It is generally conceded now that microorganisms play a large part in the transformations through which various plant food constituents pass, in the soil. They are the agents which are chiefly responsible for the production of available plant food. They break down organic matter, liberating the plant food constituents contained therein. The products of this decomposition react with the complex mineral soil constituents and change them into soluble, available compounds. Certain microorganisms also have the ability of utilizing the free nitrogen of the atmosphere, fixing it in the soil, to serve later for the feeding of plants

Brown, P. E.

Tomlin, B. A.

English

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 36 Annual Issue Article 11 1929 The Effect of Various Treatments on Microorganisms in the Soil under a Five-Year Rotation P. E. Brown Iowa State College B. A. Tomlin Iowa State College Copyright ©1929 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Brown, P. E. and Tomlin, B. A. (1929) "The Effect of Various Treatments on Microorganisms in the Soil under a Five-Year Rotation," Proceedings of the Iowa Academy of Science, 36(1), 79-85. Available at: https://scholarworks.uni.edu/pias/vol36/iss1/11 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. THE EFFECT OF VARIO US TREATMENTS ON MICRO-. ORGANISMS IN THE SOIL UNDER A FIVE-YEAR ROTATION P. E. BROWN AND B. A. TOMLIN It is generally conceded now that microorganisms play a large part in the transformations through which various plant food constituents pass, in ·the soil. They are the agents which are chiefly responsible for the production of available plant food. They break down organic matter, liberating the plant food constituents con-tained therein. The products of this decomposition react with ~he complex mineral soil constituents and change them into soluble, available compounds. Certain microorganisms also have the ability of utilizing the free nitrogen of the atmosphere, fixing it in the soil, to serve later for the feeding of plants. Among the various functions of bacteria in the soil, then, the production of available plant food and the fixation of atmospheric nitrogen may be listed as the most important. Because of these activities of soil organisms and because of other functions which special groups exert under special conditions, there is quite evidently a rather definite relationship existing between bacterial activities in soil and their crop-producing power. Many attempts have been made to show the existence of such a rela-tionship and in a number of instances, the results have been quite conclusive. It has come to be believed, therefore, that any soil treatments which would h;:tve a beneficial effect on crop yields .must necessarily have a similar stimulative influence on the devel-opment of bacteria and especially on certain important bacterial activities. In fact it seems probable that the effects of various treat-ments of soils on bacterial action may serve to indicate the crop effects which may be expected. With these things in mind, many investigators have studied the influence of a wide variety of treatments on the soil flora and on the activities of the better-known groups of soil organisms. The literature along this line is rather extensive and no attempt will be made to review it here. Very excellent reviews of the work with manure, lime and phosphate fertilizers have been given in a num-79 1Brown and Tomlin: The Effect of Various Treatments on Microorganisms in the Soil unPublished by UNI ScholarWorks, 192980 IOWA ACADEMY OF SCIENCE ber of publications by Waksman 1 2 , Brown 3 4, Greaves and Car-ter 5 and others. The experiments reported in this paper were planned to throw further light on the problem of the influence of certain field treat-ments of soils on biological activities. The work was carried out on the soils from a series of plots at the Agronomy Farm of the Iowa Agricultural Experiment Station. The soil is typical of the Wisconsin drift soil area and a mapping on a scale of one inch per one hundred feet shows the plots on the livestock end of the series (plots 924-928) to be mostly on Car-rington loam or a fine sandy loam variation while the plots at the other end of the series are on Webster silty clay loam or loam. Thus absolute comparisons cannot be made throughout the series but for each group of plots the soils may be