1919] SOILS — FERTILIZERS. 423 



the farms as good and ordinary, the results for all tests Bhowed average yields 

 of 30.1 bu. per acre without nitrate and 39.4 bu. with nitrate on the former, as 



compared with 20.8 bu. without nitrate and 27.5 bu. with nitrate on the latter. 



Experiments on the value of greensand as a source of potassium for plant 

 culture, it. II. Tbtte and F. \v. Geise {Jour. Agr. Research \r. g.], t5 {1918), 

 No. 9, pp. 488-492, pis. 2). — In the experiments described In this article, a con- 

 tribution from the Bureau of Planl industry of the D. S. Department of Agri- 

 culture, the availability of the potash in samples of greensand and greensand 

 marl from New Jersey and Virginia, containing from \J>2 to 7.63 per cent of 

 total potash, was studied In pot experiments with wheat and red clover, com- 

 parative tests being also made with other forms of potash. 



The conclusions reached were that, as shown by pot experiments carried 

 out with crushed quartz and Shive's culture solution as a basis, "greensands 

 and greensand marls from Virginia and New Jersey are able to supply sufficient 

 potassium to satisfy the demand of Turkey red wheat and red clover during the 

 first two months of their growth. This enables them to make a greater dry 

 weight of tops than was seen in similar cultures in which the potassium demand 

 was supplied by potassium chlorid, potassium sulphate, and potassium phos- 

 phate. The prompt availability of sufficient potassium to meet the needs of 

 many, perhaps most, farm crops seems to be indicated." 



Limestone action on acid soils, R. Stewart and F. A. Wyatt (Illinois Sta. 

 Bui. 212 (1910), pp. 266-296, fig. 1).— Experimental work begun in 1902 on the 

 Odin experiment field in Marion County and in 1912 on the Newton field 

 in Jasper County Is described, in which observations have been made upon the 

 effect of limestone on the surface soil, loss through drainage, the influence of 

 applications of limestone to surface soil upon acidity in the subsurface and sub- 

 soil, the relative value of high-calcium and dolomitic limestone, the effect of 

 the degree of fineness upon loss and upon acidity, and the comparative effect 

 and loss of light and heavy applications. Considerable tabular data are pre- 

 sented and fully discussed showing the rates and form of lime applied to the 

 various plats, and giving information relative to the amount of residual lime- 

 stone and degree of soil acidity found and destroyed with the different treat- 

 ments. Based on the evidence secured, the following conclusions with regard 

 to the common prairie land of southern Illinois are deemed justified. 



An application of one ton of limestone per acre once in three or four years is 

 sufficient to keep the soil alkaline, after the initial acidity has been destroyed 

 by heavier applications. Dolomitic limestone can be used successfully on acid 

 soils, being slightly more effective than high-calcium limestone in neutralizing 

 soil acidity, being more durable, and having no injurious effects on crop yields. 



Results obtained on the Newton field failed to show that finely ground lime- 

 stone was more effective in correcting soil acidity than was the total product 

 from a i-in. screen, which contained both the finer material for immediate use 

 and the coarser material for greater durability. It is stated that this "mill- 

 run" product appeared to be the most economical form to use, although final 

 conclusions must await further data concerning crop yields. 



On the Odin field after fourteen years one-half the acidity in the subsurface 

 soil was neutralized where the larger applications had been made to the sur- 

 face, and one-fourth where the lighter applications had been made, while appli- 

 cations of limestone to the surface soil seemed to have no effect upon the acidity 

 of the subsoil. The amount of native limestone found in the subsoil was a vari- 

 able quantity, none being present in some cases, even at a depth of 40 in., 

 while in other cases it extended upward even slightly into the subsurface soil. 

 112S74°— 19 3 



