420 EXPERIMENT STATION RECORD. 



variations in soil temperature at depths of 1, 6, 12, and 24 in. from the surface 

 are graphically reported. 



These results show that at the 1-in. depth the soil is exposed to wide ranges 

 of temperature and that as the depth increases the temperature variations 

 decrease in amplitude. At the 24-in, depth the daily variations are practically 

 negligible. " Each curve cuts each other curve at least twice during the year. 

 For a certain period the upper layer of soil is giving and for the remainder of 

 the year is receiving heat from the layer above or below. In the warm months 

 of the year the 1-in. curve occupies a position above the other curves, but 

 during the cold period the positions are entirely reversed. . . . The increase 

 of temperature from spring to summer is more rapid than the decrease from 

 autumn to winter." 



From observations on transpiration and evaporation by wheat, oats, barley, 

 and alfalfa grown under soil temperature conditions comparatively identical 

 with those of the above experiments, it is inferred that " vegetative growth as 

 far as the Werribee soil was concerned was never at a standstill at any period 

 of the year." 



Influence of growth of cowpeas upon some physical, chemical, and biologi- 

 cal properties of soil, C. A. LeClaik {U. S. Dcpt. Apr., Jour. Agr. Research, 5 

 (1915), No. 10, pp. Jf39-Jf48, pi. 1, flga. 2). — A historical summary of work bear- 

 ing on the subject is given and experiments conducted at the ^lissouri Experi- 

 ment Station with a silt loam soil are reported, the main purpose of which was 

 to study the influence of the growth of co\^'peas on the soil compactness and its 

 nitrate content. 



"The data given show conclusively that cowpeas tend to maintain the fria- 

 bility of loose and compact seed beds. . . . AVhile cowpeas take more water 

 from the soil than evaporates from uncultivated adjacent lands, the removal 

 of water is from below the second foot of soil. Land that was plowed and left 

 uncultivated or plowed and seeded to cowpeas contained a greater quantity of 

 nitrates in the soil at the end of the season than unplowed land similarly 

 treated. Tlie bacterial activities of the soil upon which co\\T)eas were grown 

 tended to show tliat the soil organisms are probably a factor in preventing the 

 packing of soil as also is the mechanical shade effect of the crop grown upon 

 the land." 



Oxidation of organic matter in the soil, G. S. Fraps (Texas Sta. Bui. 181 

 (1915), pp. 5-27). — Laboratory experiments with 25 soils, varying in texture 

 from fine sand through sand, fine sandy loam, and clay loam to clay, are re- 

 ported, the purpose of which was to study the oxidation of natural organic 

 matter in soil and of different kinds of added organic matter in soil by moans 

 of the loss on ignition and of the carbon dioxid produced ; and the influence of 

 the quantity of water in the soil, the method of adding it and of calcium car- 

 bonate on carbon dioxid production. 



It was found that the oxidation of organic matter as measured by the loss 

 on ignition of the soil was rapid during the first three weeks, after which the 

 loss on ignition was irregular. " Corn chop, rice hulls, wheat shorts, and wheat 

 bran were oxidized 72 to 81 per cent in 81 weeks, as measured by loss on 

 ignition. Meat tankage and blood were oxidized 47 to 68 per cent. Excrement 

 and bat guano were oxidized 15 to 22 per cent." 



On the basis of carbon dioxid production "cotton-seed meal was rapidly oxi- 

 dized, about 10 per cent in one day, and nearly 30 per cent in four days. In 

 another experiment, 38.8 per cent of the carbon of cotton-seed meal, 10.1 per 

 cent of the manure, and 8.8 per cent of the corncobs were oxidized in the first 

 week. Oxidation decreased rapidly after the first week. With cotton-seed meal, 

 the oxidation of each succeeding week was about one-half of the preceding 



