Planting Date, Water Management, and Maturity Length Relations for Irrigated Grain Sorghum

Grain sorghum [Sorghum bicolor (L) Moench] is produced under widely varying planting dates and irrigation management in the Southern High Plains. This study was conducted to determine optimum planting date and maturity length hybrid under varying irrigation levels. The effects of medium and medium-late maturity sorghum hybrids on yield, water use, and water use efficiency (WUE) were investigated for three irrigation regimes; no post-plant irrigation, limited irrigation (one or two growing season applications), and adequate irrigation (three or four growing season applications). Planting dates were from early May through late June of 1989, 1990, and 1991 at Bushland, Texas. Grain yields averaged highest (about 8.9 Mg/ha) for both hybrids under adequate irrigation when planted near 23 May. When planting very early (near 5 May) with adequate irrigation, the medium-late hybrid was slightly more productive than the medium hybrid; but when planting in June, the medium hybrid was slightly more productive. With limited irrigation, the medium hybrid was slightly more productive (yield of 7.2 Mg/ha and WUE of 1.3 kg/m3) than the medium-late hybrid (yield of 6.9 Mg/ha and WUE of 1.2 kg/m3). Under a major soil-water deficit without any post-plant irrigations, the medium hybrid was more productive. With planting dates in May and adequate irrigation, either maturity-length hybrid would give acceptable performance. When planting in June, a medium hybrid would be acceptable for both limited and adequate irrigation management.