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LEGUMES 



The legume forage and seeds are very high in protein content. 

 The seeds of grass plants (maize) are high in starch. Certain 

 legumes store considerable oil, as illustrated by the soy bean. The 

 seed of grasses has a large endosperm, usually rich in starch, and a 

 small embryo, while in legume seeds there is no endosperm, but the 

 seed is filled with embryo. The composition of legume seeds is 

 about the same as that of the embryo of grass seeds. 



Effect of Legumes and Grass on Fertility of Soil. It has 

 already been pointed out in Chapter V, on Rotation of Crops, that 

 both grass and legumes, in a rotation with grain crops, help to main- 

 tain productivity as compared with grain alone. Rotation, how- 

 ever, is not a permanent means of restoring productivity, as both 

 grass and legumes exhaust the mineral supplies of the soil. In one 

 important respect they differ, and that is the effect on nitrogen 

 supply of the soil. Legumes acquire free nitrogen from the air, and 

 it is fair to suppose that they do not exhaust this element, the most 

 costly of all, from the soil. 



The principal method of determining this point in field tests is 

 to grow crops of legumes and make occasional soils analysis, or to 

 grow legumes, alternating with grain crops, noting the general vigor 

 and appearance of the crops. In certain rotation experiments, 

 where red clover has been grown one year in three or four, the 

 nitrogen supply of the soil has been maintained, although the grain 

 crops would remove large amounts. 



One way of comparing the relative exhaustive effect of legumes 

 and grasses is to evaluate the important fertilizing constituents. 



