| cope and method of study. Field experiments were conducted in 1996 and 1997 to evaluate the effects of six johnsongrass densities on picker- and stripper-harvest efficiency, fiber properties, loan rate (value), and lint yield of cotton. Field experiments were also conducted in 1997, 1998, and 1999 to evaluate weed-control systems in grain sorghum production. Variables evaluated were net returns, total returns, variable cost, grain sorghum yield, weed control, and crop injury. Weed control had an upper limit cost of ;Findings and conclusions. Machine harvest efficiencies were lower for the picker- versus the stripper-harvest in both years; however, harvest method did not affect fiber properties. Micronaire differences were detected at a density of 15 weeds/15 m of row in 1996 and 8 weeds/15 m of row in 1997, when compared to the weed-free check. Length differences were detected at a density of 3 weeds/15 m of row in 1996, and this difference was higher than the weed-free check. In 1997, no differences were detected. Strength differences were not detected in 1996, when compared to the weed-free check. In 1997, a difference was detected at densities of 3, 8, and 15 weeds/15 m of row (284 mN/tex) when compared to the weed-free check (304 mN/tex). Uniformity showed no differences in either year. In all cases the stripper-harvested cotton loan rate in 1997, was lower than the stripper-harvested values in 1996, and picker-harvested values in both years. Lint yield was reduced in 1996 by 29.2 kg/ha or 3.5% for stripper-harvested cotton and 32 kg/ha or 3.9% for picker-harvested cotton for each increase by one johnsongrass plant/15m of row. In 1997, stripper- and picker-harvested cotton was reduced by 43 kg/ha or 5.2 and 5.5% for each increase by one johnsongrass plant/ 15m of row, respectively.;Metolachlor applied PRE followed by 2,4-D POST was the only treatment that consistently provided excellent weed control for Palmer amaranth and large crabgrass in all experiments. Profitable net returns were achieved when weed-control costs exceeded the target cost of... |
