38 CLOVERS 



when the frost has just left the ground for a short 

 distance below the surface. 



Some kinds of clover are so persistent in their 

 habit of growth that when once in the soil they 

 remain, and therefore do not usually require re- 

 newal. These include the small white, the yellow,' 

 the Japan, burr clover and sweet clover. In soils 

 congenial to these respective varieties, the seeds usu- 

 ally remain in the soil in sufficient quantities to re- 

 stock the land with plants when it is again laid down 

 to grass. Nearly all of these varieties are persistent 

 seed producers ; hence, even though grazed, enough 

 seed is formed to produce another crop of plants. 



Clovers as Soil Improvers. — All things consid- 

 ered, no class of plants grown upon the farm are so 

 beneficent in the influence which they exert upon 

 the land as clovers. They improve it by enriching it ; 

 they improve it mechanically; and they aid plant 

 growth by gathering and assimilating, as it were, 

 food for other plants. 



All clovers have the power of drawing nitrogen 

 from the air and depositing the same in the tuber- 

 cles formed on the roots of the plants. These tuber- 

 cles are small, warty-like substances, which appear 

 during the growing season. They are more com- 

 monly formed on the roots within the cultivable 

 area, and therefore are easily accessible to the roots 

 of the plants which immediately follow. .Clovers 

 are not equally capable of thus drawing nitrogen 

 from the air, nor are the same varieties equally capa- 

 ble of doing this under varying conditions. The 

 relative capabilities of varieties to thus deposit nitro- 



