398 TOBACCO LEAF. 



magnesia in the plant is known to be injurious unless 

 lime is also abundant. An average yield of tobacco 

 takes some 30 pounds of magnesia from an acre, and 

 this occurs mostly in the leaf. Yet 1500 pounds of cot- 

 tonhull ashes, the amount usually used per acre, supplies 

 about 165 pounds of magnesia, and less than one-half as 

 much lime. The double sulphate of potash, in equiva- 

 lent quantities, carries about 190 pounds of magnesia. 

 "If too much magnesia is present in the leaf, it may 

 show in the form of the so-called 'light mold' on the 

 leaf when it comes out of the case, greatly damaging its 

 salability, though not materially damaging its qualities 

 for wrappers. This is not a true mold, but is a malate 

 of magnesia an effloresced crystalline matter which has 

 come out of the leaf tissue." Whether this is caused by 

 too much magnesia in the soil or fertilizers is not defi- 

 nitely determined, though such is the belief of some who 

 have given up the use of cottonlmll ashes in consequence. 

 The high grade sulphate of potash, on the other hand, 

 contains little or no magnesia. 



As a substitute for the foregoing articles, this "to- 

 bacco ash constituents" has been prepared, 1000 pounds 

 of it supplying 150 pounds actual potash, phosphoric 

 acid 57 pounds, lime over 200 pounds, ammonia 6 

 pounds, magnesia 20 to 30 pounds. The lime is in the 

 form of a finely powdered carbonate of lime, which is 

 preferred for the reasons fully set forth in Chapter VI. 

 This "tobacco ash constituents" is thus intended to be 

 free from all objectionable characteristics of the sub- 

 stances usually used, and 1000 pounds of it, applied 

 with 2000 pounds cottonseed meal, will be found to 

 supply in liberal excess all the plant food required for an 

 acre of cigar-leaf tobacco, and in thoroughly tested 

 forms. Such a mixture will furnish of ammonia 156 

 pounds, phosphoric acid 77 pounds, and potash 170 

 pounds ; while a crop of 2700 pounds of cured leaf and 



