Optimization of irrigation and nutrient concentration based on economic returns, substrate salt accumulation and water use efficiency for tomato in greenhouse

To evaluate the effects of different irrigation and nutrient concentration strategy on growth, yield, water use efficiency (WUE), fruit quality and substrate salt accumulation, tomatoes were grown with five different levels of water (W: 50%, 75%, 100%, 125% and 150%) and nutrient concentrations (N: 0.5, 0.75, 1.0, 1.5 and 2.0 times of Hoagland strength(X)). Fruit quality index was determined by normalization of fruit quality parameters. Deficit irrigation at standard concentration of nutrients reduced yields by 17.43% and 15.52% for T-7 (W-75%-N-1.0x) and 49.54%-51.99% for T-8 (W-50%-N-1.0x) during spring-summer (SS) and fall-winter (FW) seasons, respectively. Contents of total soluble solids (TSS), titrable acidity (TA) and sugar acid ratio (SAR) were all increased in water-deficit treatments. T-8 was found to be highest in TSS, TA and SAR except SAR in FW. Over-irrigation with excessive and standard Hoagland nutrient concentration caused non-significant reduction in yield except T-6 (W-125%-N-1.0x) in SS. T-2 (W-100%-N-2.0x) and T-4 (W-100%-N-1.5x) caused more substrate salt accumulation which resulted in significant decrease in yield and WUE. Through economic analysis, over-watering along with excessive nutrients caused profit reductions. Considering water saving, yield and fruit quality through economic analysis, T-7 found to be optimal strategy.