Harvester Operations Harvesting is a compromise between losses and damage to the grain. Damage can include reducing head rice by cracking or crushing kernels, shelling kernels and unacceptable dockage through inadequate cleaning. Most adjustments in the operator's manual that comes with the combine deal with reducing losses first, which is appropriate because losses are usually worth more than quality unless there is an unusually large amount of damage. This suggests growers are doing a good job of adjusting combines to minimize losses. After losses are minimized, reduction in grain damage is pursued primarily by reducing the cylinder speed and opening the concave clearance.
Combines require settings unique to the crop, variety and maturity.
Most harvester manuals give initial settings for the crop, but you must be prepared to adjust these based on conditions in a given field and the threshing characteristics of the particular variety. These initial settings are reasonable for long grains, which are usually drier and less rank at harvest. Generally, the reduction in head rice was offset by the increase in recovery as cylinder speed increased. In comparison tests of rasp and spike tooth cylinder, the rasp bar was gentler and produced slightly higher milling yields, but had greater losses, which offset the head rice gains. There was no significant advantage of one over the other in respect to revenue.