Although considerable work has been reported in the literature which shows some correlation between nitrification and the crop-producing power of soils, very little attention has been given to the significance of the soil reaction in nitrification studies. The object of this paper is to consider this problem and data are presented which show the relation of the reaction of the soil or its hydrogen-ion concentration to its nitrifying capacity

Erdman, Lewis W.

Humfeld, Harry

English

University of Northern Iowa

Proceedings of the Iowa Academy of ScienceVolume 34 | Annual Issue Article 81927The Significance of the Hydrogen-IonConcentration in Soil Nitrification StudiesHarry HumfeldIowa Agricultural Experiment StationLewis W. ErdmanIowa Agricultural Experiment StationCopyright © Copyright 1927 by the Iowa Academy of Science, Inc.Follow this and additional works at: https://scholarworks.uni.edu/piasThis 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 inProceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contactscholarworks@uni.edu.Recommended CitationHumfeld, Harry and Erdman, Lewis W. (1927) "The Significance of the Hydrogen-Ion Concentration in Soil Nitrification Studies,"Proceedings of the Iowa Academy of Science, 34(1), 63-66.Available at: https://scholarworks.uni.edu/pias/vol34/iss1/8THE SIGNIFICANCE OF THE HYDROGEN-ION CON-CENTRATION IN SOIL NITRIFICATION STUDIES HARRY HUMFELD AND LEWIS w. ERDMAN Although considerable work has been reported in the literature which shows some correlation between nitrification and the crop-producing power of soils, very little attention has been given to the significance of the soil reaction in nitrification studies. The object of this paper is to consider this problem and data are presented which show the relation of the reaction of the soil or its hydrogen-ion concentration to its nitrifying capacity. EXPERIMENTAL The soils used for this study were obtained from plots on the Agronomy Farm of the Iowa Agricultural Experiment Station. These plots have been under definite cropping systems and have received various fertilizer treatments regularly since 1914. All of the plots selected for this study were located on Carrington loam. The treatments of the plots and the rotations were as follows : PLOT NUMRER 817 818 820 822 823 824 826 828 905 906 907 908 1000 1001 1002 TREATMENT Check Manure and Lime Crop Residues and Lime Check Check Manure and Lime Crop Residues and Lime Check Check Manure Manure and Lime Lime Check Manure Manure and Lime 1005 Check 1012 Manure 1012 Manure and Lime 1016 Check 1018 Crop Residues and Lime 63 ROTATION Three year rotation Corn, Oats and Clover Three year rotation Corn, Oats and Clover Continuous Corn Five year rotation Wheat, Clover, Corn, Alfalfa and Oats 1Humfeld and Erdman: The Significance of the Hydrogen-Ion Concentration in Soil NitrifPublished by UNI ScholarWorks, 192764 IOWA ACADEMY OF SCIENCE Manure was applied at the rate of 10 tons per acre. Lime WiaS supplied in sufficient amounts to neutralize the acidity indicated by the Truog test, at the time the manure was applied. The continuous corn received this treatment once every four years; the three year rotation once during the rotation ahead of the corn; and the five year rotation was treated once during the rotation just before seeding of the alfalfa. On July 12, 1926, twenty samples were taken from each plot to the depth of 4-6 inches and thoroughly mixed in the field. A composite sample of the soil of each plot was then taken to the laboratory and moisture determinations made. The nitrification studies were carried out in the manner described by Waksman (2). Six samples of each soil equivalent to 100 grams of dry soil, were weighed into tumblers and brought up to the optimum moist-ure content, which was considered to be fifty percent of saturation. These samples were treated as follows : 1. Two samples were incubated to determine the nitrification of the soil's own nitrogen, that is, the samples were incubated at room temperature and at optimum moisture for thirty clays with-out any treatment. 2. Two samples were incubated to determine the nitrification of ammonium sulfate in the soil. To these samples 30 milligrams of nitrogen in the form of ammonium sulfate were added to each 100 grams of soil. All were incubated as in ( 1). 