The effect of the kind of Fe chelate on yielding and quality of greenhouse tomato fruits

A two-year-greenhouse experiment was designed to investigate the effect of four chelates, differing in percentage of Fe content and the kind of Fe bonding ligand: Fe 8 Forte (EDTA+HEEDTA), Fe 9 Premium (DTPA), Fe 13 Top (EDTA) and Librel Fe DP7 (DTPA), on the yield and fruit quality of the ‘Merkury’ F₁ greenhouse tomato cultivar grown in peat substrate. Each of the tested fertilisers was applied in three different doses in order to reach the level of 50, 75 or 100 mg available Fe per 1 dm^-3 of growing medium. In the control treatment the amount of this nutrient was equal to 17.9 mg dm^-3. The tomato was cultivated from transplants on benches in the period from the beginning of April to the end of July.

The highest marketable yield of tomato fruits was obtained from plants fertilised with Fe 9 Premium (DTPA), while the lowest was from the treatment with Fe 13 Top (EDTA) chelate. Both of these sources of iron were equally efficient for the early crop yield, which was significantly higher than that of other tested fertilisers. Irrespective of the Fe source, the most favourable dose of this nutrient for marketable and early fruit yield was 50 mg Fe dm^-3. Both tested factors had little effect on fruit composition. The only exception was a significant drop of vitamin C content in the treatment supplied with Fe 9 Premium and an increment of Na in the case of Fe 13 Top use. The increase of Fe in the growing medium up to 75 and 100 mg dm^-3 adversely affected the amount of P in tomato fruits.