ABSTRACT

We quantified seasonal nitrous oxide (N₂O) emissions and the associated emission factors (EFs) from: (i) winter oilseed rape (WOSR) cultivated under conventional tillage (CT) and strip tillage (ST) at four fertilizer rates (0, 160, 240 and 320 kg N ha⁻¹) in 2014/2015, and (ii) grassland plots receiving no fertilizer (0 kg N ha⁻¹), or mineral nitrogen (67 kg N ha⁻¹), and either cattle or pig slurry (50, 100 and 200 m³ ha⁻¹). Greater fluxes were observed at higher soil temperatures and a higher water filled pore space, suggesting that denitrification was the main source of N₂O-N from the applied fertilizer/slurry. For WOSR, the N₂O EFs ranged from 0.03 to 1.20% with no effect of the cultivation practice on EFs for equal rates of nitrogen fertilizer. Lower EF values were linked to differences in plant growth at individual sites rather than a specific management effect. For the grassland, the N₂O EFs were highly variable, ranging from −0.70 to 0.49%, but were generally the highest in treatments receiving the highest concentrations of slurry. The EF values for WOSR illustrates that the Tier 1 approach for calculating EFs may be inadequate and the identification of site-specific effects can aid in refining N₂O EF inventories. For the grassland plots all the EFs were significantly lower than the IPCC default values. Although the reason(s) for the low EFs with slurry amendments on grassland is not known, ammonia volatilization could decrease the pool of inorganic N that is available to nitrifying bacteria thereby lowering N₂O fluxes.

摘要

我们通过以下方式对季节性的一氧化二氮（N ₂ O）排放量和相关的排放因子（EFs）进行了量化：（i）在常规耕作（CT）和剥离耕作（ST）下以四种肥料速率（0， 160/240和320 kg N ha ^-1），以及（ii）草地上没有施肥（0 kg N ha ^-1）或矿物质氮（67 kg N ha ^-1）的土地，要么是牛，要么是猪浆（50、100和200 m ³  ha ^-1）。在较高的土壤温度和较高的充水孔隙空间中观察到较大的通量，这表明反硝化作用是施用的肥料/泥浆中N ₂ O-N的主要来源。对于WOSR，N ₂氮素水平相同时，O EFs的范围为0.03至1.20％，而耕作实践对EFs没有影响。较低的EF值与各个地点的植物生长差异有关，而不是与特定的管理效果有关。在草地上，N ₂ O EFs变化很大，范围从-0.70到0.49％，但是在接受最高泥浆浓度的处理中，N ₂ O EFs通常最高。WOSR的EF值说明，用于计算EF的方法1可能不充分，确定具体地点的影响可以帮助精炼N ₂O EF库存。对于草原小区，所有EF均明显低于IPCC的默认值。尽管在草地上使用泥浆改良剂导致EFs低的原因尚不清楚，但氨气挥发可以减少可用于硝化细菌的无机氮库，从而降低N ₂ O通量。