PLANT WATER RELATIONS, YIELD, AND WATER-USE OF PAPAYA (CARICA-PAPAYA L.) AT DIFFERENT EVAPORATION-REPLENISHMENT RATES UNDER DRIP IRRIGATION

Papaya (Carica papaya L.) water relations, growth, yield, and water us e under drip irrigation at different evaporation-replenishment rates ( 20, 40, 60, 80, 100, and 120% of United States Weather Bureau Class A Pan evaporation) with subsurface drip (at 250 mm depth in the soil) an d surface drip irrigation were investigated at Bangalore, India. Incre asing the evaporation-replenishment rates from 20 to 120% increased th e relative water content (13.2%), transpiration rate (18.8%), plant he ight (21.9%), stem girth (12.5%), fruit number (88.3%), and yield of p apaya (34.6%). Fruit yield differences above 60% evaporation-replenish ment rates were not significant. The water use from 0 to 36 months aft er planting increased with an increase in evaporation-replenishment ra tes. It was 1651 mm and 4208 mm at the 20% and 120% replenishment rate s. Water-use efficiency (WUE) over this period decreased from 58.6 to 30.9 kg ha(-1) mm(-l) at the 20% and 120% replenishment rates, respect ively. Subsurface drip irrigation recorded significantly higher fruit yield (121.4 compared to 110.6 t ha(-1)) and WUE (40.6 compared to 37. 2 kg ha(-1) mm (-1)) than surface drip irrigation.