NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW 2568, Australia.
NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW 2568, Australia.
Sci Total Environ. 2021 Feb 25;757:143790. doi: 10.1016/j.scitotenv.2020.143790. Epub 2020 Nov 27.
In dairy grazing systems, livestock urine patches are hotspots that contribute to global warming, both directly through nitrous oxide (NO) emissions, and indirectly, through nitrate leaching. However, under warm-dry temperate environments, NO emission factors (EFs) have not been thoroughly evaluated, accounting for the influence of urinary nitrogen (N) concentration and urine volume, and emissions measurement approach through different urine application methods. Here we quantified and compared NO emissions and EFs on a moderately well-drained sandy loam soil from urine patches established in naturally expanding effective area (NEEA), representing urine volumes of 2, 3 and 4 L m (equivalent to urine -N loadings of 141, 211 and 282 kg N ha), and using the uniformly wetted area (UWA) with urine applied at 10 L m (709 kg N ha), under two different soil moistures (below field capacity, BFC; field capacity, FC). The results showed that cumulative NO emissions in the NEEA urine patches were 0.36-0.52 kg NO-N ha over 146 days (early-winter to late-spring). In the UWA urine patches, cumulative NO emissions were 2.3 times higher at FC (1.96 kg NO-N ha) than BFC (0.87 kg NO-N ha). The EFs were similar between UWA (0.09%) and NEEA (0.07-0.10%) at BFC but were significantly higher (P < 0.05-0.1) in UWA (0.26%) than NEEA (0.09-0.16%) at FC. The EFs in NEEA were not affected by urine-N loadings under BFC and FC, ranging between 0.07 and 0.16%. The relatively high versus low urine-N loadings in NEEA enhanced pasture herbage and N-uptake responses under both soil moistures. However, there were no differences in apparent N-use efficiency (ranging from 27 to 39%) across the treatments. The EFs observed in this study are much lower than the existing Australian cattle urine annual EF of 0.4%, and further examination to determine a more accurate EF for the industry is required.
在奶牛放牧系统中，牲畜尿斑是导致全球变暖的热点，这既直接通过一氧化二氮（N2O）排放，也间接通过硝酸盐淋洗。然而，在温暖干燥的温带环境下，尚未彻底评估 N2O 排放因子（EF），这主要是因为没有考虑尿氮（N）浓度和尿液量的影响，以及通过不同的尿液应用方法进行排放测量的方式。在这里，我们在适度排水良好的沙壤土上量化和比较了自然扩展有效面积（NEEA）中建立的尿斑的 N2O 排放和 EF，NEEA 尿斑的尿斑体积分别为 2、3 和 4 L m（相当于尿-N 负荷分别为 141、211 和 282 kg N ha），以及在两种不同土壤湿度（低于田间持水量（BFC）；田间持水量（FC））下，用 10 L m（709 kg N ha）施用的均匀润湿区（UWA）。结果表明，在 146 天（初冬至春末）期间，NEEA 尿斑中的累积 N2O 排放量为 0.36-0.52 kg NO-N ha。在 UWA 尿斑中，FC（1.96 kg NO-N ha）的累积 N2O 排放量是 BFC（0.87 kg NO-N ha）的 2.3 倍。在 BFC 下，UWA（0.09%）和 NEEA（0.07-0.10%）之间的 EF 相似，但在 FC 下，UWA（0.26%）显著高于 NEEA（0.09-0.16%）（P <0.05-0.1）。在 BFC 和 FC 下，NEEA 中的 EF 不受尿-N 负荷的影响，范围在 0.07 至 0.16%之间。在两种土壤湿度下，NEEA 中相对较高与较低的尿-N 负荷均增强了牧草和氮吸收的响应。然而，处理之间的表观氮利用率（范围为 27-39%）没有差异。本研究中观察到的 EF 远低于澳大利亚现有牛尿的年度 EF 0.4%，需要进一步研究以确定更准确的行业 EF。
