B. S., Agronomist No. 8, Lubbock, Lubbock County: D. L. JoNEs, Superintendent FRANK GAINEs, Irrigationist and Forest Nurseryman No. 9, Balmorhea, Reeves County: J. J. BAYLEs, B. S., Superintendent No. 10, Feeding and Breeding Station, near Colle e Station, Brazos County: R. M. HERWOOD, M. S., Animal Husband man in Charge of Farm_ L. J . McCALL, Farm Superintendent No. ll, Nacogdoches, Nacogdoches County: H. F. MoRRIs, M. S., Superintendent "No. l2, Chillicothe, Hardeman County: J. R. QUINBY, B. S., Superintendent "J. C. STEPHENS, M. A., Assistant Agronomlst No. 14, Sonora, Sutton-Edwards Counties: W. H. DAMERON, B. S., Superintendent E. A. TUNNICLIFP, D. V. ., M. S., Veterinarian V. L. CoRY, M. S., Grazin Research Botantst "O. G. BAacocK, B. S., Col aborating Entomologist O. L. CARPENTER, Shepherd No. l5, Weslaco, Hidalgo County: W. H. FRIEND, B. S., Superintendent _ SHERMAN W. CLARK, B. S., Entomologist W. J. BACH, M. S., Plant Pathologist No. 16, Iowa Park, Wichita County: E. J. WILsoN, B. S., Superintendent Teachers in the School of Agriculture Carrying Cooperative Projects on the Station: O . W. BILsING, Ph. D., Professor of Entomology ‘<93 . W. ADRIANcE, M. S., Associate Professor of Horticulture P. LEE, Ph. D., Professor of Marketing and Finance . ScoATEs, A. E., Professor of Agricultural Engineering _ _ SMITH, M. S., Associate Professor of Agricultural Engineering Ph. D., Professor of Animal Husbandry . . MAcKEY, M. S., Associate Professor of Animal Husbandry . . IVIOGFORD, M. S., Associate Pro essor o Agronomy m~>p;U § F E s» 1A: of October 1, 1929. . S. JAuIsoN, M. S., Associate Pro essor o Horticulture ' ‘Dean, School of Veterinary Medicine. ** In cooperation with U. S. Department of Agriculture. ***In cooperation with the School of Agriculture. This Bulletin is a result 0f the studies 0f some chemical prob- lems connected with the investigations of cotton root rot being made by the Division of Plant Pathology and Physiology. Lab- oratory methods were needed for estimating the amounts of acid or sulphur required to bring experimental soils approxi- mately to a desired degree of acidity. Information was needed regarding the amounts of acid or sulphur required to make acid various kinds of soil. This Bulletin discusses the basicity of Texas soils, and the amounts of acid or sulphur required to make them acid. It contains a map showing the location of regions of soils of different degrees of basicity, together with a discussion of methods and other details. Basicity is related to soil fertility, soil acidity, possible needs of the soil for lime, and the effects of certain fertilizers, as well as to root rot. CONTENTS PAGE Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ‘ Buffer capacity of soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Method of estimating buffer capacity for acids . . . . . . . . . . . . . . . . . . 8 Relation of buffer capacity to other properties . . . . . . . . . . . . . . . . . .. 9 Effect of time on buffer capacity . . . . .._ . . . . . . . . . . . . . . . . . . . . . . . . 12 Relation of buffer capacity to the amount of sulphur required to change the acidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _. . . . . . 13 Basicity of Texas soils . . . . . . . . . . - - . . . . . . . . . . . . . . . . . . . . . . . . . .. 15 Method for soils of low basicity . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Relation of basicity to bufier capacity . . . . . . . . . . . . . . . . . . . . . . . .. 1'7 Basicity and buffer capacity of soil regions in Texas . . . . . . . . . . .. '. 17 Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19 BULLETIN NO. 400 DECEMBER, 1929 THE BASICITY OF TEXAS SOILS By G. S. Fraps and E. C. Carlyle When the cotton root rot investigations of the Division of Plant Pa- thology and Physiology showed that root rot is less prevalent on acid soils than 0n neutral 0r 0n basic soils (Bulletin 389), a number of chem- ical problems resulted. It became desirable to have a laboratory method for estimating the amount of acid required to bring a soil to a desired degree of acidity. It Was necessary to consider the practicability of mak- ing the soil acid as a control measure; to know how much acid is re- quired to make acid various soil types or soils in various regions, or to know how much sulphur should be used in case advantage was taken of the biological oxidation of sulphur to sulphuric acid. It Was desired to know the approximate basicity of soil types in various areas in Texas, to furnish a basis for ascertaining if there was any relation between them and the occurrence of cotton root rot. This Bulletin is a result of chemi- cal studies intended to furnish some of the desired information. The material is, however, of interest in other connections. . The degree of basicity or acidity of the soil is one of its most impor- tant characteristics. Soils with a high basicity are limestone soils. Lime- stone soils are generally fertile and durable. Soils with a moderate de- gree of basicity contain some lime and are neutral or nearly so. Soils with a low degree of bascity have a tendency to become acid. Highly acid soils, While favorable to a few crops, are generally unfavorable to most cultivated crops, especially legumes. Soils which have a high de- gree of acidity are usually treated with lime, especially when alfalfa, clover, and other legumes are to be grown. The basicity or acidity of soils may be related to the occurrence and destructiveness