134 CORN CROPS 



state is the most fundamental problem in production. 

 For cereal culture, the soil must be maintained at the 

 lowest possible cost. The four principal elements to be 

 given attention in most soils are (1) nitrogen, (2) phos- 

 phorus, (3) potash, (4) hme. In addition, active organic 

 matter must be present. 



These conditions are met in the most practical way by : 



(1) A rotation in which legumes furnish a large share of 

 the nitrogen used by other crops in the rotation. 



(2) Where manure is not available, practically all 

 organic matter grown on the land, with the exception of 

 threshed grain, should be plowed under. 



(3) In order to maintain the full supply of organic 

 matter and nitrogen, it may be necessary to plow under the 

 entire legume crop without harvesting. 



(4) Where live stock is kept, all manure made by feeding 

 produce should be returned to the land in relatively light 

 dressings. 



(5) The constant removal of grain will gradually reduce 

 the phosphorus and potassium. This must be returned 

 as commerical fertilizer. A part at least can be mixed 

 with the manure and applied in this way. 



(6) Where fertilizer mixtures are applied to land, careful 

 regard should be given to the needs of the land, and the 

 fertilizer should be mixed to meet the particular needs in 

 each case. 



(7) Where lime is required, it should be applied once 

 every four to six years, the amount being determined by 

 the needs of the land. 



