ADDITION OF GEL-FORMING HYDROPHILIC POLYMERS TO NITROGEN-FERTILIZER SOLUTIONS

Environmental and economic concerns are causing a search for more effective fertilizer products and improved methods for managing existing fertilizers. This laboratory and greenhouse study was conducted to determine if the addition of gel-forming, hydrophilic polymers to N fertilizer solutions could reduce N leaching loss and increase plant uptake of N. In the first experiment, a solution of urea ammonium nitrate (UAN, 32% N) was mixed with a variety of polymers at three concentrations, band applied to a sandy soil, and leached weekly for six weeks. Nitrogen leaching losses were reduced from 0 to 45% during the first four weeks due to polymer addition, compared with UAN alone. A second experiment examined the addition of various guar (Cyamopsis psoralides DC.)-derived polymers to UAN as a means of reducing N loss and increasing plant growth. Leaching losses were reduced an average of 26, 16, 7, and 7% for the first four weeks following fertilizer application with the addition of polymer. When UAN was applied with some polymers, growth of fescue (Festuca arundinacea L.) was increased as much as 40% and N accumulation increased as much as 50% as contrasted with UAN alone. These experiments indicate that under highly leached conditions, N leaching loss may be temporarily reduced and plant recovery of N increased through use of some gel-forming, hydrophilic polymers.