46 HOW LEGUMES HELP THE FARMER 



soils may be slightly acid and not change blue litmus paper 

 red. Yet lime may be necessary for such soils. To 'find 

 this out, lime should be spread over a small area of the 

 field. If the legumes grow better on the limed piece, lime- 

 stone should be added to the whole field. 



QUESTIONS AND EXERCISES. 



1. What plants bear on their roots little tubercles or 

 nodules which serve as laboratories for the production of 

 nitrates in the soil? What name is given to this group of 

 plants? 



2. Although legumes enrich the soil with nitrogen, they 

 remove what two important plant foods? 



3. What plant foods are contained in wood ashes? 



4. Corn grown on soil that grew clover the preceding 

 year is darker green and more vigorous than corn grown 

 on the same kind of soil that grew timothy the year before. 

 Account for this. 



5. Examine the roots of red clover, sweet clover, alfalfa, 

 peas, beans, and other legumes. Do you find nodules on 

 each? Examine the roots of timothy and other grasses. 

 Do these roots have nodules? 



6. In what ways can we inoculate a soil with the proper 

 bacteria for alfalfa? 



7. Why should the transferred soil or the treated seed be 

 covered in the ground as soon as possible? 



8. How can you tell when a soil is acid? 



9. How can soil acidity be corrected? 