3. The two remaining samples were treated with ammonium sulfate as described above, and in addition 210 milligrams of cal-cium carbonate were added, in order to determine the power of the soil to nitrify ammonium sulfate in the presence of the theoretical amount of calcium carbonate needed to neutralize the acids formed by the complete oxidation of the ammonium sulfate. The amount of nitrates present before and after incubation was determined by the phenol-clisulfonic acid method, and they are reported as milligrams of nitrogen per 100 grams of dry soil. The initial and final reactions of the soils were determined by measuring the hydrogen-ion concentration by means of the quin-hyclrone electrode, as described by Biilman (l). RESULTS The results obtained in this study are presented in figure 1. The initial reaction of the soils was found to vary from as low a pH as 5.16 to as high a pH as 7.18. This is considerable variation for 2Proceedings of the Iowa Academy of Science, Vol. 34 [1927], No. 1, Art. 8https://scholarworks.uni.edu/pias/vol34/iss1/8SOIL NITRIFICATION STUDIES 65 soils of the same type and there is a good opportunity, therefore, to study the effect of the reaction of each sample on nitrification after incubation of the soils with the various treatments. It will be seen that in general, there is a fairly regular difference between the reaction of the soils before and after incubation. However, the difference tends to be greater when the initial acidity is compar-atively low, than if the soil is already r1uite acid. This in turn is reflected in the amount of nitrates formed. The indications are that nitrification goes on until a pH of 4.4 to 4.8 is reached while from then on it proceeds very slowly. \Vhen-ever the final pH is below 4.2 the amount of ammonium sulfate nitrifiecl is small. The data show that when calcium carbonate is added nitrification is increased considerably. This is clue, no doubt, to the more fav-orable reaction obtaining in the soil throughout the period of incu-bation. On the whole though, the final reaction of the soils is somewhat more acid than the initial reaction; which seems to indi-cate that a somewhat larger amount of calcium carbonate than the theoretical amount is necessary to completely neutralize the acidity produced. A few irregularities may be noted, which are probably due to differences in such factors, as previous cropping and treatment of the soil, the amount of organic matter and other buffer materials present, as well as differences in the available plant foocf content. There is also a very good correlation between treatments and nitrification. Manure plus lime gives the greatest increase in nitri-fication, closely followed by lime with crop residues and lime alone. Manure alone had no appreciable effect. The effect of rota-tion is also noticeable, nitrification in the soil on the plots under continuous corn is considerably less than where three and five year rotations are practiced. Also the correlation between soil acidity and nitrification is not nearly as good. On the whole, however, there is a close correlation between the soil reaction and the amount of ammonium sulfate nitrified. The results would seem to confirm \Vaksman's (2) statement, that, "when we compare the nitrifying capacity of two soils by the com-mon method of adding ammonium suHate to 100 grams of soil and determine the nitrates found after incubation, we actually measure not the nitrifying capacity of the two soils, but merely, in a roundabout way, the initial reaction. the buffer content, and the presence of neutralizing substances in the soil." 3Humfeld and Erdman: The Significance of the Hydrogen-Ion Concentration in Soil NitrifPublished by UNI ScholarWorks, 192766 IOWA ACADEMY OF SCIENCE LITERATURE CITED I. BrrLMAN, EINAR. 1924. On the measurement of hydrogen ion concen-tration in soil by means of the quinhydrone electrode. J our. of Agr. Sci. 14 :232-239. 2. WAKSMAN, SE:LMAN A. 1923. Microbiological analysis of soils as an index to soil fertility. V. Methods for the study of nitrification. Soil Sci. 15 :241-260. Iow A AGRICULTURAL ExPERIMENT STATION, AMES, IowA. 4Proceedings of the Iowa Academy of Science, Vol. 34 [1927], No. 1, Art. 8https://scholarworks.uni.edu/pias/vol34/iss1/8'f.O {,.o s.o +o \ \ . \ \ ·-'\ Bl/I .... 811 822 .SOii. nuJ' RNINIO/f/11/tf .St1J.T,,TC :\. \-·-... "\ ' \ \ \ \ \ .......... /NITl/11. p/I ., '·----. \ \ \ \ \ ... '·--· SOii. 'Pl..US HNIMONll/ht 8UJ.. FllTE Pl.US CllJ.CllJM CRlf.llON'llT/i:" 'f.O ~-0 s.o I I ' I I ~ ' II I ' ' I'--.. Tltrtt f1A4r ,,.tatiolf. 4';0 Clwf'• DllD 118 8111 811 SU. \ ,:\ ,, : I I I I ' I I I I • I \\ I • I I I I I I I I l'lirtt /e•r '!kth1iOll. C"'f• C,.r11 \ ,, ,' \ ~1 I• ! I» ..... 811 bJ '°' ,., '/Cl 'fOS ~I.OT NilM•CA #IT/IHT£ NITROHN FtNllL rH 'F°111fl ftlOr 1Pd&11011. c,..p-c-~ -1 \ \ \ .. I ' \ I I I \ i I I \ \._ \\ 30 ' 10 IOIJ lt>IB /mt. /QI/, \ ~. I I I I I I I ' I I I I ' ' ' I I I TliY }"etlr .... /IJ 71»1>""". I c~,-w~ 10/3 10/IJ /Oil;,~,. Figure 1. Showing correlation between nitrification and the reaction of the soils before and after incubation. 5Humfeld and Erdman: The Significance of the Hydrogen-Ion Concentration in Soil NitrifPublished by UNI ScholarWorks, 1927

The Significance of the Hydrogen-Ion Concentration in Soil Nitrification Studies

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The Significance of the Hydrogen-Ion Concentration in Soil Nitrification Studies

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