Interactive effect of irrigation and polymer-coated potassium chloride on tomato production in a greenhouse

As a main crop cultivated in greenhouses, tomato (Solanum lycopersicum L.) has become one of the most popular vegetables in the world. Tomato is water and nutrient demanding. Although effects of irrigation and nitrogen nutrition management on tomato growth have been widely investigated, few studies have been conducted on the interactive effects of irrigation and potassium (K) fertilizers, especially those of irrigation and polymer-coated potassium chloride (PCPC). In this study, a pot experiment was conducted with three PCPC application rates (F100, F80, and F60) and three irrigation levels (I100, I80, and I60) in 2018 and repeated again in 2019. The results showed higher soil available K, endogenous hormone contents, antioxidant enzyme activities, photosynthetic rate, and tomato yield, lower lipid peroxidation, and better root morphology and tomato quality in the F80I80 treatment. Compared with the other treatments, the F80I80 treatment increased tomato yield by 5.3–18.1 %, vitamin C content by 7.3–26.6 %, leaf rubisco activity from the fruit enlargement stage to the fruit ripening stage by 4.7–18.1 %, and photosynthetic rate by 4.5–17.8 %. Adjusting PCPC application rate and irrigation level to meet tomato growth requirements could not only save water and fertilizers, but also increase tomato yield and protect the environment.