342 IRRIGATION FARMING. 



tion, probably not more than half the amount that is 

 given to the hay crop. 



Fertilizing Elements. — Plowing under green 

 alfalfa as a manurial agent and soil restorative is be- 

 coming recognized in the west as a very essential 

 agency in preventing soil deterioration. It is there- 

 fore a very useful plant in following out a line of crop 

 rotation. As a green manure or soil renovator, alfalfa 

 is hardly equaled by any other plant. It is very rich 

 in phosphoric acid, potash, and lime, and gets a goodly 

 portion of nitrogen from the air, leaving much of this 

 in the soil by means of its large roots Aside from 

 this, when used as a green manure there is a great deal 

 of humus added to the soil, both by the matter turned 

 under and by the roots. The large, long roots open 

 the subsoil to a great depth, serving much the same 

 purpose as the subsoil plow. The writer once saw an 

 alfalfa root at Las Vegas, New Mexico, that measured 

 thirty-two feet in length and had been secured by some 

 laborers while digging a well in an old alfalfa patch. 

 When once well rooted a stand of alfalfa seems as im- 

 pregnable as the gates of Hercules, but a stout and 

 sharp sward-plow and four draft-horses will turn down 

 the growth at the rate of two or three acres a day if 

 properly handled. 



The extraordinary demand made upon available 

 plant-food in the soil by a crop of alfalfa is something 

 not fully comprehended by all growers of the great 

 legume. These demands are especially noticeable in 

 the Ease of nitrogen and potash, crops often collecfting 

 over one-quarter of a ton of each from an acre in a 

 season. It is universally admitted that the mineral 



