Conservation Agriculture (CA) was introduced in the 1930s as a soil conservation system to counter the Dust Bowl in the United States. More recently, it has become widely promoted and adopted in Latin America. In Africa, however, adoption rates by small-scale farmers has been slower and more context specific (FAO 2009 1). CA is based on three principles (Richards et al. 2014 2):
- Minimum soil disturbance: Zero tillage is ideal, but the system may involve controlled tillage in which no more than 20 to 25% of the soil surface is disturbed.
- Retention of crop residues or other soil surface cover: Many definitions of CA use 30% permanent organic soil cover as the minimum, but the ideal level of soil cover is site-specific.
- Use of crop rotations: Crop rotation, ideally with legumes, helps reduce build-up of weeds, pests and diseases. Where farmers do not have enough land to rotate crops, intercropping can be used.
Relationship to CSA
CA supports adaptation through reduced risk of rainfall run-off and soil erosion and can help buffer against drought through increased storage of water in the soil profile. This is particularly important in regions where future climates are projected to become drier and/or extreme rainfall events more frequent. CA can mitigate climate change through carbon sequestration in the soil, though this benefit may not be as large on a global level as has been hoped (Richards et al. 2014). 2
CA practices together with best management practices in the rice- and wheat-based cropping systems of South Asia increased productivity substantially whereas the global warming potential intensity decreased. Positive economic returns and less use of water, labor, nitrogen, and fossil fuel energy per unit food produced were also achieved (Ladha et al. 2016). 3
Impacts and lessons learned
In spite of its many positive attributes, CA is not universally applicable and innovative approaches for promotion among small-scale farmers are often required. Possible constraints include:
- Insufficient quantity of residues and the need for crop residues as livestock feed.
- Fertilizers are sometimes necessary as a complement to legume residues in order to increase crop yields and the available quantity of crop residues.
- Weeds are a major challenge in smallholder cropping systems. Many adaptations of CA use herbicides to control weeds.
- While CA can increase yields in the long term, farmers may need to wait 3 to 7 years to see such increases. As with other long-term investments, insecure land tenure presents an additional constraint (Richards et al. 2014). 2
See also several case studies from Africa at http://www.fao.org/agriculture/crops/thematic-sitemap/theme/spi/scpi-home/managing-ecosystems/conservation-agriculture/ca-cases/en/
FAO. 2009. Scaling-up Conservation Agriculture in Africa: Strategy and Approaches. Addis Ababa, Ethiopia: The FAO Subregional Office for Eastern Africa.http://www.fao.org/ag/ca/doc/conservation.pdf This booklet aims at providing the basis for upscaling Conservation Agriculture by addressing the strategy and approaches to engage policy makers and other stakeholders (farmers, agro pastoralists and pastoralists, donors, researchers, extensions and the private sector) in the challenge to move beyond pilot and demonstration plots.
Richards M, Sapkota T, Stirling C, Thierfelder C, Verhulst N, Friedrich T, Kienzle J. 2014. Conservation agriculture: Implementation guidance for policymakers and investors. Climate-Smart Agriculture Practice Brief. Copenhagen, Denmark: CCAFS.https://cgspace.cgiar.org/rest/bitstreams/34456/retrieve Conservation agriculture (CA) can increase resilience to climate change and has the potential to contribute to climate change mitigation. The benefits of CA are highly site- specific. Innovative approaches are needed to overcome barriers for uptake of CA by smallholders.
Ladha JK, Rao AN, Raman A, ..., Noor S. 2016. Agronomic improvements can make future cereal systems in South Asia far more productive and result in a lower environmental footprint. Global Change Biology 22, 1054-1074.http://www.ncbi.nlm.nih.gov/pubmed/26527502
South Asian countries will have to double their food production by 2050 while using resources more efficiently and minimizing environmental problems. Transformative management approaches and technology solutions will be required in the major grain-producing areas that provide the basis for future food and nutrition security. This study was conducted in four locations representing major food production systems of densely populated regions of South Asia. Novel production-scale research platforms were established to assess and optimize three futuristic cropping systems and management scenarios (S2, S3, S4) in comparison with current management (S1). With best agronomic management practices (BMPs), including conservation agriculture (CA) and cropping system diversification, the productivity of rice- and wheat-based cropping systems of South Asia increased substantially, whereas the global warming potential intensity (GWPi) decreased. Positive economic returns and less use of water, labor, nitrogen, and fossil fuel energy per unit food produced were achieved. In comparison with S1, S4, in which BMPs, CA and crop diversification were implemented in the most integrated manner, achieved 54% higher grain energy yield with a 104% increase in economic returns, 35% lower total water input, and a 43% lower GWPi. Conservation agriculture practices were most suitable for intensifying as well as diversifying wheat-rice rotations, but less so for rice-rice systems. This finding also highlights the need for characterizing areas suitable for CA and subsequent technology targeting. A comprehensive baseline dataset generated in this study will allow the prediction of extending benefits to a larger scale.