Effect of Dung Quantity and Quality on Greenhouse Gas Fluxes From Tropical Pastures in Kenya

Abstract

To improve estimates of agricultural greenhouse gas emissions in sub‐Saharan Africa, we measured over six individual periods of 25–29 days fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) with subdaily time resolution from dung patches of different quality (C/N ratio: 23–41) and quantity (0.5 and 1.0 kg) on a Kenyan rangeland during dry and wet seasons. Methane emissions peaked following dung application, whereas N2O and CO2 fluxes from dung patches were similar to fluxes from rangeland soils receiving no N additions. Greenhouse gas emissions scaled linearly with dung quantity during both seasons. Dung with a low (23) C/N ratio produced up to 10 times more CH4 than dung with a high (41) C/N ratio. Overall, CH4 emission factors (EFs) ranged from 0.001 to 0.042%, lower than those derived in temperate regions. Cumulative CO2 and N2O emissions were similar for all treatments across the different seasons. The N2O EF ranged from 0 to 0.01%, less than 1% of the Intergovernmental Panel on Climate Change Tier 1 default EF (2%) for N2O emissions from dung and urine patches, likely because of the low dung N content (9.7–16.5 g N kg−1 dry matter). However, these results were consistent with the updated cattle dung EF (0.2%) developed for Kenya in 2016/2017 (EF database ID# 422665). In view of the wide range of climates, soils, and management practices across sub‐Saharan Africa, development of robust GHG EFs from dung patches for SSA requires additional studies.

The effects of climate on decomposition of cattle, sheep and goat manure in Kenyan tropical pastures

“…However, the current study was conducted in the tropics where temperature is not per se limiting. Furthermore, the warmer sites received less precipitation and experienced high vapor pressure deficits that caused rapid water loss and crust formation, likely slowing down microbial decomposition of the manure (Zhu et al 2018). This is consistent with Prieto et al (2019) who also found a negative effect of warming and reduced rainfall on litter decomposition in a semi-arid shrubland because of the desiccating effect of warming and decreased water input.…”

“…In addition, a global decomposition experiment by Wall et al (2008) also demonstrated that soil meso-and macrofauna increased litter decomposition rates in temperate and wet tropical climates. Termites and ants are widespread in the soil in Kenya (Markewich et al 2010), and previous studies have reported termites appearing rapidly after dung deposition on rangelands in SSA (Pelster et al 2016;Zhu et al 2018). Through using the fibrous manure material in their mounds, a significant portion of manure applied may be degraded and/or translocated by the soil fauna (Diamond 1998;Markewich et al 2010).…”

Improving Assessments of the Three Pillars of Climate Smart Agriculture: Current Achievements and Ideas for the Future

“…The latter is still far away though, but the idea is that mitigation successes can from now on not only be identified but also reliably be quantified. Recent work tries to improve on the generic IPCC emission factors as most were developed on estimates derived for systems in developed countries, which are likely not transferable to low and middle income countries given significant differences in management intensity, climates, soils, or even often animal breeds (e.g., Pelster et al, 2017;Goopy et al, 2018;Ndung'u et al, 2018;Richards et al, 2018;Zhu et al, 2018Zhu et al, , 2020. Currently, individual agricultural practices and technologies need to be similarly assessed in terms of meeting simultaneously the demands of pillars 1 and 2.…”

“…The colors indicate to which extent the different aspects elaborated in Figure 1 are addressed. quantifications by Pelster et al, 2016;Goopy et al, 2018;Richards et al, 2018;Zhu et al, 2018). All assessment tools focus on short-term evaluations of GHG emissions, with only soil carbon focused tools being able to assess trends of changes in soil carbon stocks and, thus, CO 2 emissions over time.…”

Soil carbon dioxide and methane fluxes from forests and other land use types in an African tropical montane region

“…Sampling in the morning hours has been shown to minimise the effect of soil temperature in soil respiration (Jian et al 2018). Research in forests and in rangelands in Kenya showed a negligible effect of soil temperature on CH 4 fluxes (Werner et al 2007;Zhu et al 2018). Fluxes were calculated using linear regression between the time of chamber deployment and the change in gas concentrations.…”