Potassium and iron are the main elements that are of great importance in soilless medium in terms of tomato nutrition. However, the activities of plant nutrients are very complex and changes depending on growing stage, environmental condition and element concentrations in nutrient solution. It is necessary to have more information about the combination of K and Fe in different growing stages in soilless culture. Therefore, this study was carried out to determine the effects of different levels of potassium and iron applications on seasonal changes of plant nutrient concentrations of tomato plant grown in soilless culture. For this purpose, treatments were defined by a factorial combination of three potassium (150, 300 and 450 mg L-1) and three iron levels (1, 2 and 3 mg L-1) with 4 replicates. The leaf samples were taken in two periods [26 November 2006 (fruit set), 15th March 2007 (harvest time)] thereby seasonal changes of plant nutrient concentrations were investigated. The evidences provided by this experiment indicated that the different potassium and iron applications had significant effects on plant nutrient concentration of tomato leaves except P and Mn concentration of 2nd periods. High level of K and Fe applications caused antagonistic effect on nutrient uptake and resulted in imbalance on mineral nutrition of tomato plants. Potassium (K), magnesium (Mg), iron (Fe), zinc (Zn), manganese (Mn) and copper (Cu) concentrations of tomato leaves showed seasonal changes by K and Fe applications. While tomato leaves K, Zn and Mn concentrations were decreasing from fruit set to harvest time, Mg, Fe and Cu concentrations were increased.
Key words: Tomato, perlite, potassium, iron, seasonal changes, plant nutrient.
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