212 SOIL CONDITIONS AND PLANT GROWTH 



Hart well and Pember, 1 and Tottingham and Hoffman, 2 failed 

 to find any increased solubility even when rock phosphate was 

 composted with stable manure. 3 



Decomposition of Organic Compounds. 



Many organic compounds surfer decomposition in the soil, 

 including some toxic to the higher forms of life and others 

 usually regarded as very stable. Among those readily de- 

 composed are phenol * potassium sulphocyanide, naphthalene, 

 pyridine and vanillin 5 : apparently the decomposition is 

 brought about in each case by micro-organisms. 



Some of these toxic substances may arise during the 

 ordinary decomposition processes in the soil, 6 and if so it is 

 obvious that the micro-organisms which further break them 

 down to innocuous compounds are playing an important part 

 in soil fertility. 



Swamp and Paddy Soils. 



In the East in India, Japan, etc. considerable quantities 

 of rice are grown on swamp soils, and the biochemical changes 

 differ considerably from those in normal soils. 



As already pointed out, nitrification does not go on but 

 the converse process, denitrification, occurs, so that if nitro- 

 genous artificial manures are to be used nitrates are out of 

 the question and organic manures and ammonium salts only 

 are possible (p. 210). 



1 Hartwell and Pember, Rhode Island Bull., 151, 1912. 



2 Tottingham and Hoffman, Wisconsin Research Bull., 29, 1913. 



3 For a summary of the recent work see Soil Sci., 1919, 7, 141. Solution 

 of the phosphate proceeded when sulphur was added (J. C. Lipman and McLean, 

 Soil Sci., 1918, 5, 243 and 533 ; also O. M. Shedd, Journ. Ag. Res., 1919, 18, 329). 



4 N. Sen Gupta, Journ. Ag. Science, 1921, II. For the organisms see 

 G. J. Fowler, Ardern, and Lockett, Proc. Roy. Soc., 1911, 83, 149-156, and 

 Wagner, Bied. Zentr. Agrik. Chem., 1915, 44, 212. 



6 W. J. Robbins and A. B. Massey, Soil Sci., 1920, 10, 237, also Ala. Expt. 

 St. Bui., 195, 1917, and 196, 1917 (M. J. Funchess). 



6 E.g. Liechti and Mooser (Land. Jahrb. Schweiz, 1906, i) estimate that 

 34-83 kilo of phenol per hectare (30-74 Ib. per acre) are formed during the de- 

 composition of an ordinary dressing of liquid manure. Of benzoic acid no less 

 than 400-500 kilos are supposed to be formed. 