of cotton root rot or other plant diseases in various sec- tions of the State. The basicity is also related to the effect of fertilizer on the reaction of soils. Some fertilizer materials, such as sulphate of ammonia, have a tendency to cause the soil to become acid. Sulphate of ammonia reacts with the replaceable bases in the soil silicates; the ammonia replaces lime or magnesia (chiefly lime), producing sulphate of lime or magnesia, and silicates which contain ammonia. The ammonia may be used as such by plants, leaving hydrogen in its place, thereby producing an acid silicate. If bases are available, this acid silicate is neutralized. Part of the ammonia is oxidized to nitric acid before it is taken up by plants, and this also requires bases to neutralize it. The net result is that sulphate of ammonia and similar salts tend to make the soil acid. Whether or not the soil becomes acid depends on the amount of sulphate of ammonia used and on the power of the soil to neutralize the 6 BULLETIN NO. 400, TEXAS AGRICULTURAL EXPERIMENT STATION acidity. Acid soils are usually not so Well suited to the growth of culti- if ’ Vated crops, especially legumes, as neutral or slightly alkaline soils. Some other fertilizer materials, such as nitrate of soda, tend t0 make ‘ the soil basic. The sodium of nitrate of soda reacts with the replaceable lime or magnesia in silicates in the soil, producing calcium or magne- 1 sium nitrates, with sodium in place of part of the lime or magnesia in f.’ the silicates. When the nitrogen is taken up by plants, it leaves part of the calcium or magnesium as carbonates, which are basic substances. Texas Agricultural Experiment Station Ayala-u a Hedonism] cag- a n“. CCU-i: STATION. TEXAS BASICITY Or Sou. AREAS I\I_A_ - - . ¢ .- NOTMAPPED Map showing the predominant character of upland soils, as regards basicity. Figure 1. Here the use of nitrate of soda may tend to make an alkaline soil still more alkaline. The complex sodium silicates produced are liable to be highly colloidal and to cause the soil to run together and to have other undesirable ‘characteristics. Whether this will occur depends on the character of the soil and other circumstances. soda on acid soils tends to reduce the acidity. A mixture of nitrate of soda and sulphate of ammonia in proper proportions Will not affect th acidity of the soil. _ l The use of nitrate of ' ‘ii tr THE BASICITY OF TEXAS SOILS 7 The importance of these characteristics of sulphate of ammonia and nitrate of soda depends upon various conditions, and a discussion of this matter is outside the scope of this Bulletin. BUFFER CAPACITY OF SOILS The bufier capacity of a soil is closely related to the basicity. It is measured by the amount of acid or alkali required to change the inten- sity of the acidity or alkalinity to a desired extent. The intensity of acidity or alkalinity is measured by the hydrogen ion concentration, ex- pressed by pH. ~ _ When a soil is treated with an acid, the bases in the soil use up part or all of the acid. At first the soil may not become acid, but further addi- tions of acid will produce acidity or increase the intensity of the acidity if the soil is already acid. The amount of acid required to bring the soil to a given intensity of acidity (pH) depends upon the character of the soil, and may be termed the “buflier capacity for acid.” A soil with a pH of 7.0 is neutral; below 7.0 it is acid; and above 7.0 it is alkaline. The pH is a logarithmic function, so that the arithmetical value of the intensity of the reaction increases rapidly; taking pH 7.0 as 1, the rela- tive acidity is 10 for pH 6, 100 for pH 5, 1000 for pH 4, 10,000 for pH 3, while the relative alkalinity is 10 for pH 8, 100 for pH 9, 1000 for pH 10, and 10,000 for pH 11. Oharltin, according to Pierre, designates the total buffer capacity of soils toward acid as the number of cubic centimeters of normal sulphuric acid necessary to bring 100 grams of soil to a pH of 4.5, and he calls the total buffer capacity towards base the number of cubic centimeters of normal barium hydroxide necessary to bring 100 grams of soil to a pH of 9.5. The bufier capacity per 1.0 pH he defines, for acid, as the total buffer capacity to acid divided iby the original pH of the soil less 4.5 ; and for base the total buffer capacity to base divided by 9.5 less the original pH of the soil. Pierre uses similar definitions, but calls the buffer capacity per 1.0 pH the specific bufier capacity. [J our. American Soc. Agron. 19 (1927), 332.] ’ One cubic centimeter normal sulphuric acid to 100 grams of soil is equal to 490 parts per million of sulphuric acid added to the soil or 160 parts per million of sulphur or 500 parts per million of calcium car- bonate. The work reported in this Bulletin is chiefly in terms of parts per million of sulphur (in sulphuric acid) required by the soil to produce the desired pH. This method of reporting the results was adopted for the reason that the use of sulphur (as such) to change the reaction of the soil was under consideration, and the analyses were desired in terms of the material studied. It also seems to the writers that expression of the results in terms of some definite chemical substance, in parts per million of the soil, is more desirable than in terms of volume of acid of a certain strength to a certain quantity of soil. The latter form of ex- 8 BULLETIN NO. 400, TEXAS AGRICULTURAL EXPERIMENT STATION pression requires the use of three arbitrary