INFLUENCE OF ENVIRONMENTAL CONDITIONS 



783 



has been demonstrated. 52 At the lower limits of moisture, less water 

 is required to start nitrification in sand than in claj'' soils; at the higher 

 limits of moisture, less water is required to stop nitrification in sand 

 than in clay. The optimum for the two soils varies; a rise above the 

 optimum is more injurious than an equal fall below the optimum. 

 Table 89 gives the results obtained 53 on the influence of moisture upon 

 the decomposition of organic matter in the soil as measured by 

 CO2 production. 



The nature of the soil is also found to be an important factor in 

 modifying the influence of moisture upon microbiological activities 

 in the soil, as shown in table 89 and in the following summary: 54 



Tenacious clay soil 



Diluvial loam 



Alluvial soil 



CARBON 



CONTENT OF 



SOIL 



per cent 



1.68 

 2.12 

 1.73 



CO: PRODUCED 

 IN 24 HOURS, 

 BY 1 KGM. OF 

 FRESH SOIL 



mgm. 



8.2 

 14.6 

 36.6 



CO2 PRODUCED 

 IN 24 HOURS 

 BY 1 KGM. OF 

 SOIL, STERI- 

 LIZED AND 

 INOCULATED 



mgm. 



14.0 



27.8 

 59.8 



Winogradsky 55 found that, in the case of a soil with a moisture holding 

 capacity of 48 per cent, 15 per cent moisture favored the development of 

 aerobic bacteria to a depth of 23 cm.; 19 per cent moisture to 18 cm.; 

 21 per cent moisture caused the anaerobic bacteria to develop a few 

 centimeters below the surface, while 24 per cent moisture and above 

 made the soil decidedly favorable for anaerobic bacteria. Nitrogen 

 fixation was found 56 to be at a maximum near the point of saturation; 

 even higher nitrogen fixation was recorded under anaerobic than under 

 aerobic conditions. 57 In some cases two maxima were recorded 58 - 59 for 



62 Patterson, J. W., and Scott, P. R. The influence of soil moisture upon 

 nitrification. Jour. Dept. Agr. Victoria, 10: 275-282. 1912. 



63 Konig, J., and Hasenbaumer, J. Die Bedeutung neuer Bodenforschungen 

 fur die Landwirtschaft. Landw. Jahrb., 55: 185-252. 1920. 



54 Stoklasa, 1926 (p. XIII). 



63 Winogradsky, 1924 (p. 542). 



66 Traaen, A. E. tlber den Einflusz der Feuchtigkeit auf die Stickstoffum- 

 setzungen im Erdboden. Centrbl. Bakt. II, 45: 119-135. 1916. 



17 Panganiban, 1925 (p. 777). 



"Greaves and Carter, 1917 (p. 774). 



69 Lipman, C. B., and Sharp, L. T. Effect of moisture content of a sandy 

 soil on its nitrogen fixing power. Bot. Gaz., 59: 402-406. 1915. 



