COTTON CULTURE. 129 



a substitution of magnesia for lime. The amount of pot- 

 ash is very nearly the same in both varieties. The Sea 

 Island has a little more phosphoric acid than the other, 

 and less lime. The soil upon which the two hundred 

 pounds of cotton, thus analyzed, was raised, was found to 

 be composed, as to its bulk, of nine-tenths of fine alluvial 

 sand, and one-tenth of a cement, consisting of sand, perox- 

 ide of iron, clay, lime, magnesia, and humus. 



An examination of the cement, or that part of the soil 

 which is not entirely sand, shows that it is composed very 

 largely of a combination of sand and peroxide of iron, a 

 considerable amount of magnesia, and a small quantity of 

 lime. On account of the deficiency of lime, the cotton 

 plants are led to appropriate more abundantly magnesia, 

 a substance which, in its chemical character and proper- 

 ties, much resembles lime, and which, therefore, is capa- 

 ble of taking its place to some extent. 



As to the directly nourishing properties of the soil, the 

 analysis shows, that in the three thousand tons which 

 constitute the surface for the depth of one foot over an 

 acre, there is less than fifteen pounds of phosphoric acid. 

 As one two-hundred pound crop consumes nearly nine 

 pounds of phosphoric acid, it follows that, with no ma- 

 nure, the second crop, planted on the same soil, would 

 find a little more than half enough phosphorus for its 

 proper growth. 



In the same soil, there was found less than twenty 

 pounds of potash, so that, as a two-hundred pound crop 

 consumes over nine pounds_of this chemical salt, the third 

 successive crop, without manure, would find little or no 

 potash to feed upon. The result of this chemical exami- 

 nation of the Sea Island soil is, that it must be kept up by 

 the use of manures rich in the phosphates, rich in potash, 

 and having a considerable amount of sulphuric acid. A 

 dressing, composed of rotten cotton seed, mixed with the 

 ordure of domestic animals, if used in sufficient quantities, 

 6* 



