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Evaluation of calcium ammonium nitrate and urea-based fertilisers applied to grassland in Ireland

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131620284,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Diogenes Luis Antille, Nyncke J. Hoekstra, Maria --- Ernfors, Karl --- Richards, Stanley T.J. Lalor
Keywords:   Urea calcium ammonium nitrate nBTPT fertiliser use efficiency temperate grassland

Abstract. This study investigated the influence of N source and rate, and timing of N application on dry matter yield (DMY), N responses, N uptake and N use efficiency (NUE) in a grass crop. The experiment used three fertiliser treatments: CAN, urea and nBTPT-coated urea (nBTPT-U), three N rates (0 – control, 25, 50 and 75 kg ha-1), and 18 fertiliser application timings. The agronomic performance of urea was lower than CAN in early spring. This included relatively lower N responses, lower relative DMY (90%) and N uptake (85%) which translated in lower NUE (0.45 vs. 0.70 kg kg-1). For N applications later in the spring both urea and nBTPT-U showed relative DMY and NUE which were within ±5% compared with CAN (100%). nBTPT enhanced the overall performance of urea which was shown with increased temperature towards the summer or increased N rates. In the summer, the efficiency of urea was lower than CAN or nBTPT-U in all measured parameters. The variability of urea and nBTPT-U as N-sources for grass was comparable to CAN but DMY with urea was ≤95% that of CAN (100%) at 8 out of the 19 application timings. Increasing the application rate of urea-N to offset its relatively lower efficiency may not be recommended since DMY of urea-N relative to CAN decreased with increased N fertilisation levels. However, with the use of nBTPT this may be possible, but fertiliser choice needs to be based on the relative costs per unit N.

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