Hay Yield and Water Use Efficiency of Alfalfa under Different Irrigation and Fungicide Regimes in a Semiarid Climate

Alfalfa is one of the most nutritive and high-yielding forage legumes planted in rotation with cereal crops across the United States. Under semiarid and arid climates with limited water resources, sustainable management of the available resources is required. The objective of this study was to investigate the effect of different irrigation regimes and fungicide applications on alfalfa in the high desert region of the Colorado Plateau of the U.S. Field experiments were conducted during the 2012–2014 period. Alfalfa was planted in fall 2012, uniformly irrigated for crop establishment and subjected to seven different irrigation regimes after the first cut in spring 2013. Alfalfa was treated by fungicide application and was harvested at 10% blooming. The maximum amounts of applied water were 350, 300, 208, and 312 mm, respectively, during the first, second, third, and fourth regrowth cycles in 2013, and 373, 282, 198, and 246 mm in 2014 for the respective regrowth cycles in 2014; the seasonal applied irrigation amount varied from 711 to 1171 mm in 2013 and from 328 to 1100 mm in 2014. The results showed non-significant effect of fungicide application on the forage yield. Alfalfa forage yield was significantly affected by the irrigation regimes and showed a third order polynomial relationship with the applied irrigation amounts during each regrowth cycle and on seasonal scale. Forage yield decreased from the first cut to the fourth cut and the annual forage varied from 10.6 to 25.7 Mg/ha for the treated alfalfa and from 11.5 to 25.6 Mg/ha for the non-treated alfalfa. Forage yield at each cut accounted for 39.6, 24.2, 17.6, and 18.6% of the 2013 season forage yield and 31.4, 23.8, 21.6, and 23.2% of the 2014 season forage yield, for the first, second, third, and fourth cut, respectively. Alfalfa water use efficiency varied from 0.06 to 3.3 kg/m3. The relationships developed in this study could be used by forage growers, crop consultants, and project managers for decision making and planning to improve the productivity of water under the semiarid and arid climate of New Mexico and the surrounding regions.