1918] SOILS FEETIOZEES. 117 



These soils wei'e also generally deficient in calcium carbonate, and contained 

 relatively large amounts of organic matter and potash. The phosphoric-acid 

 content was relatively high in the silt loams and low in the sands. 



The influence of soil conditions on the decomposition of org'anic matter in 

 the soil, E. J. Russell and A. Applet ard (Jour. Agr. Sci. [England], 8 {1917), 

 No. S, pp. 385-417, figs. 9). — Studies conducted at the Rothamsted Experiment 

 Station on the changes in bacterial numbers, nitrate content of the soil, and 

 carbon dioxid content of the soil air are reported, these having been determined 

 at frequent and regular intervals during several seasons on five different plats 

 of land. The results are graphically presented. 



" There is sufficient resemblance between the curves for bacterial numbers, 

 carbon dioxid (except for a period on cropped land), and nitrate to justify the 

 conclusion that they are all related. The curve for nitrate, however, is always 

 behind that for bacterial numbers, the lag amounting to two or three weeks. 

 Assuming . . . that the curves are connected, this would indicate two stages 

 in nitrate production, one related to the bacterial numbers, the other not. . . . 



" The biochemical decompositions in the soil are determined in the first in- 

 stance by the temperature and do not proceed to any notable extent below 5° C. 

 As soon as the temperature rises action begins rapidly ; but it soon slows down 

 and other factors begin to operate. Moisture is one of these. Action came to a 

 minimum in June, when the moisture fell to 10 per cent by weight of the un- 

 manured soil and 15 per cent by weight of the dunged soil, or 16 and 22 parts, 

 respectively, by volume, assuming there was no contraction. Rainfall is an even 

 more important factor, a shower of rain having a notable effect in starting the 

 decompositions. It seems probable that the dissolved oxygen is an important 

 factor here. The growing crop exerts a depressing effect, though whether by 

 taking up the dissolved oxygen, by giving out carbon dioxid, or by some other 

 action, is not clear. The fluctuations in bacterial numbers are not wholly 

 explicable as functions of the temperature and moisture content." 



Changes in the physical composition caused by the conversion of dry soil 

 into paddy soil, W. H. Harrison {Madras Agr. Dept. Year-hook, 1917, pp. 73- 

 76). — Experiments are reported and the conclusions drawn that "wet methods 

 of cultivation when first applied to dry soils tend, in the first instance, to bring 

 about a redistribution of the soil particles between the soil and subsoil. The 

 tendency is for the coarse particles to accumulate in the subsoil and the finer 

 particles in the soil. Afterwards the main tendency is to cause a rapid break- 

 ing down or weathering of the particles both In the soil and subsoil, thus caus- 

 ing the soils to become heavier in character." 



Forms of occurrence of phosphoric acid in soil, M. A. Jeqoeov {fuzh. Russ. 

 SelsJc. Ehoz. Qaz., 1916, Nos. 13-14, PP- 4, 5; 15, pp. 4< 5; abs. in Internat. Inst. 

 Agr. [Rome], Internat. Rev. Sci. and Pract. Agr., 7 {1916), No. 9, pp. 1248, 1249; 

 Jour. Soc. Chem. Indus., 36 {1917), No. 5, p. 298).— Experiments with podzol 

 soil containing 0.0532 per cent phosphoric acid and two chernozem soils con- 

 taining 0.145 and 0.11 per cent phosphoric acid are reported, in which the 

 organically combined phosphorus was separated and estimated by washing the 

 soil with 3 per cent hydrochloric acid and treating with 3 per cent ammonia 

 solution, the resulting solution being then filtered and precipitated with lead 

 acetate. 



" The washed precipitate, freed from lead with hydrogen sulphid, was re- 

 dissolved in dilute ammonia, the liquid filtered, concentrated, and finally ex- 

 tracted with ether, the organic phosphorus going into solution. ... Of the 

 total phosphoric acid In these soils, the ammonia solution removed about one- 

 half in the first and third, and one-third In the second. The organic phosphoric 

 acid extracted varied from 10 to 17.67 per cent of the total phosphoric acid. 



