Interaction effects of nitrogen and irrigation water on yield and water and nitrogen use efficiency of tomato in Bushehr province

There are a separate and combined effects of nitrogen and water, as most important factors, on plant growth. This experiment was conducted to optimize the use of these inputs in drip-irrigated tomatoes to gain optimum quantitative and qualitative yield. The experimental design was RCBD as split manner with three replications in three years. Three irrigation treatments: 75, 100 and 125 percent of calculated irrigation water (IW), and four rates of nitrogen: 0, 75, 150 and 225 kgha-1 N were as main and subplot, respectively. The results showed that effects of each factor on yield, irrigation water use efficiency (IWUE) and nitrogen use efficiency (NUE) was induced by the other one. In treatments of 75%, 100% and 125% of IW, maximum yield, IWUE and NUE obtained from 75, 150 and 225 kgha-1 nitrogens, respectively. Increasing in water rates decreased IWUE in the absence or low rate of N, but increased it in presence of high rates of this nutrient. Although nitrogen application was associated with reduction in NUE, but high water rates improved it. Increasing in mean weight, vitamin C and nitrate concentration of the fruit were obvious by increasing in water and nitrogen rates. Fruit TSS was increased by N application and decreased by increasing water. It was concluded that nitrogen use management should be considered for efficient use of irrigation water in different irrigation regimes