Leaf nutrient status of tomatoes in coconut coir medium – differences in cultivars, impact on yield and quality
University of Latvia, Institute of Biology, Laboratory of Plant Mineral Nutrition, O. Vaciesa street 4, LV-1004 Riga, Latvia
Coconut coir as an alternative to rockwool is increasingly used as a substrate for soilless hydroponic greenhouse production of tomatoes. However, little is known about the nutrient status of tomatoes in coconut coir, especially under intensive production conditions. The aim of this study was to investigate the nutrient status of different tomato cultivars (orange plum ‘Organza F1’, red cherry ‘Daltary RZ F1’, red large fruit-sized ‘Securitas RZ F1’ and pink large fruit-sized ‘Fujimaru F1’) under industrial greenhouse production, using coconut coir as a substrate to reveal nutrient imbalances, their impact on tomato yield and quality, and cultivar differences. Essential nutrient and leaf SPAD value was detected for the youngest fully developed leaves and the old still vital leaves twice per month from April to August 2020. The total yield, marketable and non-marketable yield was regularly determined. During the crop cycle, the content of most of the nutrients in tomato leaves corresponded to the standard range reported for tomatoes. Only some imbalances were found: all cultivars were characterized by low Zn and high S levels in both young and old leaves. The obtained results identified several differences between the cultivars: cherry tomatoes ‘Daltary’ had significantly higher N, K, Fe and Zn in leaves compared to other cultivars. The lowest N, Fe and Cu were determined for large fruit-sized ‘Securitas’. Regardless of the nutrient status and microclimate conditions, the marketable yield of ‘Daltary’, ‘Organza’ and ‘Securitas’ was almost 100%, indicating on high suitability of these cultivars for hydroponic cultivation in coconut coir.