Conservation agriculture (CA) has become a dominant paradigm in scientific and policy thinking about the sustainable intensification of food production in sub-Saharan Africa. Yet claims that CA leads to increasing crop yields in African smallholder farming systems remain controversial. Through a meta-analysis of 933 observations from 16 different countries in sub-Saharan African studies, we show that average yields under CA are only slightly higher than those of conventional tillage systems (3.7% for six major crop species and 4.0% for maize). Larger yield responses for maize result from mulching and crop rotations/intercropping. When CA principles are implemented concomitantly, maize yield increases by 8.4%. The largest yield benefits from CA occur in combination with low rainfall and herbicides. We conclude that although CA may bring soil conservation benefits, it is not a technology for African smallholder farmers to overcome low crop productivity and food insecurity in the short term.
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OECD-FAO Agricultural Outlook 2016–2025 59-95 (OECD, 2016).
Van Ittersum, M. K. et al. Can sub-Saharan Africa feed itself? Proc. Natl Acad. Sci. USA 113, 14964–14969 (2016).
Garnett, T. et al. Sustainable intensification in agriculture: premises and policies. Science 341, 33–34 (2013).
Godfray, H. C. J. & Garnett, T. Food security and sustainable intensification. Phil. Trans. R. Soc. B 369, 20120273 (2014).
Hobbs, P., Sayre, K. & Gupta, R. The role of conservation agriculture in sustainable agriculture. Phil. Trans. R. Soc. B 363, 543–555 (2008).
Pretty, J. & Bharucha, Z. Sustainable intensification in agricultural systems. Ann. Bot. 114, 1571–1596 (2014).
Benites, J. R. & Ashburner, J. E. in Conservation Agriculture: Environment, Farmers Experiences, Innovations, Socio-economy, Policy (eds Garcia-Torres, L. et al.) 139–153 (Kluwer Academic, 2003).
Andersson, J. A. & D’Souza, S. From adoption claims to understanding farmers and contexts: a literature review of Conservation Agriculture (CA) adoption among smallholder farmers in southern Africa. Agric. Ecosyst. Environ. 187, 116–132 (2014).
Kassam, A., Friedrich, T. & Derpsch, R. Global spread of conservation agriculture. Int. J. Environ. Stud. 76, 29–51 (2019).
Thierfelder, C., Matemba-Mutasa, R. & Rusinamhodzi, L. Yield response of maize (Zea mays L.) to conservation agriculture cropping system in Southern Africa. Soil Till. Res. 146, 230–242 (2015).
Giller, K. E., Witter, E., Corbeels, M. & Tittonell, P. Conservation agriculture and smallholder farming in Africa: the heretics’ view. Field Crops Res. 114, 23–34 (2009).
Stevenson, J. R., Serraj, R. & Cassman, K. G. Evaluating conservation agriculture for small-scale farmers in sub-Saharan Africa and South Asia. Agric. Ecosyst. Environ. 187, 1–10 (2014).
Brouder, S. M. & Gomez-Macpherson, H. The impact of conservation agriculture on smallholder agricultural yields: a scoping review of the evidence. Agric. Ecosyst. Environ. 187, 11–32 (2014).
Pittelkow, C. M. et al. Productivity limits and potentials of the principles of conservation agriculture. Nature 517, 365–368 (2015).
Erenstein, O., Sayre, K., Wall, P., Hellin, J. & Dixon, J. Conservation agriculture in maize- and wheat-based systems in the (sub)tropics: lessons from adaptation initiatives in South Asia, Mexico, and Southern Africa. J. Sustain. Agric. 36, 180–206 (2012).
Giller, K. E. et al. Beyond conservation agriculture. Front. Plant Sci. 6, 870 (2015).
Grabowski, P. P., Kerr, J. M., Haggblade, S. & Kabwe, S. Determinants of adoption and disadoption of minimum tillage by cotton farmers in eastern Zambia. Agric. Ecosyst. Environ. 231, 54–67 (2016).
