Partial root-zone drying irrigation for higher water use efficiency in papaya (Carica papaya L.)

Abstract: A field experiment to standardize the partial root-zone drying irrigation in papaya (Carica papaya L.) cultivar ‘Red Lady’ indicated that replenishing 70 % of the evaporative demand and changing the irrigation sides once in 12 days stored higher soil moisture (14.6 %) in the root zone. Irrigation meeting 60 % ER found to enhance the photosynthetic rate (13.9µ mol/m²/s) significantly, while shifting the irrigation at 16 days was found to reduce the rate (9.9 µ mol/m²/s). ABA production increased with an increase in the interval between the changing irrigation sides. Vertical growth of roots was significantly higher (67.3 cm) when irrigation was scheduled meeting 60 % pan evaporation with irrigation side changing once in 16 days. Replenishing 60 % of evaporation recorded significantly higher number of fruits (46.1/plant) and further changing the irrigation sides once in 12 days found to yield considerably more papaya fruits (53 /plant) and total yield (32.4 kg/plant) accounting to 100 t/ha. This treatment also recorded substantially higher water use efficiency (100.4 kg/ha.mm), saving 14.3 % water. Further, scheduling irrigation at 60 % ER and changing the irrigation sides at 12 day intervals was found to be more economical with higher gross returns (Rs. 10,00,000), net returns (Rs. 6,09,340) and benefit-cost ratio (2.60).