Spatially and temporally variable urinary N loads deposited by lactating cows on a grazing system dairy farm

Ahmed, Awais; Sohi, R.; Roohi, Rakhshan; Jois, Markandeya; Raedts, Pieter; Aarons, Sharon R.

doi:10.1016/j.jenvman.2018.03.046

Cited by 4 publications

(1 citation statement)

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“…Therefore, measuring cumulative N 2 O emissions over a full grazing year at the field scale is rarely reported due to the challenging nature of the N 2 O emissions and the lack of large-scale precise measurement instruments. The modelling and prediction of the N 2 O emissions at the field scale is also complicated because of: (i) the heterogeneous distribution of excreta patches of high N concentration (Di & Cameron, 2012;Snow et al, 2017), (ii) excreta patches can overlap which can change the N 2 O emission rates from urine patches (Cichota et al, 2013;Cook & Kelliher, 2016), (iii) the fields considered are often grazed many times each year, (iv) the effect of a single urination on soil can last for several months after deposition and (v) the fate of the nitrogen from excreta strongly depends on the time of deposition (Ahmed et al, 2018;Haynes & Williams, 1993), in relation to climate conditions at urination and the following weeks. The modelled emissions using the excreta maps in this study are likely to be close to the real emissions, although it is difficult to compare it to existing field measurements.…”

Section: Using N Input Mapping To Estimate Cumulative N 2 O Emissionsmentioning

confidence: 99%

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

et al. 2022

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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 ± 0.30 kg N2O–N ha−1 after a total N applied from fertiliser and excreta of 608 ± 40 kg 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 2410 kg 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.

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