DETERMINING WATER-YIELD RELATIONSHIP, WATER USE EFFICIENCY, SEASONAL CROP AND PAN COEFFICIENTS FOR ALFALFA IN A SEMIARID REGION WITH HIGH ALTITUDE

A field study was conducted to determine effects of seasonal deficit irrigation on plant dry forage yield and water use efficiency of alfalfa for a 2-year period in the semiarid region with high altitude. In addition, the seasonal crop and pan coefficients k(c) and k(p) of alfalfa was determined in full irrigation conditions. Irrigations were applied when approximately 50% of the usable soil moisture was consumed in the effective rooting depth at the full irrigation treatment. In deficit irrigation treatments, irrigations were applied at the rates of 80, 60, 40, 20 and 0% of full irrigation treatment on the same day. Irrigation water was applied by hose-drawn traveler with a line of sprinklers. Seasonal actual evapotranspiration, total dry forage yield and water use efficiency was the highest in full irrigation conditions and the lowest in continuous stress conditions. The linear relationship between seasonal actual evapotranspiration and total dry forage yield was obtained. According to the averaged values of 2 years, yield response factor (k(y)) was 1.33. Both seasonal k(p) and k(c) were determined as 0.86 for alfalfa, when combined values of 2 years.