compared quite accu-rately. The plots are one-tenth of an acre in size and have been under treatment for 13 years. A five-year rotation of corn, oats, clover, wheat .and alfalfa is followed, the alfalfa remaining on the land for five years. The series was in corn when these tests were begun in the fall of 1926. The treatments employed were as follows : PLO'.!' No. 924 926 927 928 929 931 932 933 Check (Ko treatment) Manure+ Limestone :Yianure +Limestone+ Rock Phosphate Manure+ Limestone+ Superphosphate Check Crop Residues + Limestone Crop Residues + Limestone+ Rock Phosphate Crop Residues+ Limestone+ Superphosphate Manure is applied to these soils at the r.ate of 10 tons per acre per five-year rotation. Rock phosphate is added .at the rate of 2500 pounds per acre each five-year period and superphosphate is em-ployed at the rate of 200 pounds per acre annually. Limestone is supplied in sufficient amounts to neutralize the acidity of the soil as determined by the Truog qualitative test. The crop residues treatment consists in the return to the land of the stover and straw and the plowing under of the second crop of clover. l Waksman, S. A. 1922. :Microbiological Analysis. of Soil as an Index of Soil Fer· tility. III. Influence of Fertilization Upon the Numbers of Miroorganisms in the Soil. Soil Science 14: 321. 2 Waksman, S. A. 1923. Microbiological Anal)lsis of Soil as an Index of Soil Fertil-ity VI. Nitrification. Soil Science 16: 5 5. 3 Brown, P. E. 1911. Some Bacteriological Effects of Liming. Iowa Agr. Exp. Sta. Rsch. Bui. 2. 4 Brown, P. E. 1913. Bacteriolog-ical Studies on Field Soils. III. The Influence of Barnyard Manure. Iowa Agr. Exp. Sta. Rsch. Bui. 13. G Greaves, J. E. and Carter, E. G. 1916. Influence of Barnyard Manure and \Vater Upon the Bacterial Activities of the Soil. Jour. Agr. Rsch. 6: 889. 2Proceedings of the Iowa Academy of Science, Vol. 36 [1929], No. 1, Art. 11https://scholarworks.uni.edu/pias/vol36/iss1/11MICROORGANISMS I'.'J THE SOIL 81 Six samplings were made from these plots, four in the early fall of 1926 and two in the spring of 1927. The samples were secured by removing the top 2 inches of soil from an area about 6 inches square and the soil thoroughly mixed to a depth of about 7 inches. A sample was then drawn and mixed with 19 other similar samples taken elsewhere in the plot, to form a composite sample. The studies were all made on these composite samples from each plot. At each sampling the numbers of bacteria were determined, the nitrifying power of the soil was measured and the non-symbiotic nitrogen-fixing power of the soil was determined. The number of bacteria were determined by the usual dilution method, plating on Brown's albumen agar 6 and incubating 10 days at room temperature. The results shown in table I, indicate that the soil treatments Table I-Number of Bacter1:a Per Gram of Dry Soil DATE SAMPLED PLOTS OcT. 6 OcT. 12 Nov. 9 MAR. 19 APR. 2 AVERAGE 924 4,600,000 2,500,000 4,000,000 7,000,000 6,000,000 4,820,000 926 6,300,000 4,250,000 4,800,000 6,900,000 7,500,000 5,950,000 927 6,000,000 4,600,000 7,700,000 9,200,000 10,800,000 7,660,000 928 9,400,000 6,600,000 7,400,000 7,600,000 9,600,000 8,120,000 929 4,600,000 4,130,000 3,600,000 5,200,000 6,700,000 4,840;000 931 7,100,000 5,000,000 7,300,000 5,200,000 8,700,000 6,660,000 932 11,500,000 4,400,000 6,400,000 4,000,000 5,800,000 6~420,000 933 7,600,000 7,300,000 6,300,000 5,300,000 6,875,000 6,680,000 have a pronounced effect on the numbers of organisms present. Manure and lime increased the numbers and the rock phosphate and superphosphate gave further increases. The crop residues and lime had a large effect and the superphosphate with the residues and lime gave a further increase. The rock phosphate had little effect, on the average, but showed greater influence than the superphosphate at some samplings. There were some variations at the different elates of sampling but the effects of the treatments were ahvays shown, the variations occurring in the relative effects of the different treatments. The numbers of organisms present varied at the different samplings, the largest number being present in March .and April in the livestock or manure-treated series (plots 924-928) while in the grain· or crop residue series the grea.test numbers occurred at the early fall sampling. In general the treatments exerted large effects on these soils in 6 Brown, P. E. 1913. Methods for the Bacteriological Analysis of Soil. Iowa Agr. Exp. Station, Rsch. Bul. 11. 