364 FORAGE PLANTS AND THEIR CULTURE 



clayey soils than in loams, and better in loams than in 

 sandy soils. Tough clays are, however, very unfavorable, 

 partly on account of their undrained condition. The 

 best growth is secured on fertile clayey soils rich in lime. 

 A good content of humus is also favorable. Deep soils 

 are especially desirable, as this enables the plant to develop 

 its extensive root system which may penetrate to a depth 

 of over five feet. 



Soil moisture conditions are most important for red 

 clover. It will not thrive in sandy or gravelly soils that 

 become droughty. It is especially intolerant of water- 

 logged soil, and on this account is poorly adapted to grow- 

 ing under irrigation on poorly drained lands. 



426. Climatic relations. In a general way the climatic 

 relations of red clover are shown by the map of its dis- 

 tribution, in which both the regions and the extent of 

 its culture are indicated. It is distinctly a crop for 

 humid regions without excessive summer or winter tem- 

 perature. 



No critical studies have been recorded of the cold 

 resistance of red clover, but it is probably more hardy in 

 this respect than alfalfa, as it endures well the winters of 

 Nova Scotia, Maine and Minnesota. Seeds from north- 

 ern-grown plants are preferred for regions of cold winters. 

 Stebler and Schroter remark that dry cold is injurious in 

 Switzerland in spring after growth has begun. 



Regarding the heat tolerance of red clover, the data are 

 even less definite. In the southernmost states the crop 

 succeeds only if planted in the fall, and all of the plants 

 usually disappear by the following August. 



Humidity combined with moderate temperature is 

 favorable to the plant, and dry atmospheric conditions 

 are decidedly unfavorable. Combined with high temper- 



