Optimization of irrigation-drainage scheme for tomato crop based on multi-index analysis and projection pursuit model

Abstract

Various indexes should be considered when developing a suitable irrigation and drainage scheme for crops. Our study chosen tomato as plant material and conducted a field experiment under saline soils. Nine treatments distinguished by different irrigation quotas and different drain ditch depths were used for the optimization of irrigation-drainage scheme. A flooding irrigation treatment with no surface drainage was adopted as control. The system of evaluation indexes was established in comprehensive consideration of the electrical conductivity and nutrient of soil, and the water use efficiency, nitrogen use efficiency, quality and marketable yield of tomato. Moreover, the multi-index analysis and projection pursuit (PP) model were used to evaluate the irrigation-drainage schemes according to the observed values of these six evaluation indexes. Results showed that different irrigation-drainage treatments decreased the electrical conductivity in plough layer by 24.6–51.3%, and increased the tomato water use efficiency and nitrogen use efficiency by 0.3–24.2% and 20.3–96.0%, respectively. The tomato marketable yield was increased by 14.4–31.3% with the irrigation-drainage treatments when compared to the control. As analyzed by the PP model, I3D1 (300 m3 hm-2 of irrigation quota combined with 10 cm of ditch depth) was the treatment that possessed best comprehensive benefits due to the highest projection value of 1.6724 thus was recommended by this study as the optimal irrigation-drainage scheme.