468 INVESTIGATION BY CULTURE EXPERIMENTS 



gan and in northern Illinois, Indiana, and Ohio, sometimes on sand 

 plains and also in sand dunes where the sand has been blown into 

 ridges varying from narrow drifts to extensive sand-hill areas, often 

 covering many square miles, as inTazewell, Mason, and Kankakee 

 counties, in Illinois. 



In composition this soil averages about 1400 pounds of nitrogen, 

 800 of phosphorus, and 31,000 pounds of potassium in the surface 

 6f inches (2^ million pounds). The high percentage of potassium 

 shows that this soil is not a pure quartz sand, but is, to a consider- 

 able extent, of granitic origin. 



In composition this soil is extremely poor in nitrogen, rich in 

 potassium, and fairly well supplied with phosphorus, if we consider 

 its very porous character and the very deep feeding range afforded 

 to plant roots. 



The Green Valley soil experiment field is located on sand-ridge 

 soil in Tazewell County, Illinois. The soil varies from a very sandy 

 loam to a slightly loamy sand that is easily drifted by the wind when 

 not protected by vegetation. This field was broken out of pasture 

 in 1902. In Table 90 are reported results secured in six years from 

 contiguous and comparable plots in that part of the Green Valley 

 field where nitrogen as well as other elements is supplied in commer- 

 cial form. 



TABLE 90. CROP YIELDS IN ILLINOIS SOIL EXPERIMENTS: GREEN VALLEY 



FIELD 



