The impact of site-specific soil-test-based extension advice on farm management in Malawi

Agricultural extension services in Africa face many challenges in reaching farmers with information for sustainable and improved crop production. A critical gap for many smallholders is a lack of knowledge of their soils, including soil organic carbon (SOC) content, a key soil health indicator driving fertiliser responsiveness and crop production. We use a randomised control trial (RCT) to estimate the causal effects of real-time diagnostics and soil carbon measurement to support behavioural change and farmers’ adaptive capacity to improve farm management practices. Treatment group farmers receive context-specific extension services through site-specific soil tests using a handheld reflectometer as a starting point for in-depth discussions with extension agents about soil management. The results suggest significant improvements in sustainable intensification within the treatment group, with gains in farmer experimentation and adoption of organic inputs and management practices in both the year of advice and one year later. Treatment farmers are 40 percent more likely to apply organic fertilisers, 18 percent more likely to incorporate crop residues into their soils, and 7 percent more likