Effects of deficit irrigation on growth, yield, and fruit quality of eggplant under semi-arid conditions
Eggplant (Solanum melongena L.) cv. Pala was grown in the field from March to August 2001 in order to investigate the effects of deficit irrigation on fruit yield and quality (i.e. soluble dry matter, fruit size), leaf relative water content, leaf area index (LAI), leaf chlorophyll concentration, electrolyte leakage, and leaf nutrient composition (N, P, K) in eggplant. Treatments were: (1) well-watered treatment receiving 100% replenishment of A pan evaporation on a daily basis (C); (2) water-stressed treatment receiving 90% replenishment of A pan evaporation at 4-day intervals (WS); (3) water-stressed treatment receiving 80% replenishment of A pan evaporation at 8-day intervals (WS); and (4) water-stressed treatment receiving 70% replenishment of A pan evaporation at 12-day intervals (WS). A total of 1276 mm of water was applied to C treatment, and the seasonal water use of eggplant ranged from 905 to 1373 mm. The C treatment had the highest yield as well as the largest and the heaviest fruit. WS did not significantly affect fruit yield or fruit size but fruits were slightly lighter; plant height, stem diameter, and shoot and root dry weights, LAI, leaf relative water content, nutrient concentrations, and chlorophyll concentrations in leaves were the same as in C; SDM was higher than C. The WS and WS treatments caused reductions in most parameters, except water-soluble dry matter (SDM) concentrations in fruits, compared with the unstressed (C) treatment. WS and WS treatments enhanced fruit quality (in terms of SDM) and increased electrolyte leakage compared with C. WS and WS reduced marketable yield by 12% and 28.6%, respectively, compared with C. The highest total water use efficiency and irrigation water use efficiency were in WS, resulting in a 20.4% water saving compared with C. The results revealed that the optimal irrigation strategy for eggplant could depend on balancing the situational requirements in terms of irrigation water, yields, and fruit size and quality.