SOILS FERTILIZERS. 721 



The effect of green manuring on soil nitrates under greenhouse condi- 

 tions, H. H. Hill et al. (Virginia Sta. Tech. Bui. 6 (1915), pp. 121-153; Rpts. 

 1913-14, pp. 121-153). — Pot and laboratory experiments to determine the effect 

 of green manures on nitrate accumulation and plant growth in 5 types of Vir- 

 ginia soils are reported. 



Preliminary experiments on the effect of vegetable matter on nitrate formation 

 in partially sterilized and unsterilized silt loam showed that organic matter such 

 as blue grass, clover, and alfalfa when turned under in the soil appeared to pass 

 over into nitrates, more especially in sterilized soil. 



In further experiments with soils ranging in texture from sandy loams to heavy 

 clays to which green manures and organic matter were added in the following 

 proportions : 0.3 per cent Swedish filter paper, 0.6 per cent straw, 0.44 per cent 

 clover, 0.44 per cent soy beans, and 0.22 per cent blue grass, it was found that 

 the total number of bacteria in soils treated with green manures was much 

 greater than in soils receiving no green-manure treatment. Legumes gave in 

 most cases the highest bacterial count. The rate of nitrate formation and 

 plant growth in every case was greatly improved by the addition of green 

 manures. There was a smaller amount of nitrogen in plants grown in pots 

 treated with paper than with those grown on untreated soil. Paper in each 

 soil type caused a depression in the number of bacteria, nitrate formation, and 

 in plant growth, and produced a yellow appearance in the plants. 



" Soils vary in their power to accumulate nitrogen. Soils, from the same field, 

 when taken at different times, show a variation in nitrogen-accumulating 

 power." " It is believed from the results of this paper that the open soils have 

 a natural tendency toward nitrate accumulation and that this may be stimu- 

 lated by applications of green materials." 



A bibliography is appended. 



Some common misconceptions with respect to soils and soil fertility, O. B. 

 LiPMAN {Mo. Bui. Com. Hort. Cal., 4 (1915), No. 5-6, pp. 23i-239).— In an 

 attempt to correct certain of what are considered to be misconceptions with 

 reference to soils and soil fertility, it is pointed out that in the light of present 

 knowledge overirrigation is injurious to crop growth, that analysis of soils is 

 not a criterion for their adaptability to crops or fertilizer needs, and that plant- 

 food elements in fertilizers do not have many of the specific effects on plant 

 growth commonly attributed to them. 



The teachings of the Kentucky Agricultural Experiment Station relative 

 to soil fertility, G. Robekts (Kentucky Sta. Bui. 191 (1915), pp. 31-66).— This 

 bulletin, with an introduction by J. H. Kastle, is a general statement of the 

 principles of soil fex'tility as taught by the station. These are based in part 

 on a previous bulletin (E. S. R., 21, p. 316) and in part on the general results 

 of two, four, and six year series of plat and field experiments in different parts 

 of the State with various field crops to determine the fertility requirements of 

 representative soil types, with particular reference to phosphorus, nitrogen, 

 and potash, and the most effective and economical methods of supplying these 

 when needed. The detailed results of these experiments are to be published 

 in a later publication. 



It is the belief that practically all the soils of Kentucky contain inexhaustible 

 supplies of potash, which can be made available with sufficient rapidity through 

 maintenance of the humus content. With the exception of the soils of the blue- 

 grass regions, the soils of the State are considered to be deficient in phosphorus, 

 which usually can be most advantageously supplied as acid phosphate until 

 organic matter is restored to the soil, after which rock phosphate may be used. 

 The purchase of nitrogenous fertilizers is considered uneconomical, nitrogen 



