Minimum spacing studies for lettuce
Two possibilities exist as ways to eliminate hand thinning in lettuce production: (1) to combine precision planting with the use of a selective thinner; and (2) to plant to a stand, utilizing improved seed environment control with respect to plant protection, soil crust prevention, and moisture control. Regardless of which system the grower chooses, he must decide on a minimum spacing that can be tolerated, without sacrificing head size, quality or yield. If the thinner is used, the cutting mechanism should be set to leave plants as close as possible to that minimum spacing. If planting to a stand is practiced, then the minimum spacing will result in maximum plant population, thereby giving better yield insurance to cover any loss of stand. The purpose of this study was to determine the minimum plant spacing that could be tolerated without yield or quality loss under field conditions.