Comprehensive evaluation of regulated deficit irrigation schedule of greenhouse eggplant based on different weight methods combined with TOPSIS model

To optimize regulated deficit irrigation strategy of facility crops and achieve goal of water saving, high production and quality, taking eggplant grown in greenhouse as the object, and according to average field water capacity（θ_f）in depth of 0 to 60 cm soil layer, two water deficit levels were set at seedling stage, flowering and picking stages, respectively（severe water deficit was 50%～55% θ_f ; mild water deficit was 70%～75%θ_f）, with 80%～85%θ_f as a control（CK）．Effects of regulated deficit irrigation on plant growth（plant height, leaf area index LAI）, yield composition（aboveground dry matter mass AB, single fruit mass WS, transverse diameter TD, longitudinal diameter LD, yield）, fruit quality（soluble sugar SSC, soluble protein SPC）, and water use（water consumption ET, water use efficiency WUE, irrigation water use efficiency）were studied．TOPSIS model combined with information and CRITIC weight methods were introduced to evaluate each strategy．Results showed that plant height and LAI of greenhouse eggplant could be promoted when seedling were exerted mild water regulation deficit, while fruit AB, WS, TD and LD were significantly influenced when flowering exerted mild water regulation deficit．There was no effect on yield formation when seedling or picking stage exerted mild water regulation deficit．The highest yield, WUE and IWUE were obtained by applying mild water regulation deficit at flowering stage, and ET was reduced by 11.6% compared with CK treatment．Applying severe water deficit at seedling stage or flowering stage was conducive to increasing SSC, while increasing SPC was not conducive to applying severe water deficit strategy．Regulated deficit irrigation strategy was evaluated by using TOPSIS multi-objective comprehensive analysis method, and found that seedling and flowering keep 80%～85%θ_f, while picking stage exerted 70%～75%θ_f could achieve optimization of fruit morphology, quality and water use efficiency．In short, applying mild water deficit at picking stage and maintaining CK level in other two stages was the best regulated deficit irrigation strategy for greenhouse eggplant cultivation．