Evaluation of Suitable Water–Zeolite Coupling Regulation Strategy of Tomatoes with Alternate Drip Irrigation under Mulch

Abstract

The water (W; W50, W75, and W100)–zeolite (Z; Z0, Z3, Z6 and Z9) coupling (W-Z) regulation strategy of high-quality and high-yield tomato was explored with alternate drip irrigation under mulch. Greenhouse planting experiments were used in monitoring and analyzing tomato growth, physiology, yield, quality, and water use efficiency (WUE). Suitable amounts of W and Z for tomato growth were determined through the principal component analysis (PCA) method. Results showed that tomato plant height (Ph), stem thickness (St), root indexes, leaf area index (LAI), photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), organic acid (OA), and yield showed a positive response to W, whereas nitrate (NC), vitamin C (VC), soluble solid (SS), intercellular CO2 concentration (Ci), fruit firmness (Ff), and WUE showed the opposite trend. The responses of Ci and Ff to Z were first negative and then positive, whereas the responses of other indexes to Z showed an opposite trend (except yield under W50). The effects of W, Z, and W-Z on tomato growth, physiological, and quality indexes and yield were as follows: W > Z > W-Z; the effects on WUE were as follows: Z > W > W-Z. The two principal components of growth factor and water usage factor were extracted, and the cumulative variance contribution rate reached 93.831%. Under different treatments for tomato growth, the comprehensive evaluation score F was between −1.529 and 1.295, the highest treated with Z6W100, the lowest treated with Z0W50. The PCA method showed that under the condition of alternate drip irrigation under mulch, the most suitable W for tomato planting was 100% E (E is the water surface evaporation), and the amount of Z was 6 t·ha−1.