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



CURING THE LEAVES ON THE STALK COMPARED WITH CURING THE 



PICKED LEAVES. 



The relative merits of tlie two methods of curing have long been 

 a subject of interest to agricultural investigators, both in this and 

 in foreign countries, and the greater portion of the experimental 

 work relating to tobacco curing which has been done has had special 

 reference to this problem. Some of the earlier investigators main- 

 tained that the leaf weighed more when cured on the stalk, because of 

 a flow of soluble material from the stalk into the leaf. Others, how- 

 ever, notably Nessler 1 and Behrens, 2 maintained that there was no 

 particular difference in results as between the two methods of har- 

 vesting and curing, either with reference to weight or to quality of 

 the cured leaf. We are indebted to Mohr 3 for the first comprehensive 

 and decisive study of the subject. Mohr brought out clearly the 

 errors in the methods of procedure and in the interpretation of results 

 made by previous investigators and proved beyond doubt that for 

 the particular type of tobacco with which he worked (cigar-wrapper 

 leaf) the leaf cured on the stalk loses in weight approximately 11 or 

 12 per cent more than if cured after being picked from the stalk. 

 This is equivalent to saying that a picked leaf after curing will weigh 

 11 or 12 per cent more than would the same leaf if cured on the stalk. 

 Mohr proved conclusively by analyses of the ash and other con- 

 stituents that the increased loss in weight which occurs when the 

 leaf is cured on the stalk is due not so much to a more intense respira- 

 tion but rather to a translocation of nutritive material from the leaf 

 into the stalk. 



Coming to our own experiments, by reference to Table I (p. 5) it 

 is seen that with comparable material harvested and cured by the 

 two methods in question during the years 1908, 1909, and 1910 the 

 losses in dry weight by curing the leaves on the stalk were 12.2, 18.9, 

 and 10 per cent, respectively, greater than the losses in curing the 

 picked leaves. The larger indicated difference in loss of weight 

 between the two methods for 1909 is to a great* extent due to the 

 unusually small loss in weight of the picked leaves, and this in turn 

 is fully explained by the abnormally low content of starch of the 

 picked leaves at the time of harvesting. However, the average dif- 

 ference between the losses in weight for the three years by the two 

 methods of harvesting and curing is 13.7 per cent, taking the figures 

 as they stand; and this value is in close agreement with Mohr's results 

 for the same general type of tobacco, namely, cigar-wrapper leaf. 

 On the other hand, Table II (p. 8) shows that the difference in loss 



i Nessler, J. Der Tabak, seine Bestandtheile und seine Behandlung, Mannheim, 1867. 



2 Behrens, Johannes. Weitere Beitrage zur Kenntnis der Tabakpflanze. Die Landwirtschaftlichen 

 Versuchs-Stationen, Bd. 43, p. 280, 1894. 



' Mohr, E. C J. Gepfliickter und am Stamme getrockneter Tabak. Die Landwirtschaftlichen Versuchs- 

 Stationen, Bd. 59, Heft 3/4, p. 253-292, 1903. 