terms not necessarily related, and seems complicated from a mental standpoint. The statement of buffer capacity as parts per million of sulphur required by the soil, or calcium carbonate in the soil equivalent t0 the buffer capacity, or in some similar way, seems more logical and perhaps easier t0 understand. METHOD OF ESTIMATION OF THE BUFFER CAPACITY FOR ACIDS After some preliminary work, the method described below was adopted to test the large number of soils to be used. The method provides for testing a large number of samples with various amounts of acid on suc- _ ceeding days, each treatment depending upon the previous one, until the desired figures are attained. Checks are made at the final points. As most of the soils selected were low in buffer capacity, the beginning point was acid equivalent to 200 parts per million of sulphur in the soil. Methfld! Weigh 8 grams of the soil into a 150 cc. beaker and add 10 cc. of .01N sulphuric acid. Allow to stand for 24 hours and add 90 cc. of water. Allow to stand till clear and determine pH. If the pH is more than 4.7 or less than 4.3, run pH according to Table 1. When there is a dash in the table, discontinue. In each case, after the soil has been in contact with acid for 24 hours, add water to bring the total a volume to 100 cc. and determine pH. The first column in Table 1 is pH acid to run; the second column is amount of acid to add to 8 grams of soil. Table 1.—Acid to use in treating soils for buffer capacity. v Parts per million If pH is over If pH is under sulphur in soil Quantity of acid to use for 8 grams 4.7 make 4.3 make equivalent to acid ' of soil test for test for use 50 . . . . . . . . . . .. 2.5 c.c. .01 acid +2.5c.c.wavter.... . . . . . . . . . . . . . . . . . . . . . . . . . . .. 100 . . . . . . . . . . .. 5.0 c.c. acid + 5.0 c.c. water . . . . . . . . . . . . . . . . . . . . .. 50 200 . . . . . . . . . . .. 10.0 c.c. .0_1 N . . . . . . . . . . . . . . . . . . . .. 500 . 100 300 . . . . . . . . . . .. 15.0 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 400 . . . . . . . . . . . . 20.0 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 500 . . . . . . . . . . . . 25.0 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . 1000 400 600 . . . . . . . . . . . . 30.0 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700 . . . . . . . . . . . . 35.0 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 800 . . . . . . . . . . . . 40.0 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . 900 700 00 . . . . . . . . . . . . 45 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1000 . . . . . . . . . . . . 50 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . 2000 800 1200 . . . . . . . . . . . . 60 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1500 . . . . . . . . . . . . '75 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . 1800 1200 1800 . . . . . . . . . . . . 90 c.c. acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2000 . . . . . . . . . . . . 100 c.c. acid. . . .; . . . . . . . . . . . . . . . . . . 4000 1500 2500 . . . . . . . . . . .. 1 .5 c.c.0.1Nacid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3000 . . . . . . . . . . . . 15.0 c.c. 0.1 N acid . . . . . . . . . . . . . . . . . 3500 2500 3500 . . . . . . . . . . .. 17.5 c.c. 0.1 N acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4000 . . . . . . . . . . . . 20.0 c.c. 0.1 N acid . . . . . . . . . . . . . . . . . 10000 3000 . . . . . . . . . . .. 25.0c.c.0.1Nacid................. 10000 . . . . . . . . . . . . 50.0 c.c. 0.1 N acid . . . . . . . . . . . . . . . . . 50000 5000 20000 . . . . . . . . . . . . 100 0 c.c. 0.1 N acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50000 . . . . . . . . . . . . 25 0 c.c. 1.0 N acid . . . . . . . . . . . . . . . . . 100000 20000 100000 . . . . . . . . . . . . 50.0 c.c. 1.0 N acid . . . . . . . . . . . . . . . . . 200000 . . . . . . . . . . . . . . 200000 . . . . . . . . . . .. 100.0 c.c. 1.0 N ac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . fl/r THE BASICITY OF TEXAS SOILS 9 RELATIONS OF THE BUFFER CAPACITY TO OTHER PROPERTIES The analyses of a number of Texas soils were averaged in groups ac- cording to their buffer capacity (Table 2). The analyses include the amounts of 0.02N sulphuric acid neutralized by the soils expressed as calcium carbonate, termed basicity .02N ; the amounts of 0.2N acid neu- tralized by the soil, termed basicity 0.2N; and the lime and magnesia soluble in strong hydrochloric acid (Hilgard’s method). The methods used for 0.2N basicity and .02N basicity are described in another part of this Bulletin. It is seen from Table 2 that as the average buffer capacity increases, the basicity, the lime, and magnesia also increase. The increase is not regular, which is to be expected. The bases neutralized in the soil by .02N sulphuric acid or 0.2N nitric acid, are not entirely in forms suit- able to act as buffers to prevent the soil from becoming acid. Parts of these bases may be calcium carbonate or basic silicates, which may neutralize some acid writhout becoming acid, but part of these leave acid silicates When the base is extracted, and part of the bases come from silicates which are decomposed by the strong acid used. The pro- portions of these three groups vary in different soils, so that the pro- portions of lime or magnesia soluble in strong acid which can help keep the soil from becoming acid vary with different soils and can be ascer- tained only by direct tests. It is diflicult to compare the figures in Taible 2 on account of their be- ing expressed in different units. For this reason the buffer capacity, the basicity by .02N acid, the basicity by 0.2N acid, the lime and magnesia, and the sums of the lime and magnesia, were calculated to their equiva- lent in parts per million of calcium carbonate. The results are presented in Table 3. This table also contains the buffer capacity expressed as percentage of the basicity estimated by the two acid methods and of the lime plus magnesia calculated to calcium carbonate. An examination of Table 3 shows that the buffer capacity averages 24.3 to 92.4 per cent of the basicity measured by .