EFFECT OF THE APPLICATION OF MONOSILICIC ACID FERTILIZER ON YIELD AND QUALITY OF GREENHOUSE TRIPLOID WATERMELON

Silicon plays an important role in the structural rigidity of the cell walls. The forms of silicon in the soil are not easily assimilated by plants and only a small proportion is absorbed as H₄SiO₄. It polymerizes when it dehydrates and concentrates on the epidermis cells as biogenic amorphous silicon (SiO₂). Cucurbitaceous are not cumulative silicon plants. They work with a selective assimilation. The percentage of silicon uptake in these plants is small, but their presence can significantly benefit the plant in situations of biotic and abiotic stresses. The objective of the study reported here was to evaluate the effect of monosilicic acid fertilization on the yield and quality of triploid watermelon. The experiment was carried out during 2006 at the UAL-ANECOOP Experimental Farm Foundation located in Almeria (Spain). The greenhouse was the typical low cost plastic greenhouse, Almeria parral-type, with a surface area of 1784 m². The covering material was a 0.2 mm thick tri-layered polyethylene film. The crop was grown on sand-mulched soil (sand-covered soil typical to the region). The cultivar ‘Solinda’ (Citrullus lanatus) triploid watermelon was used. Two fertilizing treatments were used: control (conventional fertilization) and silicon-added (applying besides the conventional fertigation, 250 ml H₄SiO₄•ha^-1). Yield and quality parameters (kg•m^-2; kg per plant, fruits per m², fruits per plant, mean fruit weight and diameter, soluble solids, firmness and acidity of the pulp) were quantified. The monosilicic acid fertilizer had a positive impact on the parameters of fruit quality (°Brix and pulp firmness). The effects of monosilicic acid were detected when the weather began to be warm.