Foliar application of natural zeolites affects the growth and productivity of processing tomato

Abstract

The foliar application of zeolites has been proven to positively affect plant physiology suggesting that it could improve plant growth, however, this topic has been little studied. Two field trials were carried out (in 2021 and 2022) to study the potential beneficial effect of natural zeolite particle films on processing tomato crops. Natural zeolites i) clinoptinolite + and mordenite (CubZeo) and ii) micronized clinoptinolite (BigZeo) were sprayed onto the plants six times in the central crop cycles. In both trials, BigZeo promoted leaf and fruit dry mass (DM) accumulation, and leaf area from the early crop stage compared to the water-sprayed plants (Control). The final aerial DM of BigZeo plants enhanced more in the year with favourable (+39.2%) (2022) than in that with more stressing thermal conditions (2021) (+12.1%). Concurrently, the marketable yield was improved by + 36% in both years with positive effects also on fruit total soluble solids. Under heat stress, the CubZeo crop showed even lower aerial DM than the Control, however, the marketable yield remained similar due to higher fruit DM and higher incidence of blossom-end-rot (BER) in untreated plants. In 2022, CubZeo promoted DM accumulation, leaf expansion and yield even if to a lesser extent than the BigZeo treatment. In the fruits the concentrations of K, Ca, and Mg rose in zeolite-treated plants. The improved Ca level in the fruits can explain the lower occurrence of BER in the zeolite-treated plants, particularly with CubZeo. Si was observed at the highest level in fruits and stems of BigZeo-treated plants, followed by CubZeo and Control ones. The accumulation of Si could explain the best crop responses elicited by BigZeo, whereas the observed responses did not appear to involve changes in the photosynthetic machinery. However, further and comprehensive investigations are needed to define the zeolite film particle characteristics and the related physiological and nutritional changes in the plants.