CLASSIFICATION OF FORAGE CROPS. 19 



Some plants, which are normally annuals, are sown in the autumn, 

 and after making a growth of foliage that season, lie more or less 

 dormant during the winter and resume growth the following spring, 

 reaching maturity in the early summer. This is true of rye, some 

 varieties of wheat, and some of the grasses. The severity of the 

 winter determines in many cases whether plants may be used in this 

 ww. Many crops that are spring sown in the Northern States are 

 fall sown in the South. Furthermore, some plants can be made to 

 live for an abnormally long period by frequent mowing, thus pre- 

 venting the production of seed. 



NATURAL GROUPS. 



Legumes. — This important group of plants includes the clovers, 

 alfalfa, the cowpea, soy bean, the vetches, the garden beans and peas, 

 and all similar plants, and it derives its importance from the fact that 

 both the seeds and the foliage are richer in nitrogen than other forage 

 plants. Since the proteids, or nitrogen-containing materials, are the 

 most expensive portion of feeding rations, the growing of legumes for 

 forage has long been recognized as an important factor in the economy 

 of agriculture. But furthermore, as is well known, the legumes have 

 the power, not possessed by other forage plants, of utilizing the free 

 nitrogen of the air by means of the nodules on their roots. (See PI. II.) 

 When legumes are turned under as green manure, or even if the tops are 

 removed by mowing and the roots allowed to remain in the soil, the 

 nitrogen content of the latter is increased. Since nitrogen is a very 

 essential plant food, and is one of the first to be exhausted in soils upon 

 which crops are grown, and since this element is the most expensive 

 to add in the form of fertilizer, the importance of growing legumes in 

 rotation with other crops for the purpose of renovating the soil is quite 

 evident. These facts emphasize the necessity of adopting a system of 

 agriculture for a given region which shall include the growing of 

 suitable crops of legumes in the rotation, thus utilizing the crop as for- 

 age and at the same time keeping up the fertility of the soil. The 

 leguminous forage crops adapted to Nebraska are alfalfa and red clover, 

 which are perennials, the latter usualty short lived, and cowpeas and 

 soy beans, which are annuals. In addition to these, white clover and 

 alsike clover are occasionally used. 



Grasses. — The great bulk of the forage plants, not included in the 

 above group of legumes, belongs to the natural group of plants known 

 as grasses, which includes besides the common meadow and pasture 

 grasses, both wild and cultivated, such plants as the grains or cereals, 

 sorghum, millet, and the sugar cane of the South. The grasses do not 

 have the power of adding nitrogen to the soil after the manner of the 

 legumes. Most of our native grasses are perennials, as are also our 



