228 SYSTEMS OF PERMANENT AGRICULTURE 



shall also be returned to the land after threshing out the grain or 

 seed, and that the regular crop of clover shall be mowed and left 

 lying on the land. If necessary, to prevent too rank a growth 

 (which might smother the plants), the clover may be mowed twice 

 before the seed crop is allowed to grow. 



If the larger yields are considered, the same rotations hold, ex- 

 cept that the richer soil would very possibly furnish a larger pro- 

 portion of the nitrogen required by the clover plant. 



With some modifications, these two three-year rotations may be 

 combined in a six-year rotation of (i) corn, (2) corn, (3) oats, 

 (4) clover, (5) wheat, and (6) clover, which avoids the necessity 

 of seeding wheat on the corn ground, a task sometimes difficult 

 to accomplish. If necessary, this may be reduced to a five-year 

 rotation, either by omitting one corn crop, or by plowing under the 

 clover in the spring of the fifth year as late as practicable for corn. 

 With the former change it will be less difficult, and with the latter 

 more difficult, to maintain the nitrogen, than with the six-year 

 rotation. 



A four-year rotation, which the author prefers for the general 

 conditions in the North Central states, includes the four crops, 

 wheat, corn, oats (or barley), and clover, in the order given. 

 Clover should also be seeded on the young wheat in the early spring, 

 and plowed under (after disking, if necessary to insure capillary 

 connection) as late as practicable the next spring before planting 

 corn. In grain farming only the seed crop of clover is removed 

 from the land, and the phosphate is plowed under with the clover 

 residues for the wheat. All of the threshed straw (from wheat, 

 oats, and clover) is hauled from the threshing directly to the field, 

 where it may be thrown off in windrows, and soon afterward spread 

 over the land as uniformly as necessary. It may be used for a top 

 dressing for wheat, or it may be applied in moderate amounts to 

 the land from which wheat has been harvested, where the young 

 clover is growing as a green manure for the following corn crop. 

 Judgment must always be exercised in the matter of applying 

 large amounts of straw, or of plowing under heavy crops, or applica- 

 tions of coarse material, which may do damage if turned under 

 too late in the spring, especially if the season is dry or if the soil is 

 deficient in lime. 



