32 BULLETIN 79, U. S. DEPARTMENT OF AGRICULTURE. 



pounds originally present in the leaf are also removed in the process 

 of curing. In stalk curing, the loss of nitrogen in these forms amounts 

 to 35 to 45 per cent of the total protein and amid and amido nitro- 

 gen, while in curing the picked leaves the direct loss of nitrogen in 

 these forms by the splitting off and escape of ammonia averages 

 less than 10 per cent of the total. In stalk curing, the content of 

 amid and amido nitrogen alone is reduced by about 15 to 60 per 

 cent, depending on the original content of these forms of nitrogen. 

 As regards total nitrogen, the loss in curing the picked leaves is 

 from 4 to 15 per cent of the total, while the loss in stalk curing is 

 from 35 to 42 per cent. 



As regards the organic acids, there is no decided difference in the 

 behavior of oxalic acid in the two methods of curing, and this is 

 true also as to malic acid. Citric acid seems to accumulate to 

 approximately the same extent whether the leaf is attached to the 

 stalk or is detached during the curing. There is no satisfactory 

 evidence that these acids undergo translocation in stalk curing. 



Summing up the more important differences in the results of 

 curing the leaves on the stalk as compared with curing the picked 

 leaves which are brought out in our experiments, it is seen that the 

 loss in weight of dry matter is 10 to 15 per cent greater when the 

 leaves are cured on the stalk. This difference is due mainly to the 

 more complete removal of carbohydrates, including the pentosans, 

 and of protein and, more particularly, to the translocation of the 

 cleavage products of protein and of the mineral constituents from 

 the leaf into the stalk. In stalk curing, in addition to the respira- 

 tion activities which constitute the important factor in curing the 

 picked leaves, the translocation of mobile materials from the leaf 

 into the stalk assumes an important role. This translocation of 

 materials from leaf to stalk in stalk curing constitutes, in fact, the 

 essential difference between this method of curing and that in use 

 after the leaves are removed from the stalk. Our results on this 

 phase of tobacco curing agree closely with the conclusions reached 

 by Mohr from his study of the subject. These results find additional 

 support in the work of Johnson * relating to the composition of two 

 lots of tobacco stalks, from one of which the leaves were removed at 

 the time of harvesting, while the second lot was allowed to cure with 

 the leaves attached. The analyses of the two lots of stalks show 

 that those which were allowed to cure with the leaves attached 

 gained approximately 30 per cent of their original content of total 

 nitrogen, 36 per cent of their content of phosphoric acid, and 8 per 

 cent of their content of potash. This gain in nitrogen, phosphoric 

 acid, and potash can only be accounted for on the assumption that 



1 Johnson, S. W. Analyses of tobacco stalks when cut and after curing. Connecticut Agricultural 

 Experiment Station, 16th Annual Report, 1892, p. 31-34. 1893. 



