104 DEPARTMENT OF AGRICULTURE GEORGIA. [390] 



It contains lime 32.56 per cent. 



Sulphuric acid.. ...46.51 " " 



Water 20.93 " " 



100.00 " " 



It is found in extensive beds in different parts of the 

 world, and after being ground to a powder, is much used 

 in old agricultural States as a top dressing for small grain 

 and pastures. 



It constitutes from 40 to 50 per cent, of every commercial 

 superphosphate, in which it occurs as a surplus ingredient, 

 resulting from the treatment of the phosphate of lime with 

 sulphuric acid, and costs the consumer nothing. 



If, therefore, superphosphates are used, there is little ne- 

 cessity for applying gypsum. 



Its beneficial effects have been attributed by some to the 

 sulphur of the sulphuric acid, by others, to the action of 

 the sulphuric acid in fixing ammonia from the atmosphere, 

 and by others still, to the lime, while each probably con- 

 tributes somewhat to the benefit derived from its use. Its 

 action on plants, especially on the legumes, is often very 

 remarkable, but the particular manner in which it acts is 

 not well understood. 



Magnesia is beneficial to some plants and may be defi- 

 cient in some soils, but is generally present in sufficient 

 quantity to supply the needs of our cultivated plants. 



Since kainit is generally employed as a source of potash 

 in commercial fertilizers, a sufficient amount of magnesia 

 is usually incidentally supplied. 



Vegetable fertilizers vary in value with the character of 

 the plants used. 



They constitute the main reliance for the restoration of 

 exhausted lands, and, indeed, may be regarded as an indis- 

 pensable factor in this process. 



They not only restore to the soil, in readily available 

 forms, the mineral elements and nitrogen derived from the 





