CHAPTER XVm 



THE FARM ROTATION 



THE rotation of crops is a fundamental 

 practice in good farming operations. The 

 potato is one of the most useful crops in a 

 general rotation, because the clean and thorough 

 cultivation required, as well as the prehminary deep 

 plowing and the digging, puts the soil in excellent 

 mechanical condition. 



The object of rotating crops is to grow a uniform 

 maximum product. All crops benefit by a change. 

 The fertiUty requirements of no two are exactly 

 the same. A soil is benefited both mechanically 

 and in its store of fertility by the changing of crops. 

 For instance, a soil may have plenty of the essen- 

 tial mineral elements of fertility to last for gener- 

 ations, but the amount of those elements available 

 for the use of a certain plant might be exhausted 

 by a few years' continuous cropping. Another crop 

 would require different elements or different 

 amounts or forms of the same elements. By the 

 time the first crop considered would be grown 

 again on this land, the fertility that was exhausted 

 would either be replaced or made available by dif- 

 ferent methods and conditions. On farms where 

 rotation is practised diseases are avoided, checked, 

 or controlled. 



The maintenance and replacing of nitrogen is 

 one of the most important soil cultural conditions. 

 Humus or decayed vegetable matter is a source of 



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