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Understanding & managing N loss pathways : Minimising nitrogen losses to improve use efficiency in summer crops

Bell, M. J., Schwenke, G. D., Lester, D. W., Bell, M. J., Schwenke, G. D. and Lester, D. W. (2016) Understanding & managing N loss pathways : Minimising nitrogen losses to improve use efficiency in summer crops. In: GRDC Adviser Update - 2016, GoondiwindiToowoomba (Wellcamp) and Chinchilla.

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• Over the past 3 years, we have had 6 experiments with isotope-labelled (15N) urea fertiliser in northern NSW and a further 11 in southern Qld, all focussed on measuring the fate of applied N fertilizer in summer sorghum. Normal fertiliser contains 14N so the use of 15N allows us to trace the fate of urea-N applied to the soil from sowing through to harvest. • Between 56 and 93% of the applied N was found in the soil and plant at harvest, with in-season rainfall (both timing and amount) and soil C and N status having a major impact on the seasonal loss potential. • Avoiding unnecessarily high N rates, delaying or splitting N fertiliser so that peak N availability coincides with peak crop N demand and relying on residual N from legume rotations all significantly reduced gaseous N losses from dryland sorghum, although the effectiveness of any management strategy varied with seasonal conditions. • Nitrification inhibitor-coated urea significantly reduced nitrous oxide emissions in all studies, but did not improve grain yields enough to justify the additional cost on an agronomic basis. • Depending on the season, delaying/splitting N applications gave either no yield benefit (dry season) or a significantly greater yield (good in-crop rainfall). Much of the unused N after a dry season remained in the soil and, provided loss events were not experienced during the fallow, significantly benefited the following crop.
As reliance on N fertilizer increases, getting good crop recovery of applied N is essential Crop N recovery is most efficient when N is distributed through the root volume Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum. Ensuring fertilizer N is in the crop or deeper in the soil profile is the best defence against loss Controlled release fertilizers can reduce denitrification but are rarely economic; legume N is effective

Item Type:Conference or Workshop Item (Paper)
Business groups:Crop and Food Science
Keywords:Nitrate denitrification ammonia volatilisation N use efficiency 15N recovery
Live Archive:08 Nov 2017 05:52
Last Modified:03 Sep 2021 16:51

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