Sorghum Management Practices Suited to Varying Irrigation Strategies: A Simulation Analysis

• Published in: Agronomy journal 2007-05, Vol.99 (3), p.665-672
• Main Authors: Baumhardt, R.L, Tolk, J.A, Howell, T.A, Rosenthal, W.D
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; crop models; cultivars; deficit irrigation; developmental stages; early development; Fundamental and applied biological sciences. Psychology; grain sorghum; grain yield; irrigated farming; irrigation management; irrigation rates; maturity groups; maturity stage; plant density; planting date; Simulation analysis; simulation models; Sorghum bicolor; SORKAM model; water allocation
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2006.0092

Increasing pumping costs and declining well capacities in regions like the Southern High Plains of Texas are requiring producers to adapt cropping practices for use with irrigation levels that vary between complete replacement of crop evapotranspiration (ET) to none (i.e., dryland production). Grain sorghum [Sorghum bicolor (L.) Moench] is a crop suited to both dryland and various deficit irrigation production systems. Our objectives were to (i) identify cultural practices (planting date, population, and cultivar maturity) that maximize sorghum grain yield for widely varying irrigation strategies; and (ii) consider effective means to allocate available water among irrigation strategies that maximizes the ratio of yield to ET, that is, water use efficiency (WUE). Using the model SORKAM and long-term (1958-1999) weather records from Bushland, TX, we simulated sorghum grain yields on a Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) under dryland (rain) and three deficit irrigation levels (rain + irrigation = 2.5, 3.75, 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, 95 d; medium, 105 d; late, 120 d), and plant density (12 and 16 plants m-2). For 2.5 mm d-1 irrigation level, simulated grain yields were maximized with either early or medium-maturing cultivars planted in early June. In contrast, simulated sorghum yield and WUE increased with a mid-May planting date and later-maturing cultivars for irrigation levels of 3.75 and 5.0 mm d-1. We conclude that spreading water to uniformly irrigate a field with 2.5 mm d-1 produces approximately 16% less grain than concentrating the same water resources to variably irrigate a field at 3.75 or 5.0 mm d-1 with complementary (2:1 and 1:1) dryland areas.