BOTATION OF CROPS. 87 



grasses, or clover, which continue to grow from early 

 spring until late autumn,can make use of more nitrogen 

 than those which finish their growth in early summer, 

 , as wheat. Indian corn, in this respect, has a great 

 advantage over the small grains. It makes much of 

 its growth after wheat has fully matured. It is thus 

 able to make use of the supplies of available nitrogen 

 which are being formed during the summer. Still 

 more is this true of grass or clover, which continue to 

 grow still later in the season. 



It seems reasonable to believe that plants which 

 have a long season of growth can thrive fairly well on 

 soils with a less supply of available plant food of any 

 kind than can those which make their growth in a 

 short time. 



In soils with loose, open subsoils or where manure 

 with much nitrogen has been applied, especially in 

 regions where there is considerable rain in the autumn 

 and early spring, there is good reason for following 

 early ripening crops with some fall-growing crops, as 

 wheat or rye, or for seeding the land with clover or 

 grass. 



Green Manuring. — One form of rotation of crops 

 which is often highly recommended is the growth of 

 crops with sole reference to their manurial value. In 

 this country, sowing a crop of clover or buckwheat, or 

 of cow peas in the Southern States, in the spring, or of 

 rye in the fall, and plowing the crop under when it 

 has made a good growth, are the most common 

 methods of green manuring. The effects are often 

 very noticeable. The store of vegetable matter in the 

 soil is largely increased. Sometimes this much im- 

 proves the physical condition of the soil. Always the 