3Brown and Tomlin: The Effect of Various Treatments on Microorganisms in the Soil unPublished by UNI ScholarWorks, 192982 IOWA ACADEMY OF SCIENCE spite of some soil differences. The manure treated plots showed higher numbers on the average and greater effects from treatment although the soil is a Carrington or perhaps because it is a Car-rington, a soil less fertile than the Webster, which occurs on the grain system end of the series. Often, however, the Webster soils will respond to quite as large an extent as the Carrington to applications of a phosphate fertilizer. Rock phosphate usually does not give as large effects with residues as with manure and super-phosphate often brings about greater effects than rock phosphate when crop yields are measured. Apparently these bacteriological tests are quite in accord with general field observations on the effects of these soil treatments on crop growth. The nitrification tests were carried out by the method of W aks-man 7 using 100 gram quantities of soil in duplicate, without addi-tion, with 30 mgs. of ammonium sulfate added, and with 30 mgs. of ammonium sulfate and 210 mgs. of calcium carbonate supplied. The moisture content was brought up to the optimum and the cultures incubated for 4 weeks at room temperature, water being added every week to keep up the content. The nitrates present were determined by the phenoldisulfonic acid method. The results are given in table II. When no additions were made to the soil in the test, the differ-· Table II -Nitrification (Nitrates Present i·n· p.p.m.) PLOTS NITRIFICATION OF THE SOILS OWN NITROGEN 924 ---7 12 35 16 18 926 ---26 15 34 21 24 927 ---27 22 42 44 34 928 ---17 18 30 44 27 929 ---13 16 34 22 21 931 ---22 17 56 38 33 932 ---22 24 56 33 36 933 ---22 24 41 44 33 . N ITRIFICA1'ION' OF AMMONIUM S ULFA'l'E 924 55 42 74 15 83 53 926 80 118 144 26 178 109 927 106 212 236 21 239 163 928 155 184 176 147 263 185 929 100 98 84 17 I 131 106 931 154 167 163 103 156 149 932 651 355 325 1072 657 612 933 651 284 433 770 657 559 7 Waksman, S. A. 1923. Microbiological Analysis of Soil As an Index of Soil Fer-tility V. Methods for the Study of Nitrification. Soil Science 15: 241. 4Proceedings of the Iowa Academy of Science, Vol. 36 [1929], No. 1, Art. 11https://scholarworks.uni.edu/pias/vol36/iss1/11MICROORGANISMS IN THE SOIL NrTRIFICAT:rn~ OF AM:yroNIUM SuLFATE 1::1" THE PRESEKcE oF LIME 4 6 7 8 9 1 92 92 92 92 92 93 93 93 2 3 111 153 206" 413 230 400 425 391 74 153 275 275 131 237 284 317 --· 140 289 306 273 216 325 347 I 400 I 17 I 122 168 538 89 450 1072 898 2 63 57 OS 78 02 29 85 78 3 4 4 2 3 5 4 81 215 272 396 174 348 543 497 83 ences in nitrate content were too small to be significant. It does seem, however, that the treatments showed some effect. When am-monium sulfate was added in the test, the effects of the treat~ ments with manure, limestone, crop residues and the phosphates are very well shown, especially in the aver.age figures. There are some variations at the different samplings but in general the aver-ages reflect the differences shown at the various dates. With the addition of ammonium sulfate and calcium carbonate in the tests, the treatment effects are again quite evident. Manure and limestone evidently stimulate the nitrifying power of the soil to a considerable extent. This result is in accord with previous observations along this line. Rock phosphate and super-phosphate with the manure and lime have pronounced effects. The superphosphate seems to be greater in influence than the rock phosphate, in all the tests. Where crop residues and lime consti-tute? the basic treatment, however, the rock phosphate is about as effective as the superphosphate. This is the reverse of the results of the determinations of numbers. It may be noted that the soils in the crop residue plots are affected to a greater extent by the treatments, especially plots 932 and 933 which is undoubtedly due in part at least to the difference in soil types, these plots being on the Webster loam while the manure series plots are mainly on the Carrington loam. In general these results are in line with the numbers of organ-isms present in the soils, showing that the effects of the various treatments are very definite on the nitrifying power of the soils. The