MECHANICAL HARVESTING OF BRIGHT LEAF TOBACCO. PART 16. EFFECTS OF HARVEST SIZE, NUMBER, SCHEDULE, AND METHOD ON YIELD, VALUE, PRICE AND CHEMISTRY(1)
Curing barns and harvesting equipment could be used more effectively, and profits increased, if the harvest could be extended without appreciable decrease in crop values. Also, a very large last harvest, either by priming or stalk cutting, with a low-clearance tractor mounted harvester would be feasible provided crop value was not reduced.
The objective of this research was to measure the effects of harvest size, number, and priming versus stalk cutting on yield, value, price and leaf sugar and alkaloid concentration.
Results were based on 20-plant, replicated field plots conducted during four consecutive years at the Central Crops Research Station near Clayton, N.C. Value and price were determined from plot grade evaluations made by a gov't. tobacco grader and average market price paid for those grades.
Four years of field trials have shown that yield, value, and sugar and alkaloid concentrations were not generally adversely affected by harvesting the leaves as much as one week premature to one or two and sometimes three weeks overripe. However, premature harvesting did decrease the price per unit weight. Value for the plots harvested one week prematurely was maintained by an increase in yield. Also, a four week delay between the first and second primings did not adversely affect yield, value, price or concentrations of sugar and alkaloid. Stalk harvesting and bulk curing of either whole stalks or in combination with priming tended to decrease yield, value and price.
Harvesting the bottom four to six leaves in the first priming followed by the harvest of all of the remaining leaves in a second priming did not significantly reduce yield and value as compared to the four priming optimally harvested check, except when the two-priming sequence involved extremely green or overripe harvesting of the upper leaves. In fact, some of the two-priming schedules had numerically higher yields and values than the check. For example, the bottom priming could be harvested from two weeks green to three weeks overripe without yield or value reductions provided the upper leaves were not harvested extremely green or overripe. If the bottom leaves were harvested one week green to optimum, a four week delay before removal of the upper leaves gave highest yield and value. When the bottom leaves were harvested two weeks overripe, a two week delay before removal of the upper leaves gave the highest yield and value. Harvest of the upper leaves by stalk cutting resulted in a decrease in yield and value.
Many of the two-priming (normal first, large second) schedules resulted in yields and values at least as high as the four priming check. Because of this and the economic and other advantages of a simple tractor-mounted last-over harvester, a change in harvesting philosophy may be justified.
If a large share of upper tobacco (Nicotina tabacum, L.) leaves can be harvested in the last pass through the field some economy could be realized by developing a special machine for that job. Such a machine could be low-clearance and tractor-mounted as the stalks could be broken down by the machine immediately behind the harvest head. The machine could remove leaves in the field or it could cut stalks just below the lowest remaining leaf for stalk curing and later leaf removal.
Bright leaf tobacco has traditionally been harvested in the United States at approximately weekly intervals after whole stalk harvesting (stalk cutting) was abandoned early in this …