Leaf nutrient status of tomatoes in coconut coir medium – differences in cultivars, impact on yield and quality

Summary

This field trial examined the nutrient status of four tomato cultivars grown hydroponically in coconut coir as a rockwool alternative in industrial greenhouse production. Most leaf nutrient levels remained within standard ranges for tomatoes; however, all cultivars exhibited low zinc and elevated sulphur. The cherry tomato cultivar 'Daltary' demonstrated significantly higher leaf nitrogen, potassium, iron and zinc compared to other cultivars, whilst large-fruited 'Securitas' showed the lowest nitrogen, iron and copper. Despite these nutrient variations, three cultivars ('Daltary', 'Organza' and 'Securitas') achieved near-100% marketable yields, suggesting coconut coir is a viable hydroponic substrate for tomato production.

Regional applicability

This research is directly applicable to United Kingdom greenhouse horticulture, as soilless hydroponic production of tomatoes in protected environments is established practice. The findings on coconut coir as a rockwool substitute and cultivar performance under intensive conditions would be relevant to UK commercial growers seeking sustainable substrate alternatives, though cultivar suitability and nutrient management protocols may require localisation to UK greenhouse environments and supply chains.

Key measures

Leaf nutrient concentrations (N, K, P, Ca, Mg, S, Fe, Zn, Cu, B, Mn), leaf SPAD chlorophyll values, total yield, marketable yield, non-marketable yield; sampling from April to August 2020 at twice-monthly intervals

Outcomes reported

The study measured leaf nutrient concentrations (N, K, P, Ca, Mg, S, Fe, Zn, Cu, B, Mn) and SPAD values in four tomato cultivars grown in coconut coir, and assessed total, marketable and non-marketable yield. It identified cultivar-specific nutrient profiles and nutrient imbalances (low Zn, high S across all cultivars) and their relationship to yield and quality.

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