Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8879082 | Field Crops Research | 2018 | 8 Pages |
Abstract
Enhanced efficiency nitrogen (N) fertilisers (EENFs) contain chemical urease or nitrification inhibitors, or physical barriers (e.g. polymer coating) to minimise the rapid build-up of nitrate (NO3â) in soils. They have the potential to improve N use efficiency and lower N2O emissions from soils. However, evidence of the efficacy of EENFs in warm, wet subtropical conditions is lacking. We therefore developed N response curves (0, 30, 60, 90, 120 and 150â¯kg N ha-1) for urea, polymer coated urea (PCU), 3,4-dimethylpyrazole phosphate (DMPP)-urea (Entec®), N-(n-butyl) thiophosphoric triamide (NBPT)-urea (Green urea®) and a carbon-coated urea (Black urea®) in subtropical, aerobic rice (Oryza sativa L) crops in two fields with contrasting soils (Gleysol and Histosol), and quantified N2O emissions from nil-N and 90â¯kg N ha-1 treatments for all EENFs and urea. In the Gleysol, cumulative in-crop N2O emissions were relatively high (approximately 2â¯kg N2O-N ha-1 season-1 with 90â¯kg N ha-1 applied) with no significant mitigation from any EENFs compared to urea. Grain yield data fitted with an exponential model indicated that 95% of the estimated maximum grain yield (6.8â¯t ha-1 at 14% moisture) was achieved with 81â¯kg N ha-1 for the urea treatment. The yield response curves for all tested EENF products did not differ significantly from the urea-N yield response curve. In the Histosol, cumulative in-crop N2O emissions were negligible (around 0.05â¯kg N2O-N ha-1 season-1), with no significant difference (pâ¯<â¯0.05) between N fertiliser or nil-N treatments, and 95% of the estimated maximum grain yield (5.63â¯t ha-1 at 14% moisture) was achieved with only 11â¯kg N ha-1 for urea. There was no evidence that EENFs could achieve the maximum yield at a lower applied N rate. We hypothesised that the low soil pH of 4.9 (1:5 CaCl2 extract) may have inhibited nitrification in the Histosol, leading to low N2O emissions and a limited response to N fertiliser. Ultimately, the results of this study found no evidence that EENF products could improve agronomic N use efficiency or lower N2O emissions in the two aerobic rice crops studied.
Keywords
Related Topics
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Agricultural and Biological Sciences
Agronomy and Crop Science
Authors
Terry J. Rose, Peter Quin, Stephen G. Morris, Lee J. Kearney, Stephen Kimber, Michael T. Rose, Lukas Van Zwieten,