56 THE HANDBOOK FOR PRACTICAL FARMERS 



Rotations for corn production. — In general the essentials to 

 be included in a good rotation are: (1) A cultivated crop; 

 (2) one or more legumes; (3) a heavy sod forming, grass; 

 (4) deep rooted crops; (5) opiDortunities for catch crops to be 

 used as green manures. With these things in mind every pro- 

 ducer must choose a rotation that best answers his own condi- 

 tions. Some of the standard rotations, including corn, are : 



Many variations of these rotations might be given, especially 

 to include catch crops such as crimson clover, or rye and vetch. 



Barnyard manure. — It was stated under crop rotation that 

 fertility, and consequently crop yield, cannot be maintained by 

 crop rotations alone, but by the addition of legumes, green 

 manures or barnyard manure and mineral fertilizers fertility 

 can be maintained and even increased. The value of organic 

 matter cannot be over emphasized in maintaining fertility, 

 neither can the value of barnyard manure as a source of organic 

 matter. Results from various experiment stations, based on 

 fifteen to twenty-five years' results, show an average value of 

 manure based on the increase in yield of corn alone in the rota- 

 tion to be about $2.50 per ton, and it must be understood that 

 the total value is by no means exhausted by the one corn crop. 

 In fact, it is just as well, and probablj^ better, to apply the 

 manure to the grass and have the residual effect for the corn. 

 By this means the yield of grass is increased and a heavier sod 

 produced to turn under for the corn with a greater total return 

 per ton of manure for the whole rotation. 



Mineral fertilizers. — Mineral fertilizers ordinarily do not pay 

 large returns when used alone on corn as only a part of it is 

 recovered by the crop. It will pay, however, when used in con- 

 nection with a rotation where manure and legumes are employed. 

 Under these conditions it is best to apply the mineral fertilizers 

 to the grain crops, the manure to the sod and plow a heavy sod 



