SORGHUM MANAGEMENT PRACTICES SUITED TO VARYING IRRIGATION STRATEGIES: A SIMULATION ANALYSIS

Authors: Baumhardt, Roland; Tolk, Judy; Howell, Terry; ROSENTHAL, W - TAES

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2007
Publication Date: 5/1/2007
Citation: Baumhardt, R.L., Tolk, J.A., Howell, T.A., Rosenthal, W.D. 2007. Sorghum management practices suited to varying irrigation strategies: A simulation analysis. Agronomy Journal. 99:665-672.

Interpretive Summary: Volatile fuel costs for irrigation and declining well capacity on the southern High Plains have led producers to seek cropping practices for use with dryland production and irrigation varying from complete to deficit replacement of crop evapotranspiration (ET). Grain sorghum [Sorghum bicolor (L.) Moench] is a crop suited for both dryland and variable irrigation. Our objective was to compare simulated sorghum grain yield and water use efficiency (WUE) for several planting dates, populations, and cultivar maturity combinations under variable supplemental irrigation strategies to identify cultural practices for use with the broadest production scenarios. Using the model SORKAM and long-term (1958-1998) weather records from Bushland, TX, we simulated sorghum grain yields on a Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) under dryland (rain only) and 3 deficit irrigation levels (rain + irrigation = 0.1, 0.15, or 0.2 in./d) for all combinations of planting date (mid-May, 15 May; early June, 5 June; and late June, 25 June), cultivar maturity (early, medium, late), and plant density (12 and 16 plants m-2). For 0.1 in./d irrigation level, optimum simulated grain yields were achieved with either early or medium maturing cultivars planted in early June (5 June). In contrast, simulated sorghum yield and WUE increased with a mid-May planting date and later maturing cultivars with irrigation levels of 0.15 and 0.2 in./d. Our results show that, concentrating limited water resources on a small area to meet a 0.15 in./d ET for grain sorghum increases yield compared with spreading the same amount of water for a 0.1 in./d ET on a larger area.

Technical Abstract: Volatile fuel costs for irrigation and declining well capacity on the southern High Plains have led producers to seek cropping practices for use with dryland production and irrigation varying from complete to deficit replacement of crop evapotranspiration (ET). Grain sorghum [Sorghum bicolor (L.) Moench] is a crop suited for both dryland and variable irrigation. Our objective was to compare simulated sorghum grain yield and water use efficiency (WUE) for several planting dates, populations, and cultivar maturity combinations under variable supplemental irrigation strategies to identify cultural practices for use with the broadest production scenarios. Using the model SORKAM and long-term (1958-1998) weather records from Bushland, TX, we simulated sorghum grain yields on a Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) under dryland (rain only) and 3 deficit irrigation levels (rain + irrigation = 2.5, 3.8, or 5.0 mm d-1) for all combinations of planting date (mid-May, 15 May; early June, 5 June; and late June, 25 June), cultivar maturity (early, medium, late), and plant density (12 and 16 plants m-2). For 2.5 mm d-1 irrigation level, optimum simulated grain yields were achieved with either early or medium maturing cultivars planted in early June (5 June). In contrast, simulated sorghum yield and WUE increased with a mid-May planting date and later maturing cultivars with irrigation levels of 3.75 and 5.0 mm d-1. Our results show that, concentrating limited water resources on a small area to meet a 3.75 mm d-1 ET for grain sorghum increases yield compared with spreading the same amount of water for a 2.5 mm d-1 ET on a larger area.