Environmental Research Centre, Teagasc, Johnstown Castle, Co. Wexford, Ireland.
Groundwater Protection and Restoration Group, University of Sheffield, Sheffield, United Kingdom.
PLoS One. 2019 Jul 23;14(7):e0219479. doi: 10.1371/journal.pone.0219479. eCollection 2019.
From an environmental perspective optimised dairy systems, which follow current regulations, still have low nitrogen (N) use efficiency, high N surplus (kg N ha-1) and enable ad-hoc delivery of direct and indirect reactive N losses to water and the atmosphere. The objective of the present study was to divide an intensive dairy farm into N attenuation capacity areas based on this ad-hoc delivery. Historical and current spatial and temporal multi-level datasets (stable isotope and dissolved gas) were combined and interpreted. Results showed that the farm had four distinct attenuation areas: high N attenuation: characterised by ammonium-N (NH4+-N) below 0.23 mg NH4+-N l-1 and nitrate (NO3--N) below 5.65 mg NO3--N l-1 in surface, drainage and groundwater, located on imperfectly to moderately-well drained soils with high denitrification potential and low nitrous oxide (N2O) emissions (av. 0.0032 mg N2O-N l-1); moderate N attenuation: characterised by low NO3--N concentration in drainage water but high N2O production (0.0317 mg N2O-N l-1) and denitrification potential lower than group 1 (av. δ15N-NO3-: 16.4‰, av. δ18O-NO3-: 9.2‰), on well to moderately drained soils; low N attenuation-area 1: characterised by high NO3--N (av. 6.90 mg NO3--N l-1) in drainage water from well to moderately-well drained soils, with low denitrification potential (av. δ15N-NO3-: 9.5‰, av. δ18O-NO3-: 5.9‰) and high N2O emissions (0.0319 mg N2O l-1); and low N attenuation-area 2: characterised by high NH4+-N (av. 3.93 mg NH4+-N l-1 and high N2O emissions (av. 0.0521 mg N2O l-1) from well to imperfectly drained soil. N loads on site should be moved away from low attenuation areas and emissions to air and water should be assessed.
从环境角度来看，即使遵循当前法规，优化的奶牛养殖系统的氮利用效率仍然较低，氮盈余量（kg N ha-1）较高，并且能够随时向水和大气中输送直接和间接的活性氮损失。本研究的目的是根据这种随时的输送，将一个密集型奶牛养殖场划分为氮衰减能力区。综合并解释了历史和当前的空间和时间多层次数据集（稳定同位素和溶解气体）。结果表明，该农场有四个不同的衰减区：高氮衰减区：其特点是地表水、排水和地下水中的铵氮（NH4+-N）低于 0.23 mg NH4+-N l-1，硝酸盐（NO3--N）低于 5.65 mg NO3--N l-1，位于不完全到适度排水良好、具有高反硝化潜力和低氧化亚氮（N2O）排放的土壤上（平均 0.0032 mg N2O-N l-1）；中氮衰减区：其特点是排水水中的硝酸盐浓度较低，但产生大量的 N2O（0.0317 mg N2O-N l-1），反硝化潜力低于第 1 组（平均 δ15N-NO3-：16.4‰，平均 δ18O-NO3-：9.2‰），位于排水良好至适度排水的土壤上；低氮衰减区 1：其特点是排水水中的硝酸盐含量高（平均 6.90 mg NO3--N l-1），来自排水良好至适度排水的土壤，反硝化潜力低（平均 δ15N-NO3-：9.5‰，平均 δ18O-NO3-：5.9‰），N2O 排放高（0.0319 mg N2O l-1）；以及低氮衰减区 2：其特点是来自排水不良至不完全排水土壤的高 NH4+-N（平均 3.93 mg NH4+-N l-1）和高 N2O 排放（平均 0.0521 mg N2O l-1）。现场的氮负荷应从低衰减区转移，应评估向空气和水的排放。
