Can nitrogen input mapping from aerial imagery improve nitrous oxide emissions estimates from grazed grassland?

JM Maire*, S Gibson-Poole, Nicholas J Cowan, Dominika Krol, Cathal Somers, Dave S Reay, Ute M. Skiba, RM Rees, Gary J Lanigan, Karl G Richards

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Most nitrogen (N) lost to the environment from grazed grassland is produced as a result of N excreted by livestock, released in the form of nitrous oxide (N2O) emissions, nitrate leaching and ammonia volatilisation. In addition to the N fertiliser applied, excreta deposited by grazing livestock constitute a heterogeneous excess of N, creating spatial hotspots of N losses. This study presents a yearlong N2O emissions map from a typical intensively managed temperate grassland, grazed periodically by a dairy herd. The excreta deposition mapping was undertaken using high-resolution RGB images captured with a remotely piloted aircraft system combined with N2O emissions measurements using closed statics chambers. The annual N2O emissions were estimated to be 3.36± 0.30kg N2O-N ha-1 after a total N applied from fertiliser and excreta of 608± 40kg N ha-1 yr-1. Emissions of N2O were 1.9, 3.6 and 4.4 times lower than that estimated using the default IPCC 2019, 2006 or country-specific emission factors, respectively. The spatial distribution and size of excreta deposits was non-uniform, and in each grazing period, an average of 15.1% of the field was covered by urine patches and 1.0% by dung deposits. Some areas of the field repeatedly received urine deposits, accounting for an estimated total of 2410kg N ha-1. The method reported in this study can provide better estimates of how management practices can mitigate N2O emissions, to develop more efficient selective approaches to fertiliser application, targeted nitrification inhibitor application and improvements in the current N2O inventory estimation.
Original languageEnglish
Pages (from-to)1743-1774
Number of pages32
JournalPrecision Agriculture
Volume23
Early online date21 Jun 2022
DOIs
Publication statusPrint publication - Oct 2022

Keywords

  • Nitrogen
  • Remote sensing
  • UAV
  • IPCC
  • Spatial distribution map
  • Variable rate application
  • IPCC inventory

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