1«16] SOILS — FERTILIZERS. 815 



" The maximum number of bacteria were obtained from the soil receiving 15 

 tons of manure. The application of irrigation water up to 20 in. increased the 

 bacterial count, being most noticeable in the soil receiving the greatest quantity 

 of manure. If the ammonifying powers of the unmanured soils are considered 

 as 100 per cent and the unirrigated as 100 per cent, the manured and irrigated 

 soils then become with 5 tons of manure, 147 per cent ; with 15 tons of manure, 

 188 per cent ; 5 in. of water, 106 per cent ; 10 in. of water, 117 per cent ; 20 in. 

 of water, 108 per cent ; 30 in. of water, 106 per cent ; and 40 in. of water, lOS per 

 cent. Large quantities of irrigation water produced the greatest depressing 

 effect in the presence of 15 tons of manure per acre. The application of ma- 

 nure to a soil increases its nitrifying powers. The application of irrigation 

 water to a fallow soil apparently depresses its nitrifying powers. Fewer organ- 

 isms develop on synthetic agar from a cropped than from a fallow soil. The 

 application of manure to a cropped soil increases the bacterial count of the soil. 

 The greatest number of organisms developed from the soil receiving 10 in. of 

 irrigation water. 



" The ammonifying powers of the cropped soils were slightly lower than 

 similarly treated fallow soils. The application of 5 and 15 tons of manure per 

 acre to a soil increases the ammonifying powers of the soil. The application of 

 irrigation water up to 30 in. increases the ammonifying powers of the soil. 

 The greatest increase resulted in those soils receiving 15 tons per acre of 

 manure. The application of 40 in. of irrigation water to corn land, especially 

 to that receiving 15 tons of manure per acre, depresses the ammonifying powers 

 of the soil. 



" The nitrifying powers of fallow soil were higher than similarly treated 

 cropped soils. The application of manure to a cropped soil greatly increases 

 its nitrifying power. The application of irrigation water up to 30 in., especially 

 to a soil receiving 15 tons of manure per acre, greatly increases its nitrifying 

 powers. 



" There was found to be a direct relationship between the bacterial count, the 

 ammonifying powers, the nitrifying powers, and the crop produced on a soil 

 receiving no manure, 5 tons, and 15 tons of manure per acre. A close correla- 

 tion was also found to exist between the bacterial activities of soil receiving 

 varying amounts of water and the crop produced upon the soil." 



A list of 52 references to literature bearing on the subject is appended. 



The value of manxire as compared with chemical fertilizers, C. E. Thobne 

 {Mo. Bui. Ohio Sta., 1 {1916), No. 8, pp. 253, 254).— A review of experimental 

 work at the staton shows that " open-yard manure of good quality should not 

 cost more than about $2 a ton and manure fresh from the stable not more 

 than $2..50 a ton, spread on the field, as compared with nitrate of soda at $60 

 a ton, 16 per cent acid phosphate at $18, and muriate of potash at $50 properly 

 compounded and spread on the field." On the other hand it is pointed out that 

 100 tons of manure produced annually from well-fed animals and used in a 

 systematic rotation of crops and supplemented with acid phosphate, bone meal, 

 or raw rock phosphate may be expected to produce as large an increase in 

 crops as an annual expenditure of $200 to .$250 in chemical fertilizers. 



The decomposition of the organic matter of kelp in the soil, A. W. Christie 

 {Jour. Indus, and Engin. Chem., 8 {1918), No. 5, pp. Jf2o-'.'t21 ; abs. in CJiem. Abs., 

 10 {1916), No. 11, p. 1571). — Experiments conducted :jt the California Experiment 

 Station on the extent and rate of decomposition of kelp in fine sandy loam soil 

 as compared with manure, straw, and alfalfa are reported. The two samples 

 of kelp used were Macrocystis pyrifera and Nereocystis leutkeana. It was 

 found that " dried and ground kelp decomposes in the soil under laboratory 



