Irrigation depths, soil cover and phosphate fertilization on gas exchanges of okra

The okra crop stands out as a viable alternative for family farmers in regions of semi-arid climate, due to its acceptance in the market and for being rich in vitamins, fibers and minerals. Thus, this study aimed to evaluate the gas exchanges of okra under water depths, soil cover and phosphate fertilization, in an experiment carried out in the municipality of Catolé do Rocha-Paraíba, Brazil, in the period from November 2014 to April 2015. The experimental design was randomized blocks with a 2 x 2 x 2 factorial scheme, referring to two irrigation depths (100 and 50% of crop evapotranspiration – ETc), with and without soil cover, with and without phosphate fertilization, with four replicates. Gas exchanges were determined in the flowering stage through the CO2 assimilation rate, stomatal conductance, transpiration, internal CO2 concentration, water use efficiency and instantaneous carboxylation efficiency. There is positive influence of phosphate fertilization and soil cover on the gas exchanges of okra plants under different conditions of water availability in the soil. Phosphate fertilization and soil cover mitigate the effects of water stress on okra plants and, when associated, increase the photosynthetic efficiency and water use efficiency of the plants.