Brown, B., Nuberg, I. & Llewellyn, R. Stepwise frameworks for understanding the utilisation of conservation agriculture in Africa. Agric. Syst. 153, 11–22 (2017).
Dixon, J., Gulliver, A. & Gibbon, D. Farming Systems and Poverty: Improving Farmers’ Livelihoods in a Changing World (FAO, 2001).
Valbuena, D. et al. Conservation agriculture in mixed crop–livestock systems: scoping crop residue trade-offs in Sub-Saharan Africa and South Asia. Field Crops Res. 132, 175–184 (2012).
Frelat, R. et al. Drivers of household food availability in sub-Saharan Africa based on big data from small farms. Proc. Natl Acad. Sci. USA 113, 458–463 (2016).
Findeling, A., Ruy, S. & Scopel, E. Modeling the effects of a partial residue mulch on runoff using a physically based approach. J. Hydrol. 275, 49–66 (2003).
Beare, M. H., Cabrera, M. L., Hendrix, P. F. & Coleman, D. C. Aggregate-protected and unprotected organic matter pools in conventional- and no-tillage soils. Soil Sci. Soc. Am. J. 58, 787–795 (1994).
Tian, G., Brussaard, L. & Kang, B. T. Biological effects of plant residues with contrasting chemical compositions under humid tropical conditions: effects on soil fauna. Soil Biol. Biochem. 25, 731–737 (1993).
Schoenau, J. J. & Campbell, C. A. Impact of crop residues on nutrient availability in conservation tillage systems. Can. J. Plant Sci. 76, 621–626 (1996).
Ranaivoson, L. et al. Agro-ecological functions of crop residues under conservation agriculture: a review. Agron. Sustain. Dev. 37, 26 (2017).
Bussiere, F. & Cellier, P. Modification of the soil temperature and water content regimes by a crop residue mulch: experiment and modelling. Agric. For. Meteorol. 68, 1–28 (1994).
Ratnadass, A., Fernandes, P., Avelino, J. & Habib, R. Plant species diversity for sustainable management of crop pests and diseases in agroecosystems: a review. Agron. Sustain. Dev. 32, 273–303 (2012).
Ball, B. C., Bingham, I., Rees, R. M., Watson, C. A. & Litterick, A. The role of crop rotations in determining soil structure and crop growth conditions. Can. J. Soil Sci. 85, 557–577 (2005).
de Oliveira Ferreira, A. et al. Can no-till grain production restore soil organic carbon to levels natural grass in a subtropical Oxisol? Agric. Ecosyst. Environ. 229, 13–20 (2016).
Tuzzin de Moraes, M. et al. Soil physical quality on tillage and cropping systems after two decades in the subtropical region of Brazil. Soil Till. Res. 155, 351–362 (2016).
Corbeels, M., Cardinael, R., Naudin, K., Guibert, H. & Torquebiau, E. The 4 per 1000 goal and soil carbon storage under agroforestry and conservation agriculture systems in sub-Saharan Africa. Soil Till. Res. 188, 16–26 (2019).
Pleasant, J. M. T., Burt, R. F. & Frisch, J. C. Integrating mechanical and chemical weed management in corn (Zea mays). Weed Technol. 8, 217–223 (1994).
Nichols, V., Verhulst, N., Cox, R. & Govaerts, B. Weed dynamics and conservation agriculture principles: A review. Field Crops Res. 183, 56–68 (2015).
Williams, A. et al. Establishing the relationship of soil nitrogen immobilization to cereal rye residues in a mulched system. Plant Soil 426, 95–107 (2018).
Vanlauwe, B. et al. A fourth principle is required to define conservation agriculture in sub-Saharan Africa: the appropriate use of fertilizer to enhance crop productivity. Field Crops Res. 155, 10–13 (2014).
Rusinamhodzi, L. et al. A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions. Agron. Sustain. Dev. 31, 657 (2011).
