SOIL EXHAUSTION AND ROTATION OF CROPS. JQj 



agriculture we usually have a large quantity of pasture and keep 

 a good many cattle, for we have to depend largely on their manure. 

 We have to sell off' a large share of the crops, which remove valu- 

 able materials from the soil, and we cannot or do not buy fertilizers 

 to make good the deficiency. In the other case, the farmer can 

 put in as many fertilizers as he chooses to pay for. lie is able to 

 buy them, and he finds his profit in using them. In "extensive" 

 agriculture, which is made necessary by circumstances, the farmer 

 must depend largely upon rotation ; he must bring it into success- 

 ful use. As he succeeds or f.iils to do this he carries on a paying 

 or a losing business. In "intensive" agriculture the farmer is 

 largely independent of this necessity ; he can rotate or not, very 

 much as he chooses. Rotation is not indispensable to his success. 

 That is, the advantages that come from rotation are not so great 

 as the other advantages which the farmer has at command by the 

 use of plenty of money, plenty of fertilizers, by his nearness to 

 market, and high prices. 



Now, I wish to state some of those principles which should 

 govern us in .rotation, so far as this depends on what we may call 

 the chemistry of the crop and the soil. So far as the feeding 

 power of the soil is concerned, the special requirements of the 

 crop should determine the rotation. Of course there are other 

 conditions to be taken into account in practice. Winter wheat, 

 for example, cannot follow itself beyond a certain length of time, 

 even if the soil will allow, because the land ordinarily becomes 

 foul' with weeds ; and it is better to alternate with some crop 

 which will enable us to destroy the weeds by hoeing or which will 

 choke them out directly. There are many conditions which influ- 

 ence rotation that I do not propose to speak of, but I shall confine 

 myself to that part of the subject which is involved in the feeding 

 of the plant. The broadest principle of rotation is to alternate 

 grain crops and forage crops. That is, to follow plants having 

 a short and rapid growth and which produce seed, by plants of a 

 longer period of growth which are not allowed to ripen seed, but 

 are harvested for their large amount of foliage. 



Plants, like animals, have different ways of feeding. If yon 

 were to undertake to keep a dairy of hyenas you would have .to 

 provide a different food from that which you give to cows. If 

 you should choose the giraffe as a domestic animal you would find 

 that its habits of feeding are adapted to very different circum- 

 stances from those of your common pastures. The natural food 



