Effect of simulated wet spring conditions on the relative efficiency of three forms of nitrogen fertilizer on grassland

Abstract

There is evidence from solution culture studies that ammonium nitrogen is taken up by grass preferentially to NO3-N at low temperatures (Clarkson & Warner, 1979). In addition NH4 ions are less subject to leaching losses or denitrification (Ryden, 1982). It has been speculated therefore that ammonium N could be the best form of nitrogen for early grass, especially in wet springs. Field experiments have studied the efficiency of different nitrogen forms at the first application over a number of years (McAllister et al. 1965; Van Burg, Dilz & Prins, 1982). The yield response has tended to be variable and may have depended on climatic and soil conditions. Investigations of climatic effects on fertilizer efficiency have often necessitated long-term field studies, but it is proposed that the importance of rainfall in particular could be investigated by means of a short-term irrigation experiment. This paper reports such an experiment using irrigation to simulate a wet spring while keeping other conditions the same for all treatments.