()2N acid. A smaller percentage of the basicity determined by O.2N acid than by .O2N acid is available to act as a buffer (20.8 to 42 per cent) and a very much smaller percentage (6 to 23 per cent) of the lime and magnesia soluble in strong acids. In each case the percentage increases with the basicity of the soil. That is to say, as a rule, the more lime and magnesia present in the soil, the greater is the percentage which can be used to neutralize acids and act as a buffer to prevent the soil from becoming acid. These results mean that most of the lime and magnesia dissolved by strong acids from soils is p-resent as silicates, which do not have the power of neutralizing weak acids. 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Bow»: .63. v.v 25am 3E. v.v Hwamoz .3638 Sbsm 11 THE'BASICITY OF TEXAS SOILS 0.0 0 .m0 . . . . . . . . . . 00000 00wwm 0000w 0000m . . . . . . . . . 00m0 . . . . . . . . . . . . .000m|000m 0 0.0m 0. 00 0.m0 000mm 00000 000m0 00w00 0w00 0mww . . . . . . . . . . . . 600N080 0 w.0 0.0m 0.00 00mm0 00000 0000w 000mm 0m00 00m0 . . . . . . . . . . .. 000mI0000 0 0.0m 0.0m 0.00 000wm 00000 00000 00000 0000 0000 . . . . . . . . . . . . 00000000 0 m.00 0.0m 0.w0 000wm 00000 00wm0 000w0 00ww 0000 . . . . . . . . . . . . 0000|00m0 mm 0.00 0mm 0 . 00 00wmm 000m0 00000 00000 0000 0000 . . . . . . . . . . . . .00m0I0000 00 0. m0 0 . mm 0 . m0 00mmm 0w000 000m0 00000 000w 0m00 . . . . . . . . . . . . .0000I000 mm 0.m0 m.wm 0.m0 00w0m 0000 0w0m0 00m00 0000 000m . . . . . . . . . . . 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Zm0. 00350.05 mcUmU mm nOUmU 50525 00000.50 00000000 0:00.03 .8052 03.0.3054 0o o0 5 0o R. 5 0o 00 5 05m @500 m0mvcwm0>0 ma @5010 m0 m0. 0w00-m co 0.350 0:050 5:05:70 00000000 09.00050 .5555 .50 3.00.0 5 @500 0o 0005000500 mm 0630093 @3358 H.500 05m 00022000 .:..05m01.m @5010. 12 BULLETIN NO. 400, TEXAS AGRICULTURAL EXPERIMENT STATION than the bases dissolved by 2N or stronger acid. The silicates of cal—- cium and magnesium are not so readily attacked by .02N acid as by 0.2N acid. There is a close relation between the buffer capacity for acid and basicity as measured by .02}? acid. The correlation coefficient is .79i—.02‘ for 164 soils. EFFECT OF TIME ON BUFFER CAPACITY The buffer capacity of soils for acids may become greater with the» lapse of time; that is, the soils treated with acid may become less acid with the process of time. T0 test this, soils with tested buffer capacity’ were allowed to remain in contact with acid. The results are given for" various periods of time in Tables 4 and 5. There is an appreciable Table 4.——Effect of time on pH of soils to which acid was added. Amount of acid ex- Laboratory pressed as sulphur in Regular pH after pH after pH after pH after No, parts per million method 2 days 4 days 6 days 8 days 6208 200 . . . . . . . . . . . . . . .. 4.1 4.5 4.6 4.6 4.7 7613 600 . . . . . . . . . . . . . . .. 4.3 4.7 4.9 5.0 5.0 12584 1800 . . . . . . . . . . . . . . .. 4.5 4.9 5.1 5.1 5.3 12520 300 . . . . . . . . . . . . . . .. 5.0 5.3 5.3 5.4 5.6 12674 700 . . . . . . . . . . . . . . .. 5.1 5.3 5.4 5.5 6.1 9376 300 . . . . . . . . . . . . . . .. 4.8 5.1 5.2 5.2 5.2 8340 400 . . . . . . . . . . . . . . .. 4.5 4.6 4.7 4.7 4.7 Average . . . . . . . .. 4.6 4.9 5.0 5.1 5.2 Table 5.—Effect of time on pH of soils to which acid has been added. Amount of acid ex- Laboratory pressed as sulphur in Regular After 30 After 60 After 5% After 0. parts per million method days days months one year 12588 600 . . . . . . . . . . . . . . .. 4.1 4.5 4.5 4.8 4.5 12676 300 . . . . . . . . . . . . . . .. 4.3 4.7 4.7 . . . . . . . . .. 4.6 12586 400 . . . . . . . . . . . . . . .. 3.9 4.1 4.2 5.3 4.3 18216 900 . . . . . . . . . . . . . . .. 2.9 4.1 4.1 4.2 4.2 9349 500 . . . . . . . . . . . . . . .. 3.7 5.0 5.1 5.1 5.3 9333 300 . . . . . . . . . . . . . . .. 4.3 4.4 4.5 4.5 5.1 12667 300 . . . . . . . . . . . . . . .. 6.6 6.4 6.0 5.3 4.9 697 700 . . . . . . . . . . . . . . .. 4.0 4.7 4.8 4.8 4.3 18911 700 . . . . . . . . . . . . . . .. 4.8 4.9 4.9 5.0 5.1 9378 600 . . . . . . . . . . . . . . .. 3.8 4.5 4.5 4.4 4.5 7708 800 . . . . . . . . . . . . . . .. 5.6 6.5 6.7 6.7 6.5 18539 200 . . . . . . . . . . . . . . .. 4.7 4.7 4.8 4.9 4.6 18207 500 . . . . . . . . . . . . . . .. 4.7 4.7 4.7 4.9 4.7 18211 600 . . . . . . . . . . . . . . .. 4.9 4.9 4.9 5.1 4.9 9376 500 . . . . . . . . . . . . . . .. 3.6 4.4 4.4 4.1 4.0 6268 300 . . . . . . . . . . . . . . .. 5.0 6.2 6.2 6.1 . . . . . . . . .. 18228 500 . . . . . . . . . . . . . . .. 4.4 4.6 4.6 4.6 4.5 18208 300 . . . . . . . . . . . . . . .. 4.0 4.1 4.1 4.2 4.4 18205 500 . . . . . . . . . . . . . . .. 4.3 4.7 4.6 4.6 4.3 17440 600 . . . . . . . . . . . . . . .. 4.1 4.9 4.8 4.3 4.2 18210 600 . . . . . . . . . . . . . . .. 5.1 5.9 5.8 6.7 6.0 18217 500 . . . . . . . . . . . . . . .. 