EARLY AND LATE MATURING GRAIN SORGHUM UNDER VARIABLE CLIMATIC CONDITIONS IN THE TEXAS HIGH PLAINS.

In the Texas High Plains, variable climatic conditions prevail between and within growing seasons. As this area continues to experience drought conditions and water resources for irrigation become more limited, sorghum [Sorghum bicolor (L.) Moench] production may become a more popular choice to sustain profitable crop water productivity with limited water. Regional sorghum production functions are helpful in strategizing adaptation methods for coping with climatic variability, but new varieties often exhibit new production functions. This article compares sorghum responses of grain yield, evapotranspiration (ET), water use efficiency (WUE), and irrigation water use efficiency (IWUE) of a late maturing (LM) and early maturing (EM) hybrid during three recent growing years exhibiting climatic variability (2009-2011). The hybrids were irrigated at levels of 80%, 55%, 30%, and 0% replenishment of soil water depletion to field capacity (FC). Mean maximum daily air temperatures and mean daily reference evapotranspiration (grass) for the 2009 (28.2°C, 6.5 mm d^-1) and 2010 (28.6°C, 6.4 mm d^-1) growing seasons were similar; in 2011, these parameters were considerable greater (32.6°C and 8.8 mm d^-1, respectively). For both hybrids, dry grain yields were greatest in 2009 in the I80% treatment at 9.80 and 8.04 Mg ha^-1 for the LM and EM hybrids, respectively. For irrigation treatment amounts of 80% replenishment of soil water to FC, grain yields in the LM hybrid were always greater compared with the EM hybrid. However, WUE in the EM hybrid in 2009 and 2011 was 27% and 29% greater, respectively, than in the LM hybrid. Grain yield responses in both hybrids were most sensitive to the exceptional drought year of 2011 where irrigation applied at less than 80% replenishment of soil water to FC greatly reduced grain yields. Irrigation applied at less than 55% replenishment produced minimal to no grain yields. [ABSTRACT FROM AUTHOR]