Evapotranspiration and yield of okra as affected by partial root-zone furrow irrigation

Partial root-zone drying or partial root-zone irrigation is a newly proposed water saving technique which may improve water use efficiency and nutrient uptake by a crop without affecting its yield. A study was conducted to investigate the response of furrow-irrigated okra to partial root zone drying in relation to cropevapotranspiration (ETc), vegetative growth, yield, and nutrient use efficiency in a sandy loam soil. The experiment was conducted during December-March with three furrow irrigation strategies: alternate partial root-zone irrigation (APRI), fixed partial root-zone irrigation (FPRI), and full root-zone irrigation (FRI). Two levels of irrigation: 25% available soil moisture depletion (ASMD) and 50% ASMD were imposed under each furrow treatment. The plant vegetative growth was significantly (P<0.05) higher in FRI, whereas the pod yield was more in APRI. Lower depletion soil water treatment produced higher vegetative growth and yield. However, APRI at 50% ASMD resulted in highest irrigation water use efficiency (IWUE) for pod yield, and FPRI at 25% ASMD resulted in highest IWUE for total biomass. The maximum ETc was observed under FRI, followed by APRI. The crop co-efficient (Kc) values of 0.38, 0.74, 0.98 and 0.49 may be used in initial growth stage, mid growth stage, final growth stage, and maturity stage of okra, respectively, to estimate the volume of irrigation water under APRI. Partial factor roductivity for the nutrients (N, P and K) followed the similar trend as pod yield. Root biomass of the crop was more in FPRI, where as total root length was more in APRI. The higher root length with finer roots, in conjunction with better nutrients availability in soil produced the higher nutrients content in leaves and pods of alternate partially irrigated plants. Overall, these results reveal that the application of optimum quantity of water through APRI at 50% ASMD could impose desirable water stress on okra plants, improving their fruit yield and quality, without producing higher vegetative growth.