EFFECTS OF CROPPING 



33 



Effects of Cropping. When the timber was cleared, or the 

 prairies were broken up, the land was generally productive. After 

 the land has been farmed 40 or 50 years, the productiveness has 

 usually decreased on the average farm, so that not more than one- 

 half the corn or wheat is produced with the same effort. A few 

 farms, that have been well-handled, will still be productive, while, 

 on the other hand, some farms will be so poor that the owners aban- 

 don them. 



FIG. 14. Plowing under rye for green manure. 



The effect of cropping has just reversed the work of nature. (1) 

 By the constant removal of crops, the humus has been exhausted and 

 none returned. As a result, the soil becomes hard, dries out quickly 

 and there is no longer decaying vegetable matter to free new sup- 

 plies of minerals. (2) Sometimes one or more minerals have been 

 exhausted and none returned. (3) The nitrogen is exhausted and 

 no legume grown to return it. (4) The lime is often leached out. 



In most cases, the problem of making this exhausted land pro- 

 ductive again is to change the farm practice, put back what has 



