1919] SOILS FERTILIZERS. 813 



" By extrapolating the curve thus obtiiined, an approximation for the limiting 

 value of the shrinkage in the case of pure colloidal clay is arrived at amounting 

 to approximately 23 per cent. On this assumption it becomes possible to calcu- 

 late the approximate content of colloidal material in any soil from a knowledge 

 of the linear shrinkage. Results are adduced showing the values obtained for 

 the shrinkage in the case of separated line silt and clay fractions in the case 

 of two soils of known shrinkage and physical composition, and compared with 

 the values calculated from previous assumptions." 



The influence of stones in soil on the growth of plants, T. PFErFFEE, W. 

 SiMMEKMACHEK, and 11. Fkiske {Landw. Vers. Sta., 93 (1919), No. 1-2, pp. 49- 

 6S, fig. 1). — Pot culture experiments with oats on a productive loam soil mixed 

 with stones so that the pots contained 25, 50, 75, and 100 per cent of loam are 

 leported. 



It is concluded that a very high stone content in soil does not cause any 

 considerable loss of energj.- through the root development of oats and similar 

 crops. It was found that there was practically no difference in the available 

 water and plant nutrients in the different soils, and the yield of dry matter 

 varied only within the limits of error. It is further concluded that soil volume 

 as such has no direct influence on plant growth. 



Soils and manures (Bd. Agr. and Fisheries [London], Guides Small Hold., 

 No. 6 {1919), pp. 30). — This pamphlet gives brief popular information on the 

 subject for the benefit of service men intending to settle on the land. 



Some experiments on sand hill land: Tillage, fertilizer, and crop adapta- 

 tion, A. G. Smith and O. O. Camp (<S'. G. Dcpt. Agr., Gom. and Indus., Bui. 63 

 U918), pp. 20, fig. 1). — General soil development experiments are reported, the 

 purpose of which was to determine the proper treatment and crops for coarse 

 sandy soil, usually with yellow sandy subsoil. 



It was found that deep breaking of sandy lands was generally more profitable 

 than shallow breaking, although in some years shallow breaking gave the better 

 results. Barnyard manure was more profitable when applied to cotton than to 

 other crops. Manure drilled gave higher yields of cotton than manure broad- 

 casted. In a comparison of acid phosphate, basic slag, and rock phosphate, 

 with barnyard manure, acid phosphate and rock phosphate on the average gave 

 practically the same results, while without manure, acid phosphate was the best. 

 Rock phosphate did not compare so favorably with acid phosphate and basic 

 slag the first year as it did the second and third years. Shallow cultivation 

 gave higher yields of cotton than deep cultivation. 



The influence of kind of soil and fertilization on nitrogen and ash content 

 of crops, .1. G. IMasciihaitpt {Vcrslag. Landbouick. Ondersoelc. Rijkslandbouw- 

 proefsta. [Netherlands], No. 23 (1919), pp. 40-50). — Continuing previous experi- 

 ments (E. S. R., 41, p. 422) with the same soils, crops, and fertilizer treat- 

 ments, the same general results were found regarding the composition of crops. 

 On swamp soil, the potato tubers had a high nitrogen content and a very low 

 phosphoric-acid content. It is concluded that phosphoric-acid fertilizers are 

 not particularly available to crops on drained swamp soil, although the avail- 

 ability was somewhat increased by addition of ammonium sulphate. Marked 

 differences were observed in the composition of crop tops in these experiments 

 from those in previous experiments, especially with reference to potash content. 



It is generally concluded that the influence of fertilization on the composi- 

 tion of the ashes of plants can be judged with safety only when the harvested 

 crops vary very little with reference to yield and growth status. 



Manures in their relation to soils and crop production in the Central Prov- 

 inces, D. Clouston {Agr. Jour. India, 14 {1919), No. 1, pp. 101-106). — This is 



