Effect of potassium magnesium chloride in the fertigation solution as partial source of potassium on growth, yield and quality of greenhouse tomato

The effect of partial replacement of KCl in the fertigation by (KClMgCl2)-Mg-. on growth, yield and quality of greenhouse tomato (cv. Durinta) was studied in a soil-less system. Forty-seven days after planting (DAP), three treatment solutions were applied to the plants using different K sources: (1) KNO3, (2) KCl, and (3) (KClMgCl2)-Mg-. + KCl (25%:75% in terms of K supplied). In both treatments 2 and 3, NH4NO3, Ca(NO3)(2) and HNO3 were added as source of N. Plant height and total chlorophyll were the highest in the KCl + (KClMgCl2)-Mg-. treatment. Leaf Mg content was significantly lower in the KCl treatment, whereas highest in the KCl + (KClMgCl2)-Mg-. treatment. Both KCl and KCl + (KClMgCl2)-Mg-. led to a significantly higher leaf Cl content as compared with the KNO3 treatment, but no Cl toxicity was observed in either treatment. Total yield was not different among treatments. Fruit firmness and freshness of the calyx were significantly improved by KCl and KCl + (KClMgCl2)-Mg-., and the number of rotten and blotchy fruits were significantly reduced by both these treatments. KCl + (KClMgCl2)-Mg-. also led to significantly higher levels of glucose, Mg and dry matter content in the fruit. Lower NO3 and higher Fe contents were measured in both treatments 2 and 3. Although KCl as sole K source showed lower foliar Mg level as compared to KNO3, the use of the KCl in tomato fertigation improved tomato fruit appearance and qualities. However, 25% replacement of KCl by KCl + (KClMgCl2)-Mg-. increased the foliar Mg level and improved fruit qualities even further. (C) 2003 Elsevier B.V. All rights reserved.