4.8 4.6 4.6 4.6 4.7 932 300 . . . . . . . . . . . . . . .. 3.9 4.5 4.6 4.4 3.7 12590 500 . . . . . . . . . . . . . . .. 4.4 4.9 4.7 4.3 4.3 Average the above 24 soils. . . . 4.4 4.9 4.9 4.7 4.7 Average 23 soils (second set).. . 4.7 5.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average 23 soils (third set) . . . . 4.7 5.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average 20 soils (fourth set). . . 4.6 5.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - THEDBAsIGITfl-ofi _ , i 13 average decrease in acidity in two days as compared with 24 hours in the regular method used. This decrease continues up to about 6 days, varying with the soil. After that, While some few soils decrease in acidity in 5% months to one year, the usual change is in the limit of error and the average change is small. While the change in 6 days with some soils is small, with others it is large. It averages in 30 days, from 0.5 to 0.’? pH with the three sets of soils used in the work. The relation of the buffer capacity for acid as determined in about 24 hours to the buffer capacity of the soil after sev- eral weeks is therefore irregular, and it is not possible to state exactly the amount of the buffer capacity after 30 days from the estimation in 24 hours. In one set of 24 soils, the change in pH in 21 to 28 days was very small; pH averaged 5.3 for 21 days and 5.4 for 28 days. A contact of soil and acid for 24 hours is not long enough, though 6 days may be suflicient for most soils. RELATION OF BUFFER CAPACITY TO THE AMOUNT OF SULPHUR REQUIRED TO CHANGE THE ACIDITY When flowers of sulphur, ground sulphur, or some other form of free sulphur is placed in the soil, the sulphur is oxidized to sulphuric acid, and the soil will become acid if a sufficient quantity of sulphur is used. The change is chiefly a biological process brought about by bac- teria, which varies with the temperature, the activity of the organisms, and other conditions. For a review of this process, see Joffe, Bulletin 3'74, New Jersey Experiment Station. For the purpose of ascertaining the effect of sulphur on the acidity of soils and its relation to their buffer capacity, mixtures were made of soil, sulphur, and water and left at room temperature for various periods of time, water being added from time to time. Table 6 shows only the minimum amounts of sulphur which were required to bring the pH of the soils tested to about 4.5 in the time specified. A large number of other tests were included in the experi- ments. Considerable amounts of sulphur were needed to change the pH in the first 3O days; while the amounts of sulphur required increase with the amounts of acid used for this purpose in the laboratory test, the relations are not close. At the end of 60 days, the same acidity (pH) was secured with smaller amounts of sulphur, although they were considerably larger than the amounts of acid required. A still smaller amount of sulphur was required at the end of 90 days to produce the same degree of acidity. Soils with a buffer capacity of 200 for a. pH of 4.5 required approxi- mately 400 parts per million of sulphur to efiect a corresponding change in the pH of the soils in 120 days. A buffer capacity of 250 to 400 re- quired about 500 parts per million of sulphur; a buffer capacity of‘, 500 14 BULLETIN NO. 400, TEXAS AGRICULTURAL EXPERIMENT STATION w.w 82 w.w 8M: w .w ccwm w. w cccw w.w 8S w.w 82 hwwmfi w .w ccwm a .w cccw w . w ocow h . w cccw h . w o8; w. w 82 safl N . w cccw w . w cccw w . w ocow 7h cccw w . w o2 w .w 82 wwmh w.w 8S w.w 82 h.w ocow w.w cccw . . . . . . . . . . . . . . . . . . . . . . . . w.w 8S wohh w.w ccw w.w 8Q w.w cccw h.w ocow . . . . . . 4 . . . . . . . . . . . . . . . . . h.w ocw wwwmfi w.w ocow h.w ocow h.w ocow w.w cccw . . . . . . . . . . ... . . . . . . . . . .. w.w ocw SQ: h.w cccw w.w cccw _ .w ocow h.w ocow . . . . . . . . . . . . . . . . . . . . . . . . w.w cow Nhwh w.w cow h.w cwh w.w cowm 7w ocwm 7w ccw w.w och 2N2 w.w ccw h.w ocw c.w 2...: w.w ocow 7w ocw w.w och 2N2 w . w ccw w . w oofi w . w cccw w w cccw o . w ccw w . w ccw owwh w . w 82 w . w ocow w . w cccw w. w ocow o . w cch w . w ccw $5 w.w cwh 5w cwh w.w cwh w.w ocwm c.w ocw w.w ccw 2E. w.w ocw w.w 8Q 7w cccw w.w cccw . . . . . . . . . . . . . . . . . . . . . . . . w.w ocw Nwwh w . w 8S fi .w o9: h . w oocm w . w ocow o . w och w . w ccw whww w.w o2: w .w 82 w.w oowm H .w ocwm w . m ccwm w.w ocw >32 w.w cow w.w coo w.w 8Q w.w ocow . . . . . . . . . . . . . . . . . . . . . . .. w.w cow wwwc w.w ocw 7w ccw w.w cwh w.w ccwm . . . . . . . . . . . . . . . . . . . . . . . . 7w ccw Q34; w.w 82 7w 82 7w 2.2 w.w cccw . . . . . . . . . . . . . . . . . . . . . . . . 7w ccw wwwfl w.w cow w.w cow w.w 8§ 5w ocow 7w cow w.w cow :2: 7w ccw w.w cow 5w cow 5w cccw . . . . . . . . . . . . . . . . . . . . . . . . w.w ccw hmmh w . w ocw w .w cow h . w cwh o . w cowm w . w ocw m . w ccw Q3: 7w 82 w.w 82 c.w Q9: 5w 82 . . . . . . . . . . . . . . . . . . . . . . ..w.w cow 3Q: w.w ccw w.w 25 5w 2...: w.w 8Q w.w cow w.w cow 8E w .w ocw w.w ocw c.w cowm w. w oowm w.w cow w.w ccw Qqwfi m . w 82 w . w 82 w . w ocow o. w cccw m . w cow w . w ocw wwcw w . w 82 7w 82 w . w 2.2 w . w cccw w . w cow w. w ccw cwwo w .w cow w . w cow w . w 8Q w . w ocow w . w ocw w. w ocw whwm w.w cwh 5w cwh w.w 82 w.w ccwm . . . . . . . . . . . . . . . . . . . . . . . . c.w cow wmmfi h . w cow w. w cwh w . w 82 w. w oowm w . w cow w . w cow 8Q: w.w cow w .w cwh w.w 82 w . w cowm o . w cow w . w ocw wwwNH w . w cow w . w ocw w .w o9: w . w ocow m 4 w ocw h. w oww wwmw w . w cow h .w ccw w . w cwh w . w ccwm 7w cow w . w oww wwww w.w ccw w.w cwh w.w 82 w.w ccwm w.w cow 5w ocw awmfi o . w cow w. . w com w. w 82 a . w cccw w. w ccw c . w ccw 5mm w.w cow w.w ocw 5w cow w.w cowm w.w ocw w.w ccw whww w.w ccw w.w cow 7w ocw w.w cccw . . . . . . . . . . . . . . . . . . . . . . . . w.w ccw wSQ w.w ccw w.w ocw w.w ccw w.w oowm 7w cow w.w cow owwc w.w cwh 5w 82 w.w ocwm 5w cowm . . . . . . . . . . . . . . . ... . . . . .. 