non-symbiotic nitrogen-fixation tests were carried out in Lipman's modified Azotobacter medium, using dextrose. One hundred cc. portions of the medium were sterilized in fl.asks, in-oculated with 5 gn1s. of soil and incubated for ten days at room temperature. The nitrogen fixed was determined by the regular Kjeldahl method, deducting the amount in the soil from the total content in the culture at the end of the incubation period. The results are given in table III. The results of these tests are not so definite as in the case of 5Brown and Tomlin: The Effect of Various Treatments on Microorganisms in the Soil unPublished by UNI ScholarWorks, 192984 IOWA ACADEMY OF SCIENCE Table I I I -- N on-Symbiotic N itragen Fi:rntion (Nitrogen fixed per gram of de.rtrose) DATE SAMPLED I PLOTS OcT. 6 OcT.12 OcT.26 Nov. 9 MAR. 19 APR.21 AVERAGE ----------------·--MGMS. MGMS. MGMS. MG:.VIS. MGMS. MGMS. 924 ---------1-.6-3A 3.0 2.50 2.1 1.9 2.9 926 3.8 2.5 1.6 2.6 4.1 3.4 3.00 927 4.6 3.7 5.1 3.2 3.8 2.8 3.90 928 4.6 4.6 3.6 4.7 3.8 2.5 4.00 929 3.5 2.5 1.3 2.9 3.7 4.0 3.00 931 2.1 4.2 4.4 4.3 2.7 3.0 3.50 932 3.7 5.4 3.6 4.2 3.9 3.5 4.05 933 4.3 2.7 3.6 3.8 4.2 5.6 4.05 the nitrification studies but the effects of the treatments of the soils are evidenced in the average figures. and in the data secured at each sampling. The .application of manure, limestone, rock phos-phate, superphosphate and crop residue evidently increases the fi:ication of nitrogen by the non-symbiotic organisms, stimulating their activities to an appreciable extent. With a more exact method of measuring the nitrogen-fixing power of soils, the results would undoubtedly be more definite. CONCLUSIONS These studies on a typical Wisconsin drift soil, under a five-year rotation system indicate very definitely that the .application of manure and limestone stimulates bacterial development to a very pronounced extent and increases in the nitrifying power and nitro-gen-fixing power of the soil are also noted. The addition of rock phosphate and superphosphate with the manure and limestone gives further increases in numbers of micro-organisms and in nitrification and nitrogen fixation. The super-phosphate generally seems tci have a greater stimulative effect than the rock phosphate which may be due to the solubility of the phos-phate or the presence of calcium sulfate in the superphosphate or to both. With the crop residues and limestone treatment increases were noted in numbers and in the nitrifying a:nd nitrogen-fixing activ-ities of microorganisms. The phosphate applied with the residues and limestone caused increases which in some cases were greater than with the manure and lime. However, the soil on the crop residue plots was a Webster loam to silty clay loam while that on the manured plots was a Carrington loam to fine sa11dy loam. The differences were probably clue to the variations in the soils on the two series of plots. In general the treatments affected the bacterial numbers, nitrification and nitrogen-fixation without regard to the variation in soil type. This is clue to the fact that the soils were very similar in the manure series of plots and in the crop residue series, and varied only between these series. 6Proceedings of the Iowa Academy of Science, Vol. 36 [1929], No. 1, Art. 11https://scholarworks.uni.edu/pias/vol36/iss1/11MICROORGANISMS IN THE SOIL 85 It seems evident from this work that such normal soil treat-ments as manuring, liming, the use of rock phosphate, superphos-phate and the addition of crop residues will stimulate bacterial development and such desirable activities as nitrification and non-symbiotic nitrogen-fixation. The beneficial effects of such treat-ments on crop yields, as so often and in fact, usually noted may be due, therefore, in part at least to effects on the soil microorgan-isms and their activities.' In some cases the most important effects of certain soil treatments are undoubtedly bacterial. IowA STATJ.t CoLLltGit, AME:s, IowA. 7Brown and Tomlin: The Effect of Various Treatments on Microorganisms in the Soil unPublished by UNI ScholarWorks, 1929

The Effect of Various Treatments on Microorganisms in the Soil under a Five-Year Rotation

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The Effect of Various Treatments on Microorganisms in the Soil under a Five-Year Rotation

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