Steward, P. R. et al. The adaptive capacity of maize-based conservation agriculture systems to climate stress in tropical and subtropical environments: a meta-regression of yields. Agric. Ecosyst. Environ. 251, 194–202 (2018).
Scopel, E., Da Silva, F. A. M., Corbeels, M., Affholder, F. & Maraux, F. Modelling crop residue mulching effects on water use and production of maize under semi-arid and humid tropical conditions. Agronomie 24, 383–395 (2004).
Todd, R. W., Klocke, N. L., Hergert, G. W. & Parkhurst, A. M. Evaporation from soil influenced by crop shading, crop residue and wetting regime. Trans. ASAE 34, 461–466 (1991).
Thierfelder, C. & Wall, P. C. Effects of conservation agriculture on soil quality and productivity in contrasting agro-ecological environments of Zimbabwe. Soil Use Manage. 28, 209–220 (2012).
Thierfelder, C. et al. How climate-smart is conservation agriculture (CA)? Its potential to deliver on adaptation, mitigation and productivity on smallholder farms in southern Africa. Food Secur. 9, 537–560 (2017).
Herrero, M. et al. Smart investments in sustainable food production: revisiting mixed crop-livestock systems. Science 327, 822–825 (2010).
Nyamangara, J. et al. Effect of conservation agriculture on maize yield in semi-arid areas of Zimbabwe. Exp. Agric. 50, 159–177 (2014).
De Roo, N., Andersson, J. A. & Krupnik, T. J. On-farm trials for development impact? The organisation of research and the scaling of agricultural technologies. Exp. Agric. 55, 163–184 (2019).
Pannell, D. J., Llewellyn, R. S. & Corbeels, M. The farm-level economics of conservation agriculture for resource-poor farmers. Agric. Ecosyst. Environ. 187, 52–64 (2014).
Ngoma, H. Does minimum tillage improve the livelihood outcomes of smallholder farmers in Zambia? Food Secur. 10, 381–396 (2018).
Nyagumbo, I., Mkuhlani, S., Mupangwa, W. & Rodriguez, D. Planting date and yield benefits from conservation agriculture practices across southern Africa. Agric. Syst. 150, 21–33 (2017).
Krupnik, T. J. et al. Does size matter? A critical review of meta-analysis in agronomy. Exp. Agric. 55, 200–229 (2019).
Harris, D. & Orr, A. Is rainfed agriculture really a pathway from poverty? Agric. Syst. 123, 84–96 (2014).
Van Bruggen, A. H. C. et al. Environmental and health effects of the herbicide glyphosate. Sci. Total Environ. 616-617, 255–268 (2018).
Cerdeira, A. L., Gazziero, D. L., Duke, S. O. & Matallo, M. B. Agricultural impacts of glyphosate-resistant soybean cultivation in South America. J. Agric. Food Chem. 59, 5799–5807 (2011).
Kirkegaard, J. A. et al. Sense and nonsense in conservation agriculture: principles, pragmatism and productivity in Australian mixed farming systems. Agric. Ecosyst. Environ. 187, 133–145 (2014).
Bai, S. H. & Ogbourne, S. M. Glyphosate: environmental contamination, toxicity and potential risks to human health via food contamination. Environ. Sci. Pollut. Res. Int. 23, 18988–19001 (2016).
Grieser, J., Gommes, R. & Bernardi, M. New LocClim-the local climate estimator of FAO. Geophys. Res. Abstr. 8, 08305 (2006).
Hedges, L. V., Gurevitch, J. & Curtis, P. S. The meta-analysis of response ratios in experimental ecology. Ecology 80, 1150–1156 (1999).
Greenland, S. & O’Rourke, K. On the bias produced by quality scores in meta-analysis, and a hierarchical view of proposed solutions. Biostatistics 2, 463–471 (2001).
Borenstein, M., Hedges, L. V., Higgins, J. P. & Rothstein, H. R. A basic introduction to fixed‐effect and random‐effects models for meta‐analysis. Res. Synth. Methods 1, 97–111 (2010).
