Water use efficiency and irrigation response of cotton cultivars under sub-surface drip irrigation in West Texas
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The High Plains Aquifer is the source of nearly all agriculture irrigation water in the Texas High Plains, and its resources are being depleted due to withdrawals that greatly exceed recharge. Decreasing water availability has led to research on water use requirements of most agronomic crops, including yield and quality impacts of deficit irrigation. Some drought-tolerant crops such as cotton (Gossypium hirsutum L.), can adapt well to deficit irrigation. The objectives of this study were to i) evaluate the water use efficiency and boll distribution patterns of cotton cultivars at varying levels of sub-surface drip irrigation from severe-deficit to fully irrigated, ii) compare growth and yield characteristics between cultivars at varying irrigation levels, and iii) determine yield stability under deficit irrigation in West Texas. Yield, water use efficiency and boll distribution were compared during 2010 and 2011 for cultivars DP 0912, DP 0924, DP 0935, DP 1028, DP 1032, DP 1044, and FM 9160. In 2010, FM 9160, DP 1044, and DP 0912 had the three highest average yields and water use efficiencies. DP1044 and FM9160 performed very well under deficit irrigation. In 2011 cultivar DP1044 again was a top performer along with DP0935 and DP0924. Average yield ranges of 1077 to 1256 kg ha-1for 2010 and 958 to 1074 kg ha-1 for 2011 were common to those produced in West Texas. Water use efficiency was also common for West Texas with ranges of 0.23 to 0.27 for 2010 and 0.17 to 0.19 kg m-3 for 2011. Boll distribution patterns varied significantly between cultivars and within irrigation treatments. Three cultivars (DP1044, FM 9160 and DP 0935) increased fruit production near the top of the plants in response to irrigation, and also had good yield and yield stability; their yield patterns may be favorable for limited water conditions in the Texas High Plains.