Consumptive water-use efficiency of alfalfa (Medicago sativa L.) grown under three irrigation regimes.

Abstract

Consumptive water-use efficiency of four alfalfa (Medicago sativa L.) cultivars was determined under field conditions at the Soil Conservation Service Plant Materials Center, Tucson, Arizona. The cultivars were ‘Mesa-Sirsa,’ ‘Sonora,’ ‘EI-Unico,’ and ‘Moapa.’ The cultivars were grown under three irrigation regimes. Plants were irrigated when approximately 30, 60, and 90% of the available soil moisture was depleted from the upper 91.4 cm of root zone. These irrigation regimes were designated as high, medium, and low, respectively. Consumptive water-use efficiency, yield, percentage protein, leaf to stem ratio, percentage dry matter, and stand decline were determined on each cultivar grown under the three soil-moisture regimes. Cultivars differed significantly in the units (kg) of water required to produce a unit (kg) of dry matter during 1968 but not in 1969. Average consumptive water-use efficiency values were 519, 524, 535, and 547 for El-Unico, Mesa-Sirsa, Sonora, and Moapa, respectively, in 1968. All cultivars were more efficient in water-use under the low soil-moisture regime. Average water efficiency values were 403, 493, and 698 for the low, medium, and high soil-moisture regimes, respectively, in 1968. Average water efficiency values for the low, medium, and high regimes in 1969 were 541, 598, and 894, respectively. Cultivars differed significantly in forage production in 1968 but not in 1969. El-Unico produced the most forage during both growing seasons. In 1968 plants grown under the high soil-moisture regime produced significantly less forage than plants under the low and medium regimes. Percentage protein, leaf to stem ratio, and stand decline were not affected by soil 'moisture. Alfalfa cultivars with the highest forage production were the most efficient in water-use under field conditions.