Dec. 2, 1918 



Greensand as a Source of Potassium 



487 



RESULTS WITH POTASSIUM SALTS 



Culture solutions containing potassium, whether supplied in the 

 form of the common salts or as greensands or marls, were made up on 

 the basis of the number of pounds of potassium supplied to a volume of 

 soil having a surface of i acre and a depth of i foot. In the case of the 

 slowly soluble deposits this gives a measure of direct applicability. For 

 the salt solutions the relation is less usual, but is still a practicable way 

 of calculating concentration. The potassium content in each case was 

 calculated on the quantity known by analysis or formula to be present, 

 solubility not being con^dered. 



In Table II are given data showing the growth made by Turkey Red 

 wheat and red clover in a series of pot sand cultures in which the potassium 

 demand was supplied by the common salts. The concentration of potas- 

 sium in each culture is given in the number of pounds applied per acre- 

 foot. The weights of wheat tops and red-clover tops in an air-dry con- 

 dition are given in other columns. The plants were harvested eight 

 weeks after planting (see Pi. 33). 



Table II. — Results of the growth of wheat and red clover in quartz-sand cultures, with 

 potassium supplied by cotnmon soluble salts 



