AND AGRICULTURE. 49 



not artificially supplied, the best land will soon 

 become poor. Each crop robs the soil of a cer- 

 tain quantity of its substance ; and, of course, if 

 the farmer annually takes away these substances 

 from his land in his crops, and never makes good 

 the loss by new additions, he must expect his 

 farm soon to be run out. 



By the addition of manures containing the 

 substances the crop takes from the soil, its pro- 

 ductiveness may be made permanent. Manures 

 should be supplied of the right kind, in appro- 

 priate quantities, and at the proper periods of 

 the year ; and there should always be more in 

 quantity of the substances taken up by the crops, 

 than they annually consume. 



Many farmers are afraid of the cost of ma- 

 nures, and so they always have unproductive 

 land and unprofitable crops. Others supply an 

 abundance of manure, but it often is not the 

 kind the land needs, and is just so much waste : 

 whilst others render the manure they do use of 



Questions. Why does the removal of crops from the 

 land impoverish it ? How may the productiveness of land 

 be maintained ? What kind of manures should be used ? 

 Should the manures contain more of a given substance than 

 the crop consumes ? 



5 



