136 COBN CROPS 



The first class included most of the present Corn Belt 

 States when the land was first broken up. Large crops 

 were grown without soil amendments, but to-day the yield 

 is limited on most of these soils by the lack in available 

 form of one or more mineral elements. 



In the second class, chemical analysis may show the 

 presence of enough minerals and nitrogen for fifty to 

 one hundred crops, and yet the crop be limited, as the 

 minerals may become available only very slowly. This 

 class includes a large share of the above-mentioned soils 

 that have been farmed fifty to one hundred years or more. 

 Decreased availability of minerals may be due to several 

 causes, as deficiency in bases such as lime or magnesium, 

 or more often insufficient organic matter in a state of 

 active decomposition. The addition of lime or organic 

 matter, or both, is the evident remedy in such cases. 



In other cases there is no practical way of making avail- 

 able sufficient mineral elements for maximum crops, and 

 mineral fertilizers must be added. In many soils there 

 are other inhibiting factors to plant growth, even when 

 mineral elements are abundant. This is especially true 

 on poorly drained soils where toxic organic compounds 

 are developed. 



In class 3 are included many of the sandy soils and soils 

 subject to leaching, erosion, or derived from rocks that 

 originally lack some mineral in composition. It is doubt- 

 ful whether corn culture can ever be profitably developed 

 on land of this class. An example is the sandy soil of 

 Long Island, where most of the mineral must be supplied. 

 Often a ton or more per acre of high-grade fertihzer is 

 used. On such land only crops returning a large gross 

 income per acre, as potatoes, cabbage, or truck, can be 

 grown with profit. 



