Evaluation of F-2 genotypes of cotton for conservation tillage

Reduced plant populations often occur when cotton (Gossypium hirsutum L.) is grown in conservation tillage systems. Our objectives were to determine the potential of exploiting hybrid vigor in F-2 cotton to improve stand establishment and yield in conservation tillage systems and to compare the expression of heterosis in this system with that in a conventional tillage system. This held study was conducted in 1991, 1992, and 1994 on a Norfolk loamy sand soil (fine-loamy, silicious, thermic, Typic Kandiudult) near Florence, SC. Five cotton cultivars were crossed in a half-diallel design to generate 10 F-2 generation genotypes. The parent and F-2 generations were planted into conservation tillage plots that had desiccated crimson clover (Trifolium incarnatum L.) as a surface mulch and into conventional tillage plots, Cotton stands were similar for both generations in both tillage systems in 1991. At 2 wk after planting in 1992, a tillage x (Parent vs, F-2) interaction (P less than or equal to 0.05) occurred for plant population as stands in conventional tillage were 7.5 and 8.4 plants m(-1) for the parent and F-2 generations, respectively, while stands in conservation tillage were 4.1 plants m(-1) for the parents and 4.2 plants m(-1) for the F-2 generation. At 2 wk after planting in 1994, stands of the F-2 generation were 1.3 plants m(-1) greater than the parents averaged over both tillage systems, Yield differences occurred only in 1992, when the F-2 generation had greater lint yield than the parents in both tillage systems. The results suggest that growing F-2 genotypes may improve cotton stand establishment and yield under certain conditions in conservation tillage systems, but the amount of improvement will be similar to that found in conventional tillage.