Effects of different irrigation programs on yield and quality parameters of eggplant (Solanum melongena L.) under greenhouse conditions

This study was carried out to determine the effects of different irrigation programs on yield and quality parameters of eggplant under greenhouse conditions, using Class A pan evaporation calculations and different plant-pan coefficients. Irrigation water was applied through drip irrigation method twice a week during the growing period. Irrigation treatments consisted of five plant-pan coefficients (S1: kcp = nonirrigation, S2: kcp = 0.50, S3: kcp = 0.75, S4: kcp = 1.00 and S5: kcp = 1.25). The amount of irrigation water ranged between 95.2 and 238.7 mm among the treatments. Evapotranspiration (ET) values varied from 93.1 to 466.3 mm for the treatments. The highest yield was obtained from the S3 and S4 treatments. A significant polynomial correlation was obtained between the yield and irrigation water, and between the yield and ET (P < 0.01). This indicated that when irrigation water and ET increased, yield also increased to a certain point. However, when the amount of irrigation water exceeded the plant water requirement, eggplant yield decreased. Yield response factor (Ky) was determined as 0.81. Since Ky < 1, eggplants were not sensitive to water deficiency. In addition, the highest water use efficiency (WUE) and irrigation water use efficiency (IWUE) values were calculated in the S3 (12.9 kgm-3) and S2 (44.2 kgm-3) treatments, while the lowest WUE and IWUE values were calculated in the S5 (7.9 and 15.5 kgm-3) treatment to which the highest irrigation water was applied. This finding indicated that WUE and IWUE values decreased with the increasing irrigation water and ET. These results suggested that S3 (kcp = 0.75) treatment can be the most appropriate irrigation program for eggplant with higher yield and WUE under greenhouse conditions.Key words: Eggplant, yield response factor, water use efficiency, Class A pan, evapotranspiration