720 EXPERIMENT STATION RECORD. [Vol.41 



Chemical reactions of the soil, Martin and Wirbel {Ann. Chim. Analyt., 2. 

 ser., 1 (1919), No. 8, pp. 246-252). — This is a brief review of studies on the 

 chemical reactions in soil between acid and silkaline soil solutions and the 

 effect thereon of soil colloids. 



It is concluded that clay, silica, and humus should be considered not 

 especially as colloids possessing the power of absorbing the bases of soluble 

 fertilizers, but more particularly as catalyzers permitting a speed of reaction 

 between salts in accordance with the more or less rapid transformation of 

 the character of the soil. It is thought that precipitated phosphate should 

 give as good results as superphosphate in soils, on the grounds that under 

 the influence of soil colloids and calcium carbonate in the presence of alkaline 

 salts a gradual dissolution of the phosphate takes place. The improvement 

 of tough soils by the incoiijoration of organic matter is explained on the 

 basis that the presence of so-called humic acid prevents the dissolution of 

 silica to a large extent. It is further pointed out that the manner of fixation 

 and dissolution of phosphoric acid in soil is the same as that of potash or 

 ammonia. 



Soils and soil conditions, W. H. Harrison (Sci. Rpts. Agr. Research Inst. 

 Pusa, 1917-18, pp. 27-30). — Studies of the relationship of the gaseous products 

 of decomposition to paddy soils have shown that carbon diosid when present 

 alone can persist as such, but that in admixture with hydrogen and under 

 biological influences a recombination occurs of such intensity that the absence 

 of any large quantity of these gases from the atmosphere in paddy soils is 

 accounted for. Incidentally, distinct evidence has been obtained to show that 

 marsh gas can be produced by a combination of these two gases under biological 

 influences. The important fact has also been obtained that this reaction be- 

 tween carbon dioxid and hydrogen is not peculiar to paddy soils, but that it 

 can be induced in dry soils with the utmost ease when the conditions are 

 approximately anaerobic in character. 



Pot experiments with sterile so-called " bara " soils after the salts present 

 had been washed out with ordinary water resulted in the almost entire inhibi- 

 tion of germination. An examination of the soil showed that the bicarbonate 

 of lime in the water had brought about a reaction leading to the production 

 of alkaline carbonate in the soil. The soil experimented with originally con- 

 tained a comparatively small amount of alkaline carbonate and a considerable 

 proportion of sulphates and chlorids, whereas after the washing process the 

 sulphates and chlorids were reduced in amount, but the carbonate content had 

 considerably increased, so that the effect had been to change the original 

 condition of white alkali into one of black alkali. 



Preliminary experiments in relation to the reactions occurring between cal- 

 cium phosphates and calcium carbonate under varying conditions showed that 

 " supeiphosphate reacts very rapidly at oi-dinary temperature with calcium 

 carbonate, the product of the reaction being the comparatively insoluble dical- 

 cic phosphate, and that the latter in turn slowly reacts with more CaCOa 

 forming tricalcic phosphate. At higher temperatures the intermediate stage 

 practically disappears and tricalcic phosphate is formed with gi-eat rapidity.'' 



Soil biolog'y, J. Mackenna {Rpt. Prog. Agr. India, 1917-18, pp. 101-103). — 

 Field studies on the seasonal variation and effect of cropping and of fallow 

 on .soil nitrification showed that the presence of a crop, while diminishing the 

 apparent amount of nitrification as measured by the nitrate found in the soil, 

 actually increased the amount if it is assumed that the crop takes its nitrogen 

 entirely as nitrate. Experiments on the specific nature of various strains of 

 Baoilltus radicicola and upon apparent symbiotic fixation of nitrogen without 



