WHEAT 113 



clover equivalent to a ton of dry hay will add forty 

 pounds of nitrogen per acre besides that contained 

 in the roots of the clover. 



From Table VII it may be readily determined 

 how much manure or other fertilizer will be neces- 

 sary to use to return to the soil the amounts of 

 plant food removed by a twenty-five bushel wheat 

 crop, and normal yields of other crops used in 

 rotation. 



In a four year rotation of wheat, corn, oats and 

 clover, the supply of organic matter and nitrogen 

 should be maintained by the rotation of clover 

 and by the application of fifteen tons of manure 

 every four years to the clover sod before plowing 

 for corn; or in the case of grain farming without 

 much livestock, the plowing under of one crop 

 of clover with the addition of nine tons of manure 

 per acre will supply the required nitrogen. Fifty 

 pounds of rock phosphate applied with fifteen 

 tons of manure, or one hundred pounds applied 

 with nine tons every fourth year, will maintain 

 the phosphorus content of the soil. 



It is possible to keep up the nitrogen supply 

 without manure by using the rotation with clover, 

 and plowing down the second cutting and adding 

 a catch crop of cowpeas, planted after wheat and 

 plowed under in the fall, preceding corn. This 

 plan would require the use of 250 pounds of phos- 

 phate rock to maintain the phosphorus. If the 

 soil becomes acid or is lacking in lime, it should 

 receive an application of from one to three tons of 

 ground limestone per acre every fourth season. 

 If there is an abundant supply of phosphate in 



