CHAPTER XI 



POOR CROPS AND HOW TO GET BETTER ONES 



GOOD crops are sometimes grown for a number of 

 years, and then the crops become poor even when they 

 have been well cultivated and given all the water they 

 needed. If they are free from insect and fungous 

 pests, the fault must lie in some condition in the soil 

 itself. To get good crops again we must first know 

 the cause of the trouble, and then remove it. 



One of the commonest causes of poor crops is growing 

 the same crop on the land year after year. Thejroots 

 then take out the same substances from the soil in the 

 same places every year. It is like using a grindstone 

 in one place only, making a groove that spoils it for 

 general use. The same crop should therefore never be 

 planted more than twice in successive years. It is 

 better to change the crop every year, selecting such as 

 have very different kinds of roots (see pages 11, 287), 

 and which take different proportions of food substances 

 from the soil. This plan is called rotation of crops. 



Rotation of crops. A grass or grain crop with crown 

 roots should be followed next year by a root crop such as 



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