CROP ROTATION 213 



but in doing this he often loses sight of the future. He 

 may reason thus: "If corn is a high price and my 

 soil will raise good corn, then corn is the crop for me 

 to raise." So year after year he raises corn on the 

 same fields until he finds that his soil will not raise a 

 good crop of corn. The cause is not far to seek. Corn 

 requires the same kind of plant food year after year, 

 and unless this food is restored in some way, the soil 

 becomes exhausted of some of its fertility. So the farmer 

 needs to consider, not only the returns he will get from 

 his crop this year, but the effect that the crop will have 

 upon the soil. 



Cover crops. On all sloping lands, if neglected, the 

 soil may wash into gullies, and in a few years a fer- 

 tile field may be completely ruined. Such lands should 

 i)e kept in grass as much as possible, and when such 

 lands are cropped, the rows should run lengthwise the 

 hill and not up and down the slope, thus checking the 

 tendency to wash. One of the best means of preventing 

 washing of the soil is to plant a crop in the fall that 

 will cover the ground thickly before freezing weather, 

 and thus not only hold the soil, but prevent its being 

 packed by the rain. Such crops are called cover crops. 

 Rye or the clovers are especially used for this purpose. 



A system of crop rotation. Crop rotation consists 

 in growing one kind of crop on the ground this year, 

 another kind of crop requiring different plant foods the 

 next year, still another the year following, and so on, 

 the crops following each other in succession, and at regu- 

 lar intervals. For example, our field number 2 (see 



