DOUBLE AND MONOCROPPED WHEAT AND GRAIN SORGHUM UNDER DIFFERENT TILLAGE AND ROW SPACINGS

Abstract

Water is often the most limiting factor in producing the crop following wheat in regions with adequate frost-free days to permit double-cropping. To more fully utilize climatic resources, land, and machinery after the harvest of wheat grain, we conducted a field study on a Wynona silt loam soil (Cumulic Haplaquolls) to analyze the effects of tillage and row spacings on soil water content and yields of monocropped (MC) and double-cropped (DC) wheat and grain sorghum under rain fed conditions. When planted at the same time and over a 4-year period, double-cropped wheat (DCW) yielded 2260, compared with 2890 kilograms per hectare for monocropped wheat (MCW). Due to drought, grain sorghum as the second crop failed to produce grain 1 (1978) out of 4 years. For the 3 years of successfully double-cropping grain sorghum (DC-GS), conventional tillage, double-cropped grain sorghum (CT-DCGS) in 50-centimeter rows yielded 4080, compared with 3810 kg/ha in 75-cm rows. No-tillage, double-cropped grain sorghum (NT-DCGS) in 50-cm rows yielded 3830 compared with 3590 kg/ha in 75-cm rows. When planted at the same time as the DC-GS, conventional tillage, monocropped grain sorghum (CT-MCGS) in 50-cm rows yielded 4150 compared to 3760 kg/ha in 75-cm rows. For the double-cropped treatments, water content in 120 cm of soil profile was not significantly affected during the grain sorghum growing period by tillage and row spacings; however, tillage and planting operations must be timely to prevent loss of water in the soil-seed environment when attempting to establish a stand for the double crop. For the 3 years of successful double-cropping, an average of only 12 percent of the precipitation that fell from mid-June (after wheat grain harvest) to early October was detected as stored water in the monocropped wheat plots. More grain production and more effective use of annual precipitation and soil water were achieved 3 out of 4 years when wheat and grain sorghum were double-cropped.