898 Journal of Agricultural Research vol. vi.no. 23 



Both the water and the manure applied make a marked difference in 

 the ammonifying powers of the soil. It is lowest in those pots which 

 received no manure and gradually increases when 5, 10, 15, 20, and 25 

 tons of manure are applied. The water likewise has a noticeable effect 

 on the ammonifying powers of the soil. In the unmanured soil it in- 

 creases until 20 per cent of water is applied, at which point it reaches 

 its maximum. When more than this quantity of water is applied, the 

 ammonification is retarded. It is not as great when 22.5 per cent of 

 water is applied as in the presence of only 12.5 per cent. Similar results 

 are obtained when various quantities of water are applied in the presence 

 of 5 tons of manure per acre. Here the influence of the water is much 

 more pronounced than it is in the absence of manure. It reaches its 

 maximum effect when 20 per cent of water is applied. In the presence 

 of 10 tons per acre of manure the higher percentages of water have much 

 greater influence on the ammonifying powers of the soil than do the lower 

 percentages of water. In the presence of 20 tons of manure the water 

 also exerts a great influence, but here the higher percentages produce a 

 depressing effect, which becomes very perceptible in the pots which have 

 received 25 tons of manure to the acre. It is interesting to note that 

 with 25 tons of manure 15 per cent of water gave better results than 

 either higher or lower percentages of water. It is quite possible that the 

 higher water content in the presence of large quantities of organic matter 

 produce anerobic conditions which are not fully compatible with the 

 best bacterial activities. The results are brought out more fully in 

 figure 1 , on the horizontal line of which is given the percentage of water 

 applied to the soil, while on the perpendicular line is given the milligrams 

 of ammonia produced in 100 gm. of soil. 



If we consider the average quantity of ammonia produced in the 

 unmanured pots as 100 per cent, that produced on the various manured 

 pots becomes, with 5 tons of manure, 122 per cent; with 10 tons of manure, 

 140 per cent; with 15 tons, 152 per cent; with 20 tons, 160 per cent; and 

 with 25 tons, 181 per cent. The average increase per ton of manure 

 applied is greatest when 5 tons to the acre are applied and becomes 

 gradually less as the quantity of manure applied becomes greater. If 

 we consider the average percentage of ammonia produced in the soils 

 receiving 12.5 per cent of water as 100, then the soil receiving 15 per cent 

 of water produced no per cent; the soils with 17.5 per cent of water 

 produced in per cent; the soils with 20 per cent of water, 123 per cent; 

 and those receiving 22.5 per cent of water produced 119 per cent of 

 ammonia — a gradual increase in the ammonia produced until the quantity 

 of water applied exceeded 20 per cent. 



The application of manure to a soil produces a very great increase in 

 the nitrifying powers of the soil. The quantity of nitrates produced 

 is very low in the soil receiving no manure but is greatly increased with 

 the application of manure, even with so large a quantity as 25 tons per 



