Il6 THE ESSENTIALS OF AGRICULTURE 



the manure is saved and properly used (Fig. 48). The manure 

 contains about one third of the organic matter contained in the 

 crops fed, the remainder being disorganized in the digestive 

 processes of the animal. If we should feed the entire crop 

 grain and straw or fodder to stock and apply the manure, we 

 should lose two thirds of the organic matter, and the supply in 

 the soil could not be maintained. Under average conditions, 

 however, only about half the total weight of the crop produced 

 is fed to animals, the remainder being used as bedding or 

 being left on the ground in the form of stubble or stalks to 

 be worked into the soil. 



144. Live-stock farming and soil fertility. It is possible 

 with a crop rotation of corn, oats, and clover, for instance, 

 where the crops are fed to stock and the manure is returned 

 to the land, to maintain the supplies of nitrogen and organic 

 matter in the soil (Fig. 49). For example, assume an acre-yield 

 of sixty bushels of corn, fifty bushels of oats, and one and one- 

 half tons of clover hay for the first cutting, with a second clover 

 crop of three quarters of a ton. Let us assume, further, that 

 the ear corn is harvested and the cornstalks remain in the 

 field ; that the grain of corn and oats as well as the first crop 

 of clover is fed ; that the oat straw is used as bedding in the 

 feed-sheds and stables ; and that the second crop of clover 

 remains on the land. The gain or loss of plant food on an 

 acre of soil for one round of the rotation may be shown in 

 the tables on page 118. 



It will be observed that there is an actual gain of 45 pounds 

 of nitrogen and a loss of nearly 6 pounds of phosphorus and 

 of almost 10 pounds of potassium. In this estimate no loss of 

 nitrogen is charged to the clover crop, as the nitrogen in the 

 tops, or hay, of clover is about equivalent to that secured from 

 the air. Consequently the nitrogen in the manure from the 

 clover hay, as well as that in the second crop, can be considered 

 as a direct gain to the soil. The nitrogen added by clover should 

 be checked against some losses occurring through nitrogen 

 passing off into the air and by leaching. 



