A FIVE YEAR ROTATION. 143 



larger crops are grown, of course the applications 

 might be increased correspondingly. 



The wisdom of such a rotation must be apparent 

 to every good observer and calculator. The propor- 

 tion of the three substances of plant food in stable 

 manure is so near like that demanded by the five 

 crops of the rotation, that the balance of the soil 

 fertility can be maintained perfectly by the exclu- 

 sive use of such domestic manures. Other grain 

 crops might occasionally be substituted for wheat 



and oats, and root crops for potatoes, 

 "^^cr^pping.' without material change in the 



general result. The gross returns per 

 acre for the five years will be $150 or upward, and 

 it seems that we could well afford to apply thirty 

 tons of yard manure to secure that result. But in 

 case this quantity is not at hand, nor to be had by 

 purchase, what then ? 



In the first place we should use all the yard man- 

 ure that is available for the purpose; and secondly 

 we should supply the deficiency by other means. 

 The one problem that might bother us, is where to 

 get the large amount of nitrogen 1 The article is 

 rather costly, and but scantily supplied in the con- 

 centrated fertilizers usually available for the farmer. 

 In such emergency we may have recourse to green 

 manuring. A crop of clover or peas will help us to 

 draw on the inexhaustible nitrogen supply of the 

 atmosphere, and to transfer the needed quantity to 

 the soil. The minerals are then easily and cheaply 

 supplied in the form of ashes, or of potash salts, 

 and phosphates, etc , as explained in preceding 

 chapter. On the other hand this makes the addition 

 of one year to the five-year period necessary. In 

 that case clover might again be wedged in between 



