8 FOR BETTER CROPS IN TEE SOUTH 



the form of commercial fertilizers. This makes it by far the 

 most expensive element of plant food that must be added to the 

 soil. There is above each acre of land approximately seventy- 

 five million pounds of nitrogen, as a constituent of the air. If 

 corn is grown in a crop rotation that includes some of the 

 legumes, such as cowpeas, soy beans, clovers, vetches, etc., 

 these legumes take up a portion of this free nitrogen and store 

 it up in such a form that the corn can make use of it, thus dis- 

 pensing with the necessity of buying this expensive element. A 

 crop of cowpeas yielding at the rate of one and one-half tons of 



A heavy growth of soy beans 



dry matter per acre, if turned under will add to each acre of soil 

 sixty-five pounds of nitrogen, or as much as is contained in a 

 forty-five bushel crop of corn. If purchased, this amount of 

 nitrogen will cost the farmer about thirteen dollars. Besides, 

 the organic matter added by the cowpeas is worth more than 

 the nitrogen. 



Southern Soils Need Phosphorus— A very large proportion 

 of southern soils are deficient in phosphorus, especially the soils 

 of a sandy nature. It is not uncommon to find large areas of 

 soils containing less than one hundred and fifty pounds of phos- 

 phorus per acre in the top six inches. Corn cannot be profitably 

 grown on these soils without the addition of some material 

 containing phosphorus. Acid phosphate is the material most 

 commonly used. 



