Growth, yield, and water use of okra (Abelmoschus esculentus) and eggplant (Solanum melongena) as influenced by rooting volume

Many experiments are conducted in simulated confined spaces to provide controlled environments where plants are grown in pots with limited rooting volume to characterise fundamental physiological responses of plants to stress conditions such as soil water, soil salinity, irrigation water salinity, and plant nutrition. However, rooting volume in the pots can have a limiting effect on overall plant growth to varying degrees. This study was undertaken to quantify the effects of widely differing rooting volume on growth, yield, and water use of eggplant (Solanum melongena) and okra (Abelmoschus esculentuts). Eggplant and okra experiments were conducted similarly, but as separate experiments. Both plants were grown in 3.6-litre (P1), 16-litre (P2), 36-litre (P3), and 52-litre (P4) pots. For eggplant and okra, evapotranspiration (ET) and all of the growth parameters including plant height, stem diameter, root and vegetative dry weight, root length, number of branches and fruit, and fruit yield significantly increased with increasing rooting volume. Pot volume started to affect plant height and ET after 3 weeks from transplanting. For both experiments, the highest yield and the highest yield based water-use efficiency (WUE(yield)) were obtained from the P4 and P3 treatments, respectively. The highest WUE based on total biomass (WUE(biomass)) was obtained from the P4 and P3 treatment of eggplant and okra, respectively. Both experiments exhibited similar morphological changes such as decreases in plant height, stem diameter, branching, root and vegetative dry weight, and root length to root restriction. As a result of this study it can be concluded that a pot size of 36 litres (P3) may be enough for okra growth, but even a 52-litre (P4) pot size may not provide unrestricted rooting volume for eggplant growth.