Lajeunesse, M. J. On the meta‐analysis of response ratios for studies with correlated and multi‐group designs. Ecology 92, 2049–2055 (2011).
Duval, S. & Tweedie, R. Trim and fill: a simple funnel-plot–based method of testing and adjusting for publication bias in meta-analysis. Biometrics 56, 455–463 (2000).
Lin, L. & Chu, H. Quantifying publication bias in meta-analysis. Biometrics 74, 785–794 (2018).
Base SAS 9.3 Procedures Guide (SAS Institute, 2011).
This work was implemented as part of the CGIAR Research Programs on Climate Change, Agriculture and Food Security (CCAFS) and Maize, which are carried out with support from the CGIAR Trust Fund and through bilateral funding agreements. The views expressed in this document cannot be taken to reflect the official opinions of these organizations.
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Results of the random-effects model developed to determine the influence of explanatory covariates on the CA to CT yield ratio.
Extended Data Fig. 2 Effect of CA relative to CT on crop grain yield as a function of soil texture for different regimes of average seasonal rainfall at the experimental site.
a, < 400mm; b, 400–800mm; c) 800–1200m and d) > 1200mm. Values are mean effect sizes and error bars show the 95% CI. The number of observations and total number of studies for each category are shown in parentheses. The mean effect sizes were considered significant if the 95% CI does not include 0. The CA effect on yield is significantly lower on medium-texture soils than on coarse- (P<0.005) and fine-textured soils (P<0.02) under the 800–1200mm rainfall regime, and the effect on coarse-textured soils is significantly higher than on medium- (P<0.05) and fine-textured soils (P<0.01) under the >1200mm rainfall regime, determined via paired Student’s t-tests.
Extended Data Fig. 3 Operational forms of no- and reduced tillage employed by smallholder farmers in sub Saharan Africa.
Different operational forms of no- and reduced tillage employed by smallholder farmers in sub Saharan Africa (source: CIRAD and CIMMYT).
Extended Data Fig. 4 Effect of CA relative to CT on crop grain yield as a function of type of reduced tillage in the CA treatment.
Values are mean effect sizes and error bars show the 95% CI. The number of observations and total number of studies for each category are shown in parentheses. The mean effect sizes were considered significant if the 95% CI does not include 0. The CA effect on yield is significantly higher under no-tillage than under minimum tillage (P<0.005) and basins/permanent beds (P<0.05), determined via paired Student’s t-tests.
Extended Data Fig. 5 Effect of CA relative to CT on crop grain yield as a function of type of field trial.
Values are mean effect sizes and error bars show the 95% CI. The number of observations and total number of studies for each category are shown in parentheses. The mean effect sizes were considered significant if the 95% CI does not include 0. The CA effect on yield is significantly (P<0.05) higher in on-farm trials than on-station trials.
Extended Data Fig. 6 Funnel plot on the marginal deviations from the random-effects model added to the average logarithmic yield ratio for maize (as reference, solid vertical line).
The diagonal lines represent the 95% CI limits around the effect size logratio. Each point represents an observation (n=933), open blue circles from on-farm studies (n=605), open red circles from on-station studies (n=328). Skewness TS is -0.03, P=0.67 (all observations), 0.18, P=0.07 (on-farm observations) and −0.26, P=0.05 (on-station observations).
Extended Data Fig. 7 Boxplots of logarithmic weights by the inverse of variance of the individual observations in the on-farm (n = 605) versus on-station (n = 328) studies.
The inverse variance weight is significantly (P<0.0001) smaller in on-farm studies than in on-station studies (paired Student’s t-test).
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Corbeels, M., Naudin, K., Whitbread, A.M. et al. Limits of conservation agriculture to overcome low crop yields in sub-Saharan Africa. Nat Food 1, 447–454 (2020). https://doi.org/10.1038/s43016-020-0114-x
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