Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Kreuzeckbahnstr, 19, 82467 Garmisch-Partenkirchen, Germany; Mazingira Centre, International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi 00100, Kenya.
Mazingira Centre, International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi 00100, Kenya.
Sci Total Environ. 2021 Mar 20;761:143184. doi: 10.1016/j.scitotenv.2020.143184. Epub 2020 Oct 27.
Dung and urine patches on grasslands are hotspots of greenhouse gas (GHG) emissions in temperate regions, while its importance remains controversial for tropical regions as emissions seem to be lower. Here we investigated NO, CH and CO emissions from urine and dung patches on tropical pastures in Kenya, thereby disentangling interactive and pure water, dung or urine effects. GHG fluxes were monitored with automated chambers for 42-59 days covering three seasons (short rainy season, long rainy season, dry season) for six treatments (Control; +1 L water; +1 kg dung; 1 L urine; 1 L water +1 kg dung; 1 L urine +1 kg dung). Cumulative CO emissions did not differ among treatments in any of the seasons. Water or urine addition alone did not affect CH fluxes, but these were elevated in all dung-related treatments. Scaled up on the total area covered, dung patches halve the CH sink strength of tropical pastures during the dry season, while during the rainy season they may turn tropical pastures into a small CH source. For NO, both dung and urine alone and in combination stimulated emissions. While the NO emission factor (EF) from dung being constant across seasons, the EF for urine was greater during the short rainy season than during the dry season. Combined application of urine + dung was additive on EF. While the mean dung EF in our study (0.06%) was similar to the IPCC Guidelines for National GHG Inventories EF for dry climate (0.07%), the urine EF we measured (0.03-0.25%) was lower than the IPCC value (0.32%). In addition, the IPCC Guidelines assume a urine-N: dung-N ratio of 0.66:0.34, which is higher than found for SSA (<0.50:0.50). Consequently, IPCC Guidelines still overestimate NO emissions from excreta patches in SSA.
草原上的粪便和尿液斑是温带地区温室气体（GHG）排放的热点，而在热带地区，由于排放似乎较低，其重要性仍存在争议。在这里，我们研究了肯尼亚热带牧场上尿液和粪便斑的 NO、CH 和 CO 排放，从而区分了相互作用和纯水、粪便或尿液的影响。使用自动化室监测 GHG 通量 42-59 天，覆盖三个季节（短雨季、长雨季、旱季），有六种处理方法（对照；+1 L 水；+1 kg 粪便；1 L 尿液；1 L 水+1 kg 粪便；1 L 尿液+1 kg 粪便）。在任何季节，单独添加水或尿液都不会影响 CH 通量，但在所有与粪便相关的处理中，这些通量都会升高。按总覆盖面积计算，旱季粪便斑使热带牧场的 CH 汇强度减半，而雨季热带牧场可能成为 CH 的小源。对于 NO，单独使用粪便和尿液以及两者结合都会刺激排放。虽然粪便的 NO 排放因子（EF）在整个季节保持不变，但在短雨季，尿液的 EF 大于旱季。尿液+粪便的联合应用在 EF 上是相加的。虽然我们研究中的平均粪便 EF（0.06%）与《温室气体国家清单编制指南》为干旱气候规定的 EF（0.07%）相似，但我们测量的尿液 EF（0.03-0.25%）低于《IPCC》值（0.32%）。此外，《温室气体国家清单编制指南》假设尿液-N：粪便-N 比为 0.66:0.34，这高于 SSA 的发现（<0.50:0.50）。因此，《IPCC 指南》仍然高估了 SSA 排泄物斑的 NO 排放。
