34 CROPPING SYSTEMS 



been taken out and adopt a cropping system that will restore the land 

 to its original condition. 



Some farms will be found that have remained productive under 

 good farm management and other examples may be found, where 

 unproductive land has been restored by good cropping systems. 



Single Cropping System. When new land has been broken up, 

 the general custom has been at first to grow principally only one or 

 two kinds of exhaustive crops usually the crops that pay best, as 

 corn, wheat, or cotton. In the newer lands of the west (the Dakotas 

 and Canada), we may find the " wheat belt," where wheat has been 

 grown continuously for 20 years. Usually when land has been in 

 one crop for 20 years, it no longer pays and farmers must alternate 

 crops. 



Alternating Crops. East of the wheat belt, where land has 

 been farmed 40 years, farmers have found it necessary to alternate 

 grain and cultivated crops, as wheat and oats with corn. This al- 

 ternate cropping will maintain yield for a time, but the humus, min- 

 erals and nitrogen slowly exhaust, and it then becomes necessary to 

 restore these to maintain the yield. 



Rotation Farming. Coming east to still older farming sections, 

 as Illinois and Indiana, all good farmers have for years been adopt- 

 ing rotation systems, that provide for alternating the cultivated crops 

 and grain crops with clover and grass; the clover and grass to oc- 

 cupy the land from one-fourth to one-half the time. In addition, 

 effort is made to return much of the straw removed with the crops, 

 in the form of manure, while in the early days, little or no manure 

 was returned. A good rotation system will not only restore produc- 

 tivity to much unproductive land, but will maintain it for many 

 years. If in addition to a good rotation, the crop is fed to live stock 

 and the manure returned, the land may be kept up almost in- 

 definitely. 



What the Rotation Does. The rotation of crops (1) main- 

 tains the humus supply; (2) restores nitrogen; (3) alternates 

 crops, having different root systems and habits of growth ; (4) helps 

 control weeds, fungus diseases, and insects. 



( 1 ) If land is continually sown to grain crops, the humus supply 

 of the soil will decrease. Constant stirring of soil causes the oxida- 



