Determination of optimum nitrogen concentrations in hydroponics for tomato grown in coir medium in tropical greenhouse

Protected culture is a production technology for growing high-value horticultural crops. Fertigation in soilless culture is a major determinant of the quality and quantity of the greenhouse crop yields. Nitrogen is the widely used plant nutrient in fertigation and also the major potential environmental contaminant. Mismanagement of nitrogen in different growth stages has been reported in literature. Therefore, increasing of nitrogen use efficiency is vitally important for ensuring economic and environmental sustainability of protected culture. This study was conducted to determine optimum rates of nitrogen application for tomato addressing the plant nutrient status and total marketable yield. Tomato plants were fertigated with a progressive array of ten N treatments covering vegetative and reproductive stages. Plant analysis, growth parameters and total harvest were measured to find out the optimum nitrogen requirement. The treatment, supplied with N rates of 50, 60, 90 and 140 mg/plant/day at vegetative, early, middle and late reproductive stages, respectively showed the highest plant response. Thus it was selected as the most appropriate fertigation schedule for tomato grown soilless culture which comparatively increases tomato yield while reducing the cost of fertilizer and environmental hazards associated with excessive use of N fertilizer.