Cotton growth and development under different tillage systems

Adoption of reduced tillage systems is a means to lower production costs and improve soil productivity, but yield of cotton (Gossypium hirsutum L.) can be variable. Our objective was to determine when and how different tillage systems affected growth quantities and yield. The effect of conventional tillage (CT), ridge tillage (RT), and no tillage (NT) on crop growth rate (CGR), leaf area index (LAI), net assimilation rate (NAR), fruiting form numbers and weights, plant population, and crop yield was determined on a Gigger silt loam (fine-silty, mixed, thermic, Typic Fragiudalf). In 1991, the NT system produced a maximum prebloom CGR of It g m(-2) d(-1) compared with 7 and 7.5 g m(-2) d(-1) for the CT and RT systems, respectively. In 1992, a year with more adverse growing conditions, prebloom CGR values were lower for all systems but NIT was greatest at 7 g m(-2) d(-1). Differences in prebloom CGR among tillage systems in 1994 were similar to the1992 results although values were similar to those of 1991. Prior to blooming, the RT system produced a consistently lower CGR than one or both of the other systems. Differences in LAI corresponded to CGR differences, but there were no differences among the three tillage systems in NAR. Greater early CGR led to faster ontogenic development and eventually to greater lint yields. Lint yields averaged 1057 kg ha(-1) for NT, 1007 kg ha(-1) for CT, and 890 kg ha(-1) for RT. The NIT system, which in this study had the greatest prebloom CGR and lint yield, was the conservation tillage system with the greatest production potential in this soil type. Early-season differences in soil characteristics among tillage systems at 0 to 0.15 m was considered a factor.