Abstract
Nitrous oxide (N2O) emissions from pastures can vary significantly depending on soil and environmental conditions, nitrogen (N) input, as well as the plant’s ability to take up the N. We tested the hypothesis that legume-based N sources are characterized by significantly lower emission factors than mineral N based dairy systems. Therefore, this study monitored N2O emissions for a minimum of 100 days and up to two growing seasons across a gradient of plant species diversity. Emissions were measured from both grazed pastures and a controlled application of urine and dung using the static chamber method. About 90% of the simulated experiments’ accumulated N2O emissions occurred during the first 60–75 days. The average accumulated N2O emissions were 0.11, 0.87, 0.99, and 0.21 kg ha−1 for control, dung, urine patches, and grazed pastures, respectively. The N uptake efficiency at the excreta patch scale was about 70% for both dung and urine. The highest N2O-N emission factor was less than half compared with the IPCC default (0.3 vs. 0.77), suggesting an overestimation of N2O-N emissions from organically managed pastures in temperate climates. Plant diversity showed no significant effect on N2O emission. However, functional groups were significant (p < 0.05). We concluded that legume-containing pasture systems without a fertilizer addition generally appear capable of utilizing nitrogen inputs from excreta patches efficiently, resulting in low N2O emissions.
Highlights
Agriculture is susceptible to climate change, as global food systems are threatened by an increased risk of intra- and inter-annual yield variability due to the less predictable growing conditions [1]
We explored the potential drivers of nitrous oxide (N2 O) emission at the site to better understand the factors affecting N dynamics to inform the development of site-specific mitigation strategies
Dry matter forage production and N uptake approaches showed that water-filled pore space (WFPS) and soil temperature were most related to N O-N emission factors (EFs) within were higher in the diverse prwrch pastures than the binary prwc pastures in2 Experiment 2
Summary
Agriculture is susceptible to climate change, as global food systems are threatened by an increased risk of intra- and inter-annual yield variability due to the less predictable growing conditions [1]. It is a contributor to climate change by greenhouse gas (GHG) emissions. Among the GHGs, nitrous oxide (N2 O) is about 265 times stronger in terms of the global warming potential compared with CO2 [2], as it destroys the ozone layer in the troposphere [3]. Per year [4] and was estimated for the period 2007–2016 to be about 17.0 Tg N year−1 [5]. Agricultural soils are the foremost important contributor to the global anthropogenic. N2 O emissions (about 3.8 Tg N year−1 ) due to the mineral or organic fertilizer application [5]. The excess N results in losses via leaching, volatilization, and N2 O emissions [7]
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