HOW LEGUMES HELP THE FARMER 43 



for a few days, and continue to do so as long as they 

 continue to grow. Clover does not, however, enrich the 

 soil with any kind of plant food except nitrates. If we 

 continue to grow clover on the land and to remove the 

 crop every year, the land is likely to become poor in pot- 

 ash and phosphoric acid, unless we add these to the soil. 

 Unleached wood ashes used on clover land would supply 

 all the food materials needed by the common farm crops. 



Other Plants Similar to Clover Clover is not the 

 only plant that yields nitrates from the swellings on its 

 roots. A class of plants called legumes, such as peas, 

 beans, vetches, lentils, and alfalfa, do the same. Crops 

 that add nitrogen to the soil are often called nitrogen 

 gatherers. These crops are very useful to the farmer, be- 

 cause they supply the soil with the most important kind 

 of plant food, and thus, to some extent, they take the 

 place of manure, of which farmers are almost always 

 in need. 



Alfalfa. Alfalfa can be grown in nearly all parts of 

 the country. It is particularly valuable in regions not well 

 supplied with water. The plant lives on from year to year 

 and makes bountiful crops of hay as well as permanent 

 pastures. Swellings or tubercles are found on the roots 

 of this plant as well as on the clover plant, and it enriches 

 the soil in the same way. 



Cowpea. The cowpea is neither a pea nor a bean, 

 but resembles both plants in some ways. This plant is 

 sometimes called the great restorer because it restores the 

 fertility of the soil to a greater extent than any other 

 plant. It is a legume and is especially valuable in the 

 South, where it takes the place of clover. 



