304 SOILS 



for several years on the same soil. It is less true 

 of corn smut, onion smut, and ergot, which increase 

 slowly. A change of crops deprives these fungous 

 diseases of the only kind of plants upon which they 

 can feed, so they disappear. Moreover, crops are 

 less vigorous when grown continuously upon the 

 same land, and are therefore more susceptible to 

 disease. 



A number of important insect pests of farm 

 crops may be controlled to a greater or less extent 

 by crop rotation. In general, each crop has its 

 own pests, although insects often feed on more than 

 one kind of plant. Meadows kept for a long time 

 in grass are likely to become infested with the 

 larvae of the May beetle, and with wire worms. 

 A rotation will prevent this. 



Keep the Soil Busy. If but one crop is grown, 

 the soil is usually left bare during part of the year. 

 This is poor farming, except when the land is pur- 

 posely fallowed. No ground should be allowed to 

 remain idle when it might be growing crops, either 

 to sell or to turn under. The busier a soil is kept, 

 provided the right kind of crops are grown, and 

 provision is. made for green-manuring, the more 

 productive it should be. This is more true of 

 Eastern than of Western farming. As land becomes 

 dearer, it becomes increasingly important to keep 

 it busy all the season by means of a well-considered 

 rotation. 



Aside from maintaining or increasing the fer- 

 tility of the soil, a rotation may economise labour. 

 It distributes the labour throughout the year, since 

 crops differ in the time when they are sown and the 

 time it takes to bring them to maturity. This more 

 continuous employment may be exceedingly ad- 

 vantageous, enabling the farmer to secure cheaper 



