124 BOARD OF AGRICULTUEE. 



A rational system of rotation claims, in this connection, 

 our first attention. 



The crops ought to be selected with a particular view to 

 economizing and accumulating the atmospheric resources of 

 nitrogen. 



Leguminous and other deep-rooting, broad-leafed plants 

 are known to accomplish this object. 



These crops arc, by a natural organization of their leaves, 

 in a superior degree fit to absorb in an advantageous way the 

 nitrogen compounds of the air, and prevent, in consequence 

 of their luxuriant leaf-growth, a wasteful decomposition of 

 the organic matter in the soil by shading it. They send their 

 root to an unusual depth, and turn thus, in part at least, to 

 account that portion of nitrogen which, as nitric acid, has 

 found its way to the subsoil, and is thereby lost to many of 

 our farm-crops, the grain-crops in particular. 



In cultivating, to some extent, deep-rooting plants for feed- 

 ing purposes, we enrich indirectly, in a safe and economical 

 way, the surface-soil at the expense of the subsoil. They in- 

 crease, in consequence of their unusual root-growth, the veg- 

 etable organic matter of the soil, which, as has been shown, 

 is the most reliable form of storing up the nitrogen and other 

 articles of plant-food for succeeding crops ; and improve by 

 their shrinking the mechanical condition of the entire body of 

 the agricultural soil. 



Such results are not surprising, when we consider that the 

 roots of lucern are frequently from twenty to thirty feet 

 long, those of the lupine from seven to eight feet, of the clo- 

 ver from five to six feet, of the beet from six to eight feet, 

 and more. 



Dr. Weiska, of Proskau, who, by careful actual experi- 

 ment, has studied these questions more in detail, states that 

 the nitrogen left upon the soil, in the form of stubble and 

 roots, amounts, in a good average crop per acre, — 



In the case of red clover, to . . . 180 pounds. 



Lupine, to . . . . . . 58 " 



Pease, to ...... . 53 *' 



Buckwheat, to 45 " 



Eye, to 62 " 



