122 EXPERIMENT STATION KECOED. 



Applications of manure up to 16 tons per acre increased the number of organ- 

 isms in, and also tbe ammonifying and nitrifying powers of the soil. The greatest 

 increases occurred between the untreated soil and that receiving 8 tons per acre, 

 and between the latter and that to which 12 tons per acre were applied. " In 

 most cases only a very slight increase occurred in the soil on which 16 tons 

 were used over that where 12 tons were added. Twenty tons of manure per 

 acre caused a depression in numbers of bacteria, in ammonifying power, and in 

 nitrifying power, . . . the results being lower than those secured when 12 

 tons per acre were added." There was a close relationship between the ammo- 

 nifying power of the soils and the number of organisms present. 



Albumin agar permitted of the development of larger numbers of soil organ- 

 isms, and also a greater differentiation between the soils of the various plats, 

 than the modified synthetic agar. " The casein fresh soil method of testing the 

 ammonifying power of the soil was the simplest, permitted of the greatest dif- 

 ferentiation between different soils, and in general was the most satisfactory. 

 The ammonium sulphate fresh soil method for testing the nitrifying power of 

 the soil showed the greatest differences between the various soils and is recom- 

 mended as the more rational method. 



" The nitrifying power and the ammonifying power of the soil . . . proceeded 

 in the same direction. 



"Applications of manure up to 16 tons per acre increased the yield of corn 

 from the i)lats in this series, the greatest increases occurring between the 

 [untreated] plat and that receiving 8 tons per acre, and between the latter 

 and the plat to which 12 tons per acre were added. A very slight further 

 increase occurred when 16 tons per acre were applied. Twenty tons of manure 

 per acre depressed the crop yield below that obtained when 12 tons per acre 

 were added. 



" The results of the bacteriological tests and the crop yields coincided almost 

 exactly, [indicating] . . . that there is a close relationship between bacterial 

 activities and the fertility or crop-producing power of soils. The depression in 

 crop yields and bncterial activities caused by 20 tons of manure per acre can 

 not be attributed to denitrilication, as tests by the Giltay solution method and 

 the soil method give no evidence of losses of nitrogen. The depression must 

 therefore be due to physiological or other causes." 



Farm manures, P. Et Brown (loica Sta. Circ. 9 (1913), pp. 3-16, figs. 2).— 

 This is a popular presentation of the character, value, and importance and 

 methods of using manure of farm animals. 



Green manuring' and soil fertility, P. E. Brown (Iowo Sta. Circ. 10 (1913), 

 pp. 3-15. flfjs. 6). — The value and importance of green manuring, especially for 

 Iowa soils, are popularly presented. 



[Cave deposits, manures, limes, and limestones], H. J. Vipond (Union So. 

 Africa Dept. Agr. Rpt. 1912-13, pp. 304, 305). — ^Analyses of these materials for 

 fertilizing constituents are reported. 



Report of the superintendent of the guano islands, W. R. Zeederberg 

 (Union So. Africa Dept. Agr. Rpt. 1912-13, pp. 351-355). — The guano islands, 

 lying mainly along the west and southwest coasts of South Africa, yielded 

 during 1912 6,372J tons of guano having the following average composition: 

 Niti-ogen 11.51 per cent, potash 2.20. phosphoric acid soluble in water 3.04, 

 phosphoric acid soluble in citrate solution 9.25, total phosphoric acid 9.62, and 

 lime 9.G6 per cent. The supply was much less than the demand for home 

 consumption. 



Peat, C. A. Davis (U. S. Oeol. Survey, Mineral Resources of the United 

 States, 1912, pt. 2, pp. 497-501). — This article deals briefly with the production 



