期刊
ECOLOGICAL APPLICATIONS
卷 31, 期 6, 页码 -出版社
WILEY
DOI: 10.1002/eap.2368
关键词
ammonia; greenhouse gas emissions; knowledge gaps; leaching; pastoralism; rangelands; savanna
资金
- EU-project Supporting EU-African Cooperation on Research Infrastructures for Food Security and Greenhouse Gas Observations (SEACRIFOG) [730995]
- CGIAR Fund Council
- Australia (ACIAR)
- Irish Aid
- European Union
- International Fund for Agricultural Development (IFAD)
- USAID
- Kingdom of Thailand
- Programme for Climate-Smart Livestock (PCSL) - GIZ
Pastoral systems are the dominant livestock production system in arid and semiarid regions of sub-Saharan Africa. Nitrogen emissions hotspots mainly come from ammonia volatilization and soil nitrogen emissions, with uncertainties in nitrogen loss pathways. Atmospheric nitrogen deposition is the major nitrogen input, while nitrogen losses are primarily from leaching in pastures.
Pastoral systems are the dominant livestock production system in arid and semiarid regions of sub-Saharan Africa (SSA). They are often the only form of agriculture that can be practiced due to unfavorable climate and soil fertility levels that prevent crop cultivation. Pastoralism can have negative impacts on the environment, including land degradation, greenhouse gas emissions and other gases to the atmosphere, soil erosion, water pollution and biodiversity loss. Here, we review the current knowledge on nitrogen (N) cycling, storage, and loss pathways, with an emphasis on identification of N emission hotspots. Our review reports a large uncertainty in the amount of N lost as ammonia from excreta and manure storage, as well as N losses via nitrate and DON leaching. We also found that another major N loss pathway (18%), soil N-2 emissions, has not yet been measured. In order to summarize the available information, we use a virtual pastoral farm, with characteristics and management practices obtained from a real farm, Kapiti Research Station in Kenya. For outlining N flows at this virtual farm, we used published data, data from global studies, satellite imagery and geographic information system (GIS) tools. Our results show that N inputs in pastoral systems are dominated by atmospheric N deposition (similar to 80%), while inputs due to biological nitrogen fixation seems to play a smaller role. A major N loss pathway is nitrogen leaching (nitrate > DON) from pastures (33%). Cattle enclosures (bomas), where animals are kept during night, represent N emissions hotspots, representing 16% of the total N losses from the system. N losses via ammonia volatilization and N2O were four and three orders of magnitude higher from bomas than from the pasture, respectively. Based on our results, we further identify future research requirements and highlight the urgent need for experimental data collection to quantify nitrogen losses from manure in animal congregation areas. Such information is needed to improve our understanding on N cycling in pastoral systems in semiarid regions and to provide practical recommendations for managers that can help with decision-making on management strategies in pastoral systems in semiarid savannas.
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