Abstract
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.
Highlights
Protected culture; growing perishable crops in environment controlled greenhouses, is a move on technology of global horticulture for last many decades
Previous studies on greenhouse tomato has reported a stem thickness of 1cm at the 15 cm below the tip as the standard stem thickness for a properly nourished tomato plant (Ministry of Agriculture-Canada, 2010) but the stem diameter of this experiment did not show significant treatment effect while the treatment means fall within the desirable plant vigour level as specified above
Nutrient status of the 5th leaf of tomato plant were analysed at the end of the vegetative stage and nitrogen percentage of the 5th leaf was not significantly different among N treatments at (p≤ 0.05) and it was 4-5%, within adequate range for tomato (4-5.5%) (Hochmuth et al, 2006)
Summary
Protected culture; growing perishable crops in environment controlled greenhouses, is a move on technology of global horticulture for last many decades. Since its introduction to Sri Lanka in 1997 protected agriculture techniques are being practiced for cultivation of high-value vegetables. Those grown hydroponically, are provided with high levels of inorganic nutrients. Fertigation in soilless culture is a major determinant of the quality and quantity of the greenhouse crop yields (Wijesekara, 2013). Nitrogen (N) is the most important and widely used plant nutrient and the major potential environmental contaminant. Several studies have pointed out that N wastage from soilless cultures is in the range of 1 ton of N ha-1 year-1 in the absence of drainage recycling (Van Noordwijk, 1990). Albert’s fertilizer mixture is the most commonly used fertilizer mixture and coir dust medium is the main crop growing
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