SUMMARY. 25 



the sulphate greatly increase the quantity of sulphuric acid in the 

 ash. The carbonate would seem to be an ideal form in which to 

 supply the potash for combinino; Avith the organic acids in the plant, 

 and its use has generally been found to improve the burning quali- 

 ties. But, aside from the high cost of this material, there are other 

 serious objections to its use, for it has a very strong alkaline reaction, 

 and it seems i)robable that when used in large quantities it will 

 eventually injure seriously the productivene^ss of the soil. The sili- 

 cate is free from these objectionable properties, and if the potash 

 can be made available there is every reason to believe that this will 

 ])rove to be a very valuable source of potash for tobacco. 



The sum of the lime and the magnCvsia in tobacco does not, as a 

 rule, vary widely ; or, in other words, the greater the amount of lime 

 the less will be the amount of magnesia, and vice versa. The appli- 

 cation of fertilizers containing magnesia increases the percentage of 

 this element in the tobacco, but when used in the form of the car- 

 bonate the injury to the burning qualities w'ould be reduced to a 

 minimum. It is believed, however, that the use of fertilizer salts 

 containing magnesia in the form of sulphate is inadvisable. 



The percentage of organic nitrogenous compounds, including nico- 

 tine, is generally proportional to the luxuriance and vigor of growth ; 

 hence tobacco of very rank growth contains excessive quantities of 

 these constituents. Again, these substances are most abundant when 

 the plant is, as a whole, growing most rapidly, and also in the most 

 rapidly growing parts of the plant. Conditions favorable to rank 

 growth are brought about by the use of excessive quantities of nitroge- 

 nous fertilizers, especially when the nitrogen is in readily available 

 forms. The chief danger from this source, however, lies in the appli- 

 cation of quickly available forms of nitrogen during the later stages 

 of grow^th, thus preventing or delaying the normal ripening of the 

 leaf. Since the percentage of albuminoids decreases rapidly through- 

 out the ripening process after the leaf has reached its full growth, 

 this is an important reason wdiy tobacco should not be harvested 

 until the leaf is well ripened. 



105 



