Journal of Soil and Plant Interactions

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Abstract Although nickel (Ni) is known as an essential element for higher plants, the biological effects of this nutrient on growth, yield, and N metabolism of some plants, particularly leafy vegetables, is still unknown. Therefore, this study was carried out to investigate the effects of Ni and urea nutrition on the growth and yield of lettuce (Lactuca sativa L. cv. Baker) and urea accumulation in plant tissues. In this study, nitrogen was supplied from the source of urea or ammonium nitrate at three levels (5, 10 and 20 mM) and Ni was supplied in the form of NiCl2 at two levels (0 and 0.04 µM). The plants were harvested 6 weeks after transplanting and the fresh weight of shoots and roots were determined. The shoots urea concentration and activity of urease enzyme in the leaves were also measured. The results indicated that shoots fresh weight of the urea-fed plants increased with increasing urea concentration in the nutrient solution. Addition of Ni to the nutrient solution significantly promoted the root and shoots fresh weight of urea-fed plants, regardless of N level. Ni nutrition significantly increased the urease activity in the lettuce leaves and as a result, reduced urea accumulation in the shoots and toxicity effects of urea. Therefore, it seems that urea in combination with Ni can successfully be used in production of lettuce in soilless culture systems.

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Abstract In this study, effect of spraying nickel sulfate and urea on reproductive growth, yield and some qualitative characteristics of strawberry fruit were investigated. Rooted daughter plants of strawberry, cv. Pajaro, were grown in 3 L pots in greenhouse of College of Agriculture, Shiraz University. The established plants were sprayed, at 4-5-leaf stage, with nickel sulfate at concentrations of 0, 150, 300 and 450 mg/L and urea at concentrations of 0 and 2 g/L. Some traits such as yield, weight of primary, secondary and tertiary fruits, length: diameter ratio, inflorescence number and number of flowers in each inflorescence, vitamin C, total soluble solids and total acid were recorded. Results showed that 300 mg/L nickel sulfate without urea increased significantly the yield, primary and secondary fruits’ weight and inflorescence number as compared to control. Also, the 300 mg/L nickel sulfate treatment with 2 g/L urea had the highest rate of total acid (0.75%). In general, spraying 300 mg/L nickel sulfate with 2 g/L urea is recommended for increasing the strawberry yield.

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Nickel (Ni) is the most recently discovered essential element for higher plants. But there is limited information about the effect of this element on yield and nitrogen (N) metabolism of different plants. In this research, the interaction of Ni supplement and N source was studied on nitrate accumulation and growth of lettuce (Lactuca sativa L. cv. Baker) in solution culture. In a greenhouse experiment, lettuce plants were exposed to two Ni levels (0 and 0.04 µM in the form of NiCl2) and three N levels (5, 10, and 20 µM in the form of urea and ammonium nitrate). The plants were harvested 6 weeks after transplanting and the fresh weight of shoots and roots, total N concentration, nitrate concentration and Fe content of shoots were determined. The results indicated that shoot and root fresh weight of nitrate-fed plants were higher than urea-fed plants. Ni nutrition significantly enhanced the yield of urea-fed plants. The shoot nitrate concentration in nitrate-fed plants was significantly greater in comparison with urea-fed plants. On the other hand, nitrate concentration in the shoots of lettuce plants decreased significantly with Ni nutrition. Ni supplementation in urea-fed plants increased the shoot Fe content. The shoot concentration of total-N in the urea-fed plants increased with the Ni supplement. While, Ni had no significant effect on shoot concentration of total-N in the nitrate-fed plants. Addition of low levels of Ni to the nutrient solution, particularly to the urea-containing solution, improved the yield of lettuce. In addition, these plant leaves are safer for human consumption because the shoot nitrate content is significantly reduced by application of Ni.

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