ROTATION 377 



ADVANTAGES OF ROTATION 



1. Better Distribution of Work. The one-crop system throws 

 a large amount of work at about the same time so that a large 

 force of men and horses are necessary to plant, cultivate or harvest 

 the crop. The most economical use of time and labor is accom- 

 plished when it is more uniformly distributed throughout the year. 

 In a rotation the several crops are planted at different times. They 

 mature so as to distribute the work of harvesting over a considerable 

 period. This helps solve the farmer's labor problems by furnishing 

 more permanent employment to the laborer. 



2. Control of Insects and Plant Diseases. A very serious 

 objection to any one-crop system is the encouragement it gives to 

 injurious insects that prey upon the crop. This is especially true 

 of corn. The corn root aphis and the corn root worm become very 

 serious pests where this crop is grown very long in succession. 

 Growing some other crop for several years destroys many of these. 

 The same is true of plant diseases such as flax wilt, cowpea wilt, 

 clover sickness, potato scab, dry rot of corn, etc. These are worse 

 than the insects. They may be completely controlled by rotation, 

 since in this case the particular host plant upon which each lives 

 will not be present every year, thus creating conditions very un- 

 favorable for their survival. 



3. Control of Weeds. Many crops have their particular weed 

 or weeds that are in some way favored by them. Many weeds 

 favored by one crop will be smothered by another. Cultivation 

 of one crop may be the means of destroying some, while others may 

 be killed by pasturing or by a tough, heavy sod. 



One-crop systems tend to encourage many kinds of weeds. At 

 Hothamsted, England, on the plots where wheat had been grown 

 continuously for many years the ground became so foul that fallow- 

 ing had to be practiced occasionally to eradicate the weeds. Corn 

 cockle and chess growing with wheat are familiar examples in this 

 country. Kemove these from their association with wheat and they 

 are easily killed. Old pastures sometimes become so full of weeds 

 that the grass amounts to little. Ox-eye daisy, yarrow, verbena, and 

 iron weed sometimes take pastures. Hence it becomes as necessary 

 to rotate pastures as any other crop unless great care is taken to 

 keep these enemies out. Pastures and meadows may be kept clean, 

 as seen in England, where the grass fields are several decades old. 



