Long-Term Winter Wheat (\u3ci\u3eTriticum aestivum\u3c/i\u3e L.) Seasonal Irrigation Amount, Evapotranspiration, Yield, and Water Productivity under Semiarid Climate

A long-term field experiment was conducted from 2002 to 2014 for the evaluation of yield and water productivity of three winter wheat varieties—Kharkof, Scout 66, and TAM107—under sprinkler irrigation at New Mexico State University Agricultural Science Center at Farmington, NM. Winter wheat daily evapotranspiration was estimated following the United Nations Food and Agriculture Organization FAO crop coefficient approach (ETc = Kc ETo), and crop water use efficiency (CWUE), evapotranspiration water use efficiency (ETWUE), and irrigation water use efficiency (IWUE) were estimated for each growing season. There was inter-annual variation in seasonal precipitation and irrigation amounts. Seasonal irrigation amounts varied from 511 to 787 mm and the total water supply varied from 590 to 894 mm with precipitation representing a range of 7.7–24.2%. Winter wheat daily actual evapotranspiration (ETc) varied from 0.1 to 14.5 mm/day, averaging 2.7 mm/day during the winter wheat growing seasons, and the seasonal evapotranspiration varied from 625 to 890 mm. Grain yield was dependent on winter wheat variety, decreased with years, and varied from 1843.1 to 7085.7 kg/ha. TAM107 obtained the highest grain yield. Winter wheat CWUE, IWUE, and ETWUE were also varietal dependent and varied from 0.22 to 1.01 kg/m3, from 0.26 to 1.17 kg/m3, and from 0.29 to 0.92 kg/m3, respectively. CWUE linearly decreased with seasonal water, and IWUE linearly decreased with seasonal irrigation amount, while CWUE, IWUE, and ETWUE were positively correlated with the grain yield for the three winter wheat varieties, with R2 ≥ 0.85 for CWUE, R2 ≥ 0.69 for IWUE, and R2 ≥ 0.89 for ETWUE. The results of this study can serve as guidelines for winter wheat production in the semiarid Four Corners regions. Additional research need to be conducted for optimizing winter wheat irrigation management relative to planting date and fertilization management to reduce the yield gap between winter wheat actual yield and the national average yield