906 



Journal of Agricultural Research 



Vol. VI, No. 23 



duced by the unmanured, and the addition of water up to 10 inches pro- 

 duces a beneficial effect. The great effect, however, is noted on those 

 soils which receive 15 tons of manure per acre. Here, also, the ammoni- 

 fying powers are accelerated by the application of irrigation water up to 

 10 inches. Above this there is a depressing effect just as was noted in the 

 pot experiments and can very likely be accounted for on the same 

 grounds. In midsummer the influence of manure is just as perceptible 

 as it is in the spring, and the influence of the water becomes much more 

 regular, but still follows the same general trend that it did in the spring. 

 In the fall the manure is found to exert almost quantitatively the same 

 effect as it does in spring and midsummer. The depressing effect of the 

 larger quantities of water during this season of the year is not as great 

 as it is earlier in the year. But even here the higher applications (20 to 

 40 inches) cause a great falling off in the ammonifying powers of both 

 the manured and unmanured soils. These results are brought out graphi- 

 cally in figure 4. 



Table V. — Quantity of ammonia (in milligrams) produced in four days in 100 gm. of soil 

 containing 2 gm. of dried blood — fallow plots 



