Farm-scale carbon and nitrogen fluxes in pastoral dairy production systems using different nitrogen fertilizer regimes
The nitrogen (N) fertilizer application rate (kg ha −1 year −1 ) in pastoral dairy systems affects the flow of N through the soil, plant and animal pools of the system. With better understanding of the magnitude of these pools and their fluxes, dairy systems could be managed to improve N use effici...
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Veröffentlicht in: | Nutrient cycling in agroecosystems 2020-05, Vol.117 (1), p.1-12 |
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Zusammenfassung: | The nitrogen (N) fertilizer application rate (kg ha
−1
year
−1
) in pastoral dairy systems affects the flow of N through the soil, plant and animal pools of the system. With better understanding of the magnitude of these pools and their fluxes, dairy systems could be managed to improve N use efficiency, therefore reducing losses to the environment. A study with three levels of N fertilizer, 0 (N0), 150 (N150) and 300 (N300) kg N ha
−1
year
−1
, was conducted in the Canterbury region of New Zealand from 1 June 2017 till 31 May 2018. Farm measurements, e.g. pasture and milk production, were used to calibrate three different farm-scale models, DairyNZ’s Whole Farm Model, DairyMod, and Overseer
®
. The models were used to extrapolate periodic farm measurements to predictions of carbon (C) and N pools and fluxes on an annual basis. Pasture and milk production per hectare increased from N0 to N300 by 70 and 58%, respectively. There was a concomitant increase in farm-gate N surplus (input–output) of 43%, resulting in predicted increases in N leaching and greenhouse gas emissions of 72 and 67%, respectively. By increasing N fertilizer from 0 to 300 kg N ha
−1
year
−1
, 53% more feed N flowed through the dairy herd with surplus N deposited as urinary N increasing by 49%. Plant uptake and soil immobilization increased by 58 and 343%, respectively, but not enough to avoid substantial increases in leaching and emission losses. Carbon flux through the soil system increased through increased litter and faecal deposition, but with very little C sequestration because of accelerated microbial respiration rates. |
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ISSN: | 1385-1314 1573-0867 |
DOI: | 10.1007/s10705-020-10052-2 |