MIXTURES FOR CROPS 



Maintaining Fertility. A heavy clover sod 

 gives assurance that a good crop of corn or potatoes 

 can be grown. If the amount of plant-food in 

 the sod is not excessive, a heavy crop of wheat can 

 be produced. The condition of the soil favors 

 many crops. The clover has placed it upon a pro- 

 ductive basis for the time being. 



The object that should be kept in view, when a 

 scheme of soil fertilization is worked out, is the 

 maintenance of such a state of fertility that the 

 land can be depended upon for whatever crop 

 comes round in the rotation. When a 3-10-6 

 fertilizer, or a 3-8-10 fertilizer, is used, the effect 

 upon a thin soil is to restore it temporarily to this 

 good-cropping power, the size of the application 

 varying with the crop. A richer soil may want 

 the phosphoric acid and potash without the nitro- 

 gen. A manured soil may need only the phos- 

 phoric acid. The purpose of the fertilizer in any 

 case is maintenance or increase of fertility, and 

 when this object has been secured, the crop 

 may be whatever the rotation calls for. It is 

 this rational scheme that gives success to the 

 Pennsylvania station's methods on some of its 

 test plats. A given amount of plant-food is put 

 upon the land, which is under a four years' rota- 



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