The effectiveness of nitrification inhibitor application on grain yield and quality, fertiliser nitrogen recovery and soil nitrous oxide emissions in a legume–wheat rotation under elevated carbon dioxide (FACE)

Abstract

Managing nitrogen (N) supply to better match crop demand and reduce losses will be an important goal under future predicted elevated carbon dioxide (e[CO2]) conditions. This study comprised two Free-Air Carbon dioxide Enrichment (FACE) experiments conducted in southern Australia in 2011. The first experiment (Exp-1) was a field experiment that investigated the impact of a nitrification inhibitor (NI), 3,4-dimethylpyrazole phosphate (DMPP), and supplementary irrigation on utilisation of legume (field pea) residual N by a wheat crop and soil nitrous oxide (N2O) emissions. The second experiment (Exp-2) used 15N techniques in soil cores to investigate the impact of DMPP on recovery of fertiliser N. In Exp-1, grain N concentration increased (by 12%, P < 0.001) with NI application compared with no NI application, irrespective of CO2 concentration ([CO2]) and supplementary irrigation. With NI application the grain N harvest index increased under e[CO2] (82%) compared with a[CO2] (79%). Applying the NI compensated for decreased grain copper concentration observed under e[CO2] conditions. NI had minimal effect on soil N2O emissions in the wheat crop regardless of [CO2]. In Exp-2, 65% (±1 standard error, n = 15) of the applied N fertiliser was recovered in the aboveground plant, irrespective of NI use. The use of a NI in a cereal–legume rotation may help to increase grain N concentration, increase the mobilisation of N towards the grain under e[CO2], and may also help to compensate for decreases in grain copper concentration under e[CO2]. However, use of a NI may not provide additional benefit for productivity or efficiency of N utilisation.