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

Environmental and economic concerns are causing a search for more effe ctive fertilizer products and improved methods for managing existing f ertilizers. This laboratory and greenhouse study was conducted to dete rmine if the addition of gel-forming, hydrophilic polymers to N fertil izer solutions could reduce N leaching loss and increase plant uptake of N. In the first experiment, a solution of urea ammonium nitrate (UA N, 32% N) was mixed with a variety of polymers at three concentrations , band applied to a sandy soil, and leached weekly for six weeks. Nitr ogen leaching losses were reduced from 0 to 45% during the first four weeks due to polymer addition, compared with UAN alone. A second exper iment 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, an d 7% for the first four weeks following fertilizer application with th e 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. T hese experiments indicate that under highly leached conditions, N leac hing loss may be temporarily reduced and plant recovery of N increased through use of some gel-forming, hydrophilic polymers.