7w own mg: 7w ccw w .w cwh w.w cwh w .w ccwm w . w ocw w . w oww wwwo m. w ocw w.w ocw w.w ocw w.w oowm o. w cow w.w own wmwc w.w ocw w.w ccw 5w cwh 5w 82 . . . . . . . . . . . . . . . . . . . . . . .. 5w com owwww 7w ocw w . w ocw m . w cwh w . w cowm a . w ocw h . w com wwwfi w.w cwh 5w cwh w.w 82 w.w ooww . . . . . . . . . . . . . ...‘ . . . . . . ..w.w com 28 Ea 5:35 in psnfisw In 5.55am Ea .5535 . w.w Em c.5253» wcsoE/w HG5OE< £2554 In 30in wxv: Em w.w in pxwn .oZ hfiuwmmu homsm wwwumcmo hvtsm Eofifionwd 92% ofl 22% cc 5% ow was. ow Quad flow on» we zfiwwom nobomma “on n23»; 2:315 wan Bow we wowfimlaw was? THE BASICITY OF TEXAS SOILS 15 required about 700; a buffer capacity of 700 required‘ about 800; a ca- pacity of 800 to 1000 required about 1600 to 2400 parts per million of sulphur. These represent the approximate minimum quantities. There is considerable variation, and it does not appear possible to predict the exact amount of sulphur necessary to produce a desired degree of acidity. This renders difficult the proper use of sulphur to change the soil acidity to a point near the toxic limit of acidity, since if too much sulphur is used, the soil may become too acid, with consequent damage to the crops. The amount of sulphur required to secure the desired degree of acidity of the soil when the buffer capacity of the soil was over 800 parts per million of sulphur, was much higher in proportion than when the buffer capacity was lower. This may be due to accidental variations in the sulphur-oxidizing organisms in the soils studied, but it may also mean that sulphur-oxidizing organisms are less active in soils of high basicity than in those of low basicity or that the larger amounts of sulphur may delay the activity of the oxidizing organisms, or that reduction of sulphuric acid may occur. BASICITY OF TEXAS SOILS When a soil is brought in contact with an excess of acid, some of the lime, magnesia, and other bases of the soil go into solution and neutralize ' part of the acid. The amount of acid neutralized may readily be meas- ured by titrating the excess acid with a solution of a base. The amount of base which goes into solution depends on the kind of acid, the strength of the acid, the proportion of soil to acid, the time, temperature, and other conditions. . The basicity of Texas soils as measured by the methods here described was studied for the purpose of securing a method to make a quick preliminary grouping of soils with respect to probable buffer capacity. The basicity of a large number of samples had already been tested in the laboratory and could be used i.n the preliminary sorting of the soils, after their relations were ascertained. The term basicity is here used to mean the bases which neutralize dilute nitric acid, sulphuric acid or similar acids, as measured by titra- tion of the acid after contact with the soil. It is recognized that this does not correctly represent the real basicity of thesoil, as pointed out already in this Bulletin. A routine method is used in connection with the estimation of active phosphoric acid and active potash, in which one part soil is brought in contact with 10 parts of 0.2N nitric acid 5 hours at 40° C; a portion of the filtrate, after dilution and boiling to expel carbon dioxide, is titrated with 0.1N sodium hydroxide and phenol- phthalein. The results are expressed as acid consumed by the soil, in per- centage of the acid used, or as 0.2N basicity, in terms of calcium car- bonate equivalent to the acid consumed. An acid consumed of 10 per cent is equivalent to abasicity of 1.0 per cent of the soil; that is, the bases which neutralize the acid under the conditions of the test, would 16 BULLETIN NO. 400, TEXAS AGRICULTURAL EXPERIMENT STATION be equivalent to 1 per cent calcium carbonate in the soil. All the 0.2N acid is neutralized by some very basic soils, in Which case the exact basicity may be estimated by a subsequent digestion with normal acid, though in routine Work the results are frequently expressed as 10 per cent basicity. Method for Estimation of Basicity 0f Soils Low in Basicity The estimation of basicity or acid consumed described above is not highly accurate, though it is considered to be sufficiently accurate for the purpose for which it is used. It requires too long a period of time for the approximate estimation of basicity when made alone and is not sufficiently accurate for soils low in basicity. Accordingly, experiments Were made to devise, (a) a quick method for basicity, (b) a method for soils With 10W basicity. Qlli¢k Method f0!‘ Bflsidty! Sulphuric acid was used, for the reason that for the purpose of changing the soil reaction in root rot investi- gations, sulphuric acid Would be used, possibly as such but more probably formed in the soil by the bacterial oxidation of sulphur. Five grams of soil Were digested with 5O cc. of 0.2N sulphuric acid under the conditions V tested. The liquid Was filtered, and 10 cc. of the filtrate Was diluted With about 75 cc. of Water; it Was then boiled about a minute to expel carbon dioxide, and titrated With 0.2N sodium hydroxide. Four sets of twelve soils each were tested under various conditions and the average results are given in Table '7. Table 7.——Average effect of time and temperature on average basicity as measured by 0.2 N sulphuric acid, expressed as carbonate of lime. Set 1 Set 2 Set 3 Set 4 % % % % Room temperature: 10 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.21 1.53 1.34 1.17 30 minutes, 40° C . . . . . . . . . . . . . . . . . . . . . . 1.24 1.58 1.38 1.20 6O minutes, 40° C . . . . . . . . . . . . . . . . . . . . . . 1.23 1.58 1.42 1 .55 2hours, 40°C . . . . . . . . . . . . . . . . . . . . . . . .. 1.31 1.63 1.52 1.31 Usual method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.47 1.48 1.37 41 Number of samples . . . . . . . . . . . . . . . . . . . _ . . . . 13 12 12 1 There are differences between the average results secured by the four methods, the shorter method giving the lowest results. The results are comparative and not absolute. The use of ten minutes With, shaking at room temperature appeared suitable and was adopted. The results are reported as acid consumed (10 minutes) or 0.2 basicity (10 minutes) to distinguish it from the other method. Mef-hfld f0!‘ SOUS LOW ill Basicityi The following method was tested. Treat 10 grams of soil with 100 cc. of 0.02N sulphuric acid for the time and ‘at the temperature specified. Filter, heat 50 cc. to boiling for one minute, and titrate with 0.04N sodium hydroxide and phenolphthalein. THE BASICITY OF‘ TEXAS SOILS l7 One cc. 0.02N acid equals .02 per cent basicity expressed as calcium car- bonate. Report as .02N basicity. Basicity by the above method was determined in 36 soils by three difiterent methods; (A) 24 hours at room temperature, (B) one hour at room temperature, and (C) 15 minutes with shaking. The average results are given in Table 8. The results vary somewhat with the method of treatment, the 5 hours at 40° giving the highest results, and one hour at room temperature the lowest. Shaking 15 minutes at room temperature gives higher results than one hour without shaking. Table 8.—Average effect of time and shaking on basicity measured by 0.02N sulphuric acid Basicity % A-24 hours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .341 B-1 hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .236 C-15 minutes shaking . . . . . . ._ . . . . . . . . . . . . . . . . . . . . . .284 D-Basicity by 0.2 N sulphuric acid 5 hours at 40° C. . .430 Average difference A-B . . . . . . . . . . . . . . ." . . . . . . .105 Average difference C-B . . . . . . . . . . . . . . . . . . . . . .048 Number of samples . . . . . . . . . . . . . . . . . . . . . . . . 360 RELATION OF BASICITY TO BUFFER CAPACITY The analyses of a number of soils grouped according to basicity as ‘measured by 0.2N acid were averaged, and the results are given inmTable 9. Soils with a .basicity of 0 to 0.5 per cent have a buffer capacity for pH 4.5 of 100 to 1000 parts per million of sulphur in the soil, With an average of 309. Soils with a basicity of 0.51 to 1.0 per cent have an average capacity of 669 parts per million of sulphur, varying from 100 to 1500 parts per million. These two groups also contain acid soils. the pH of the soil varying from 4.3 to 7.4 with an average of about 6.5. The amounts of acid or sulphur required to change the pH of many soils in these two groups are within the limits of practicability. The buffer capacity (expressed as sulphur) of soils with a basicity of 1 to 2 per cent varies from 200 to 5000 parts per million, with an average of 1746. The amounts of sulphur or acid required to change the acidity ‘of these soils are mostly too high to be oi’. practical significance. The pH of these soils did not fall below 5.5, and therefore probably none of these soils were acid enough to cause damage. Soils with a basicity of more than 2.0 per cent are neutral or slightly alkaline in reaction, and require large amounts of sulphur or acid to make them acid. ' BASICITY AND BUFFER CAPACITY OF SOIL REGIONS IN TEXAS The basicity of a large number of Texas soils has been determined by ’0.2N acid. By means of these analyses, the Soil Survey reports, and "the regional soil map prepared by W. T. Carter, of the Soil Survey, a map has 18 BULLETIN NO. 400, TEXAS AGRICULTURAL EXPERIMENT STATION nv mm mw omfi Q2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . .. . 1.26m Mo hfiEsz ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..QWN.~Q>N.ZOw _NG@NT~Q%O IQ mw $.R.I~&..@ ¢.&.-|Am..@ %.§|%.v.¢ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .WUEQHHKQ iwom .»N:@w@k° %Q Qfl.@ . M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - . QQQO hUQ QN@WUQWNE ®@@H;Qw|@@nv< - . @ @m. ‘w . . fi§~ . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v .Hgmvnv hUQ -UE.: Q§Q~.;ow|@wmv< . . . . . . . . _ mw. fiw. mm. mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 5m fiufiswcoo Bum mo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...®m.N-®>N k0.“ hOQ %..ZOGQGO Hflxim Q . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . 4 . . . . . . . . .QWN.~Q>.N HQ% HQQ WHflvWQNO HO¢5m @262 83m O95. 82 82 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6:656 m. a IQ 5 55:8 8Q 363.8 swim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . nmt¢ hc% HUQ %P@UNQ.NU hflbgm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .U@N¢~Q>.W Amv.¢ HQ% hUQ %H@ONQNO hQtfi-m m-w M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HQQO MOQ .08: %O QMGHOQQGQ wfi .%.ZO@WGQ UMNAQ>< 9m .$>o Qalqw o.N|o.~ 9TB. mro hfioimm fizommwm xfimowmmm >fioimm >fi2wmm~ Simian 3 mnmukooom £38m E wwwfisé mmow mo wmwimcw owmhriwlaw 03mm. THE BASICITY OF TEXAS SOILS 19 been prepared showing the prevailing basicity of the surface of the up- land soils in various sections of Texas (see Figure 1). There are decided variations in the cahracteristics of the soils in all sections, and there are soils which vary widely from the basicity of the area as shown in the map. The map merely gives a generalized idea of the basicity of the soils in the various areas, and the fact that local variations occur must not be forgotten. The map also corresponds to the upland soils. As a general rule, alluvial soils in Texas are more basic than upland soils. Soils With 10W bflsicityi The soils with a basicity of less than 1 per cent occur chiefly in the East Texas timber country, the East Texas flat- Woods section, the West Cross Timbers, and the soils of the High Plains or Staked Plains. There are also areas in Brooks, Willacy, Mason, and Llano counties. As has already been pointed out (see Table 9) these soils have a buffer capacity of 100 to 1000 parts per million of sulphur. They have a lower lime and magnesia content than the other soils. Some of these soils are acid. The acid soils occur in the East Texas timber country or flat Woods section. Acid soils which need lime for legumes are likely to be found in this section. Some few soils may be made acid by con- tinuous use of sulphate of ammonia in fertilizers. It might be practicable to make some of these soils acid by the use of sulphur, if such practice is a found advisable to control cotton root rot. Soils with High Basidtyi The highly-basic calcareous soils occur chiefly in the Black Waxy Prairie Belt, though there are also areas around McMullen and Bee counties. These soils tend to be slightly alka- line in reaction. They have a high buffer capacity. These soils are not likely to become acid, or to need lime for legumes. The amount of sul- phur required to make them acid would be entirely too large to be practical. Soils With Mflderate Basicityi The soils of a large portion of the State have a basicity of 1 to 2 per cent‘. These soils are basic, have a moderate buffer capacity, and are neutral in reaction. They generally contain enough lime for legumes and have so high a buffer capacity that the use of sulphur to change the pH to be acid would be impractical. SUMMARY AND CONCLUSIONS 1. The basicity and acidity of the soil are closely related to their agricultural value. Basic soils are generally better suited to the growth of agricultural crops than acid soils. 2. The basicity of the soil as the term is here used is measured by the amount of acid neutralized by the soil expressed as carbonate of lime. The methods for basicity are described and studied. ~. 2O 10.. BULLETIN NO. 400, TEXAS AGRICULTURAL EXPERIMENT STATION The bufier capacity as here described is the amount of acid re- quired to change the intensity of the acidity to a desired extent. The buffer capacity for bases as here discussed is expressed as quired to change the soil to a pH of about 4.6. The methods are described. - The buffer capacity averages from 24 to 92 per cent of the basicity measured by .02N acid and a smaller percentage, 21 to 42 per cent of the basicity, measured by .2N acid. Only fromB to 23 per cent of the lime and magnesia soluble in strong acid acts as buffer under the conditions here discussed. In each case the percentage available for buffer action increases with the basicity of the soil. ' A large proportion of the lime and magnesia dissolved by strong acid. from soils is present as silicates which do not have the power of neutralizing weak acids. The buffer capacity is larger if the acid is allowed to remain in contact with the soil 6 to 8 days than in 24 hours, the routine method. p Elemental sulphur is oxidized in the soil to sulphuric acid, which consumes the bases of the soil. At room temperature, the change occurs somewhat slowly. It is difficult to estimate exactly the amount of elemental sulphur required to produce a desired change in the acidity of the soil. . Soils with a buifer capacity of 200 for a pH of 4.5 require ap- proximately 400 parts per million of sulphur to effect in 120 days, the corresponding change in the pH of the soils tested. A buifer capacity of 250 to 4:00 requires about 500 parts per million of sulphur; a buffer capacity of 700 requires about 800; a buffer capacity of 800 t0 1000 requires about 1600 to 2400 parts per million of sulphur to effect a similar change in 120 days. There is an approximate relation between the basicity and buifer capacity for acid. Soils with a basicity of 0.5 per cent have a buffer capacity, for the pH of 4.5, of 100 to 1000 parts per million of sulphur in the soil, with an average of 309. Soils with a basicity of .51 to 1.0 per cent have an average buffer capacity of 669 parts per million of sulphur. Those with a basicity of 1 to 2 per cent have an average buffer capacity of 1746 and a higher basicity brings a corresponding high buffer capacity. A map is given showing the occurrence of soils of different degrees of basicity of the surface soil. ~ 37o5r2 .1 f . . . , we ... l»; ».~.~...r_>r_e'-.¢z h: parts per million of sulphur in the form of sulphuric acid re?‘