Effects of irrigation upper and lower limits on growth and yield of eggplant under partial rootzone conditions

The object of this study was to explore the effect of different irrigation upper and lower limits on crop growth, gas exchange and yield, the glass-soil boxes experiment was conducted about two irrigation methods (conventional drip irrigation (CDI), alternate partial root zone drip irrigation (APRDI)). The influence of three levels of irrigation upper and lower limits (CDI, as control, in which soil water content (SWC) in the whole root system ranged from 85%-100% of field capacity (FC); APRDI85-50, in which on one side of the divided root SWC was between 85%-100% of FC and on the other side it was maintained the range of 50%-85% of FC; PRD70-30, in which on one side of the divided root SWC was between 70% to 100% of FC and on the other side it was allowed to vary from 30% to 70%) on growth, gas exchange, yield, and water use ef?ciency in eggplant was studied. Results showed an obvious decrease of leaf water potential up to 19% and 26.4% in APRDI plants compared with CDI. Stomata conductance and transpiration rate in plants with APRDI were significant lower compared to control. However, photosynthetic rate increased by 14.7% in APRDI85-50 plants and photosynthetic rate of APRDI70-30 plants was similar to CDI treatment, thus increased instantaneous transpiration efficiency by 26.1% in APRDI85-50 treatment and 5.1% in APRDI70-30 treatments, respectively, compared to CDI. APRDI treatments triggered root growth, significantly increased root dry weight and root density, and effectively controlled vegetative growth. Compared to CDI treatment, an increase of 43.4% in irrigation water use efficiency was reached in APRDI85-50, yield also increased by 10.8% in APRDI85-50 treatment. However, the irrigation water increased by 29.4% in CDI treatment compared to APRDI85-50 treatment. These results showed that the APRDI85-50 treatment was a feasible irrigation pattern.