208 THE ESSENTIALS OF AGRICULTURE 



may prevent a stand. The bacteria of clover tubercles do not 

 thrive in a soil that is acid. The best results with bacteria are 

 obtained if the soil is slightly alkaline. The results of recent 

 investigations show that probably half the soils in the clover- 

 growing region are either acid or neutral. To correct this 

 condition, lime is being extensively used. It is usually not 

 necessary to inoculate the soil with bacteria when sowing clover, 

 but it is desirable to do so on soils that have become acid. 



269. The choice of a nurse crop. The practice of sowing 

 clover and similar seeds with a nurse crop is almost universal, 



FIG. 97. A field of red clover ready to be cut for hay 



but not always commendable. Winter wheat is the best nurse 

 crop to use, because the wheat is harvested early in the season 

 and does not smother the young clover plants or exhaust the 

 moisture to the same extent as other crops. Barley makes an 

 excellent nurse crop. Oats, used perhaps more generally for 

 this purpose than any other cereal, is a poor nurse crop, be- 

 cause it requires a large amount of moisture for its own growth, 

 produces a dense foliage which smothers the young clover 

 plants, and is harvested late in the season when the rainfall is 

 low and when the sunlight and heat are intense. When oats is 

 used as a nurse crop the rate of seeding of the oats should be 



