108 COTTON CULTURE. 



educated that he can lay off ditches without any level, 

 except on very irregular ground. 



We come now to a consideration of the proper manures 

 for the preservation and restoration of cotton lands, and 

 the best manner of applying them. The harvesting of the 

 product of an acre, for instance, planted in cotton, re- 

 moves from the soil about sixteen hundred pounds of or- 

 ganic matter, of which four hundred pounds is in the form 

 of cotton-wool, or lint, and the balance in cotton seed. 

 No part or constituent of the wool is ever returned. 



Let us now see what chemical substances are abstracted 

 in taking away this wool. Suppose a hundred parts of 

 cotton-wool be burned to an ash, and this ash subjected to 

 chemical tests. What will appear to be its constituents ? 

 Thirty-one per cent., or nearly one-third, is potassa; seven- 

 teen, or less than a fifth, is lime ; and twelve and a half 

 per cent., or just one-eighth, is phosphoric acid ; a little 

 magnesia, and a little sulphuric acid are also found. 



Thus, for every ten thousand pounds of cotton-wool, 

 which might be expected to grow on twenty-five acres, 

 sixty pounds of the above mentioned ingredients are with- 

 drawn from the soil. That is, of phosphoric acid, twelve 

 pounds; of lime, seventeen pounds; and of potassa, 

 thirty-one pounds. Suppose this process to be repeated 

 for twenty years upon the same twenty-five acres. There 

 will have been withdrawn from the soil during that pe- 

 riod two hundred and forty pounds of phosphoric acid, 

 three hundred and fifty pounds of lime, and six hundred 

 and twenty pounds of potassa. Such is the rate at which 

 the wool or staple alone of the cotton exhausts the soil. 

 The consumption is, certainly, very moderate. If a little 

 more than half a ton of these chemical substances were 

 incorporated with the soil every twenty years, or what 

 would be better, sixty pounds a year, the twenty-five acre 

 field would not decrease in fertility. 



Suppose now that the cotton seed as well us the wool is 



