Drip irrigation strategy for tomatoes grown in greenhouse on the basis of fuzzy Borda and K-means analysis method

Abstract

To design a suitable drip irrigation strategies for tomato production, an experiment was laid out in a randomized complete-block design, six treatments, which completely combined with three drip irrigation frequencies and two drip times were carried out in 2020 and 2021 with the variety “Heshengfeilong” tomatoes in the greenhouse. Four single comprehensive evaluation methods: PCA, TOPSIS, MFA, and GRA were used to comprehensively evaluate the fruit quality. Fuzzy Borda combined evaluation was performed on each comprehensive evaluation result that passed the pre-consistency test (Kendall-W). We found that MFA is the most suitable for evaluating the comprehensive fruit quality because its ranking results have the highest correlation coefficient with fuzzy Borda in 2020 and 2021, namely, 0.989 and 0.994, respectively. Total soluble solids (TSS) can be used as a single indicator representing the comprehensive fruit quality because it has a significant positive correlation with the comprehensive quality score in two years. The results of the TOPSIS evaluation of the TSS and the yield show that the optimal treatment in this experiment is for drip irrigation at 9:00, 11:00, 13:00, 15:00, and 17:00. The K-means clustering algorithm was used to determine the change in moisture content corresponding to different temperature ranges and further determine the irrigation strategy, which is the drip irrigation frequency of 5 times/day, and the drip irrigation volume was obtained according to the change in moisture content. During the day (9:00–19:00), the change in the substrate moisture content is divided into three temperature ranges, namely, 5.90–23.98 °C, 23.98–37.42 °C, and 37.42–53.58 °C, corresponding to 0.44%/2 h (40 ml/2 h), 1.34%/2 h (121 ml/2 h), 2.26%/2 h (203 ml/2 h), respectively. During the night (19:00–9:00 the next day), the change in the substrate moisture content is 0.19%/2 h (17 ml/2 h).