Author
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Baumhardt, Roland - Louis |
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Howell, Terry |
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Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/4/2005 Publication Date: 1/20/2006 Citation: Baumhardt, R.L., Howell, T.A. 2006. Seeding practices, cultivar maturity, and irrigation effects on simulated grain sorghum yield. Agronomy Journal. 98:462-470. Interpretive Summary: Grain sorghum is well adapted for use in dryland and irrigated cropping systems on the Southern High Plains. Irrigation in this region relies on the declining Ogallala aquifer, and applications are transitioning from full to deficit replacement of evapotranspiration, i.e., crop water use. Our objective was to identify optimum planting date, plant density, row spacing, cultivar maturity, and reduced irrigation combinations to maximize grain sorghum yield using the SORKAM simulation model, long-term (1958-1999) weather records at Bushland, TX, and known Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) properties. Grain sorghum growth and yield was simulated under dryland and limited or full irrigation conditions (rain + irrigation = 0.1 or 0.2 in./d) for all combinations of planting date (15 May, 5 June, 25 June), cultivar maturity (early, medium, late), plant density (48,000 and 64,000 plants/acre), and row spacing (15 and 30 in.). Simulated grain yield increased 7% for narrow compared with wide row spacing independent of other treatments. Under full irrigation, simulated grain yield was unaffected by plant density and increased with earlier planting dates. In contrast, simulated yields for the early-maturing cultivar were greatest under dryland conditions and not different from other tested cultivars for most deficit irrigation conditions. Our results show that early planted late-maturing sorghum maximized yields under full irrigation; however, early-maturity cultivars planted on 5 June were better adapted to both dryland and deficit irrigation for optimum grain yield on a Southern High Plains clay loam soil. Technical Abstract: Grain sorghum [Sorghum bicolor (L.) Moench] is well adapted for use in dryland and irrigated cropping systems on the Southern High Plains. Irrigation in this region relies on the declining Ogallala aquifer, and applications are transitioning from full to deficit replacement of evapotranspiration, ET. Our objective was to identify optimum planting date, plant density, row spacing, cultivar maturity, and reduced irrigation combinations to maximize grain sorghum yield using the SORKAM simulation model, long-term (1958-1999) weather records at Bushland, TX, and known Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) properties. Grain sorghum growth and yield was simulated under dryland and deficit or full irrigation conditions (rain + irrigation = 2.5 or 5.0 mm/d) for all combinations of planting date (15 May, 5 June, 25 June), cultivar maturity (early, medium, late), plant density (12 and 16 plants/m2), and row spacing (0.38 and 0.76 m). Simulated grain yield increased 7% for narrow compared with wide row spacing independent of other treatments. Under full irrigation, simulated grain yield was unaffected by plant density and increased with earlier planting dates. In contrast, simulated yields for the early-maturing cultivar were greatest under dryland conditions and not different from other tested cultivars for most deficit irrigation conditions. Our results show that early planted late-maturing sorghum maximized yields under full irrigation; however, early-maturity cultivars planted on 5 June were better adapted to both dryland and deficit irrigation for optimum grain yield on a Southern High Plains clay loam soil. |
