The effectiveness of foliar spray of urea-Ni complex on yield and nitrogen metabolism of urea-fed lettuce

The aim of this study was to investigate the effects of foliar application of Ni in the form of NiCl2 or urea-Ni complex on growth, yield, and nitrogen metabolism of two commercial lettuce cultivars (Lactuca sativa L. cvs. Conco Istador and Grizzly) in nutrient solution culture containing urea. A group of lettuce plants was received only urea as foliar spray. Another group of plants did not received urea and Ni as foliar spray application. Results showed that foliar application of Ni, regardless of applied source, significantly increased fresh and dry biomass of the lettuce shoots. Foliar application of Ni resulted in significant increase of shoot Ni concentration; although this increase was, in general greater by urea-Ni than by NiCl2. Floiar spray of Ni significantly increased activity of urease and reduced shoot concentration of urea in both lettuce cultivars. Application of Ni reduction of tissue concentration of ammonium (NH4+) by enhancing activity of glumine synthetase (GS). Foliar spray of Ni resulted in reduced concentration of nitrate (NO3-) and ammonium (NH4+) in lettuce shoots. A significant increase in activity of GS was also observed by foliar spray of Ni. According to the results, foliar spray of Ni particularly in the form of urea-Ni complex was effective in improving yield and nitrogen metabolism of urea-fed lettuce.