The Influence of Fertilization on Greenhouse Tomatoes Cultivated in Peat Bags System

Abstract

Important factors to be considered for growing tomatoes in order to obtain high and safety yield are variety, system of culture and fertilization. To establish how the fertilization managing can influence both yield and quality of greenhouse tomatoes grown on peat bags system, different doses and types of fertilization (basic and additional) were studied in this experiment. Two Dutch cultivars (Cronos F1 and Menhir F1) with high yield potential were used. Cronos F1 recorded the best early yield (5.87 kg·m -2 ) and Menhir F1 the best total yield (13.06 kg·m -2 ). Foliar fertilization, done with a high K ratio fertilizer (10:5:26), once weekly applied, determined distinct significant efficiencies of early yield and significant efficiencies of total yield. Vitamin C, acidity and total sugar content in the fruit increase with foliar fertilization. None of the nitrate or nitrite values over passed the accepted limits of permission for greenhouse tomatoes. Greenhouse tomatoes grown on peat bags system allows to increase early and total yield in comparison with conventional crop in soil. Because bags contain only a small volume of growth medium, they offer much lower water holding capacity and much lower buffering capacity than most soils regarding both major and minor elements. Therefore it is necessary to monitor continually the nutrient availability in the substrate and to adjust accordingly the composition of feed applied to it. The quantity of nutrients which should be applied also depends on the yield potential of the cultivar and growth conditions. Tomatoes need a continuous and steady supply of nutrients through additional fertilization throughout their life cycle because their vegetative and reproductive stages overlap. Since many experiments have not revealed real differences between the product quality of vegetables grown in soil or hydroponically (Schnitzler and Gruda, 2003) soilless culture in greenhouse may be an alternative to soil culture for high-value vegetable crops including tomatoes. Better tomato fruit quality can be obtained by fertilization measures such as an increase in the concentration of the nutrient solution, or a reduction of nitrate application rates. It is also necessary to adopt appropriate nutrient management practices (use of slow- release fertilizers, split applications, combining of radicular and foliar fertilization) which help to supply nutrients in adequate quantities to just meet crop demand and minimize losses, thus increasing the nutrient use efficiency. The objective of the present study was to evaluate two greenhouse tomato hybrids grown in bags on organic substrate (mostly composed from brown peat) in order to establish how fertilization managing can influence yield and chemical properties of fruit.