lo May. 1 912.] /n-fliHin-c of Soil Moisture ufon Nitrification. j8r 



Df the laboratory, it held 2.35 per cent, of moisture. As seen from the 

 top line in both tables, neither of these amounts is sufficient to maintain 

 nitrification. In the 90 per cent, of saturation introduced in the second 

 experiments, the result was poor owing probably to the water excluding air 

 from the pores of the soil. If, as would appear, the best degree of 

 saturation for this soil runs from 40 to 70 per cent., the figures indicate that, 

 beyond those limits, increasing wetness acts more sharply than increasing 

 dryness. 



Table VI. gives the results on the clay soil. 



Table VI. 



Referring to their mechanical analyses, and the water content of the 

 two varieties of soil, it was apparent that clay holds its water more firmly 

 than the sand. The effect of this is now seen upon the nitrifying action, 

 because while with sand it was the driest series only which remained 

 stationary, with clay the second driest also failed to act. With sand, 5.35 

 per cent, of water induced nitrification although slowly, with clay it had no 

 effect. With sufficient moisture, nitrification proceeded rapidly in the clay, 

 and the water optimum is apparently higher with clay than sand. This is 

 no doubt owing to its greater absorptive power, and in connexion with this 

 it is further noticeable that the largest supply of water (24.08 per cent.) 

 which ga\e a very poor result with sand gave a high return with the clay 

 soil. 



On comparing the last columns of tables V and VI. it will be ob- 

 served that nitrification was altogether more active in the clay than the 

 sand. In the best case of the former just over 90 per cent, of the total 

 nitrogen was nitrified. This result closely agrees with Professor Wagner's* 

 investigations into the comparative effects of nitrate of soda and sulphate 

 of ammonia, when applied as manures. Referring to the chemical analyses 

 above, it was noticed that the clay soil probably contained sufficient avail- 

 able base, while the sand was deficient in lime — as are a large number of 

 Victorian soils. It is not clear that this deficiency has affected in kind the 

 action of soil moisture in promoting nitrification, although in the sandv soil 

 it has probably affected it in degree. Lime, however, lies outside the scope 

 of the present experiments — their object was rather to obtain experimental 

 data on the relation of moisture to nitrification in two types of Victorian 

 .soils as they came to hand. 



The effect upon nitrification of lime and other substances added to the 

 soil will be investigated in a future set of experiments. 



* Die Stickstoflfdiinguug der landw. ICultiirpflanzen, by Prof. Dr. Paul Wagner. Berlin, Pru' Parey. 



