Sustainable futures
Conservation agriculture and building climate resilience in Africa
Climate change is already a source of major challenges in many African countries. In particular food and water security are threatened by increased intensity and frequency of both drought and flood seasons. These lead to poor yields or complete crop failure, loss of soil through erosion, and reduced recharge of the vital groundwater supply on which many rural communities are dependent.
Conservation agriculture (CA) is a widely-promoted innovation to make farming systems more robust in a changing climate, and possibly even to reduce the effects of farming on the climate itself. Farmers who practise CA avoid tilling the soil and the disruption of its natural structure which this entails. The soil surface is also kept covered, ideally with crop residues or other plant material, to reduce surface runoff during heavy rainstorms, to avoid high soil temperatures and to improve the organic carbon content of the soil along with its biological activity. In order to reduce pest and disease pressure, the cropping system is also diversified, by rotation or intercropping. In intercropped systems two crops are planted together. For example, a crop like cowpea or soybean, intercropped with maize, will protect the soil surface, provide additional crop residues, promote the nutrient status of the soil through the “fixation” of atmospheric nitrogen by associated bacteria and also provide an additional food source.
There are many examples of the successful application of CA, but there are also substantial gaps in our understanding of it. The CEPHaS (Strengthening Capacity in Environmental Physics, Hydrology and Statistics for Conservation Agriculture Research) project, a collaborative network of scientists in Zimbabwe, Zambia, Malawi and the UK, is funded by the UK Government’s Global Challenges Research Fund (GCRF) to undertake research focused on water in CA systems. Specifically, we are investigating how the CA approach affects both the water supply to the crop and the recharge of groundwater resources under the cropped soil.
The CEPHaS network includes soil scientists, geophysicists, hydrogeologists, agronomists and statisticians, as well as specialists in the development and evaluation of research capacity. The cross-disciplinary nature of the network is unique. For example, soil scientists typically focus on how water infiltrates the soil surface and is distributed in the rooting zone, while hydrogeologists are concerned with the underlying rocks in which groundwater is stored. However, these disciplines must collaborate to understand water in a changing environment in an integrated way. We want to advise policy makers, for example, on whether the adoption of CA has benefits for both food and water security, or requires a trade-off (for example, if increased water storage in the soil and its uptake by crops reduces water flows to greater depths). The collaboration of the hydrogeologists and soil physicists is helped by geophysicists, whose technology allows us to visualize water from the soil surface to depth, and so to understand better how these domains interact in the water cycle.
At sites in Zimbabwe, Zambia and Malawi we have instrumented CA experiments and land which farmers are managing by CA and conventional methods, so as to measure key properties of the soil and groundwater, and to visualize flows between them with a pioneering low-cost and low-power PRIME (Proactive Infrastructure Monitoring and Evaluation) geophysical system developed at the British Geological Survey (BGS). The findings from this work, interpreted with the help of advanced statistical methods and hydrological models, will allow us to quantify and evaluate the effects of CA practices on the soil water supply, the implications of this for food security, and associated trade-offs or benefits with respect to the recharge of groundwater. Agronomists and agricultural economists on the team help to set these findings in the context of local strategies and national policies for food and water security.
"We aim to work as an equitable partnership, in which scientists from the Global North and South can work together respectfully and effectively"
At the time of writing the CEPHaS team is completing the compilation of its data sets, and the development of analytical methods. An exciting period in which we evaluate the results is just beginning. Preliminary results are encouraging. For example, there is some provisional evidence in Zambia that groundwater recharge under CA is larger in absolute terms, and more responsive to rainfall events than it is under conventional management. The project has also generated published outputs on statistical methodology, legacy soil data sets, research capacity and groundwater investigations. We are also engaged with a range of stakeholders (government, civil society, NGO and private sector) to understand better the challenges faced by farmers in these regions due to climate change, and to explain what we are doing, and what we hope to find out.
The CEPHaS team is not focused purely on these scientific objectives, but also on the development of individual and institutional capacity to undertake research at the interface of agriculture, water and the physical environment. This is achieved through training, and attention to institutional structures which help or hinder research capacity. This work is facilitated by the Capacity Research Unit at Liverpool School of Tropical Medicine, who are working with all partners to maximize the impact of project activities on research capacity. We aim to work as an equitable partnership, in which scientists from the Global North and South can work together respectfully and effectively. Such partnership is as important as good scientific method if the goals of mitigating and adapting to climate change are to be achieved.
The CEPHaS project is supported by the Natural Environment Research Council (UK Research and Innovation) as part of the Global Challenges Research Fund [grant number NE/P02095X/1].
Further reading
More information about the CEPHaS project, including briefing documents can be found at its website and its Twitter feed
Banda, K.; Mabvuso, S.; Owen, R.; Mudimbu, D.; Brauns, B.; Lapworth, D. ; Butcher, A.; MacDonald, A. ; Namaona, W.. 2018 Estimation of groundwater recharge due to conservation agriculture practice. [Poster] In: 19th WaterNet/WARFSA/GWPSA Symposium, Livingstone, Zambia, 31 Oct - 2 Nov 2018 http://nora.nerc.ac.uk/id/eprint/524838/
Bates, I, Chabala, L M, Murray Lark, R, MacDonald, A, Mapfumo, P, Mtambanengwe, F, Patson, C, N, Owen, R, Phiri, E, and Pulford, J. 2020. Letter to the Editor: Response to Global soil science research collaboration in the 21st century: Time to end helicopter research by Minasny et al. Geoderma, vol 378. https://doi.org/10.1016/j.geoderma.2020.114559
Chabala, L M, Chimungu, J G, Lark, R M, Mtambanengwe, F, Nalivata, P C, Phiri, E, and Sakala, G M. 2020. Eliciting experts’ tacit models for the interpretation of soil information, an example from the evaluation of potential benefits from conservation agriculture. Geoderma, 376, 114545 https://doi.org/10.1016/j.geoderma.2020.114545
Lark, R M, Ligowe, I S, Thierfelder, C, Magwero, N, Namaona, W, Njira, K, Sandram, I, Chimungu, J G, and Nalivata, P C. 2020. Longitudinal analysis of a long-term Conservation Agriculture experiment in Malawi and lessons for future experimental design. Experimental Agriculture, 56, 506–527. https://doi.org/10.1017/S0014479720000125
Mukumbuta, I, Chabala, L M, Sichinga, S, Miti, C, Lark, R M. 2021. A comparison between three legacy soil maps of Zambia at national scale: The spatial patterns of legend units and their relation to soil properties. Geoderma, 402, 115193 https://doi.org/10.1016/j.geoderma.2021.115193
Pulford J, Crossman S, Begg S et al. Strengthening research management and support services in sub-Saharan African universities and research institutions. AAS Open Res 2020, 3:31 https://doi.org/10.12688/aasopenres.13100.1