94 DEPARMENT OF AGRICULTURE GEORGIA. [380] 



removal of a single necessary mineral element, the absence 

 of which renders unavailable the others, though present in 

 abundance. Fortunately for man, howevei, nearly all of 

 the mineral elements exist in practically inexhaustible 

 supply, so that even on the most worn soil;, only a few of 

 these elements need be artificially supplied and these are 

 readily accessible. 



Phosphoric acid is, as regards the necessity of artificial 

 supply, first in importance, potash second, and lime, per 

 haps, third ; other elements being required in very small 

 quantities for general vegetation. 



Generally phosphoric acid and potash, of the inorganic 

 or mineral elements, and nitrogen, of the organic, are all 

 that need be supplied by the farmer to secure remunera 

 tive crops, even from worn soils, if a judicious system of 

 rotation of crops, involving a liberal return of vegetable 

 matter from legumes, to the soil, is practiced. 



If all the vegetation annually produced upon the land 

 was returned to it. the soil would annually increase in fer- 

 tility. If, however, as is usual, a part of the crop is annu- 

 ally removed, mineral substances equivalent to those con- 

 tained in the portion of the crops carried off must be re- 

 turned to the land to maintain its normal fertility. 



The roots of all plants, and especially those of the legumes, 

 have a power of acting chemically upon the mineral com- 

 pounds of the soil in such manner as to render a portion of 

 them available as plant-food. To this power, in part, is 

 attributed the beneficial effects of the cultivation of the 

 legumes, peas, clover, etc. 



The following list shows the amount of mineral ingredi- 

 ents withdrawn from the soil by different crops. It is taken 

 from Prof. Pendleton's " Scientific Agriculture," and is 

 worthy of careful study by farmers : 



A crop of 750 pounds of seed cotton will carry off from 

 an acre of land 23.25 pounds'of nitrogen, and 33.3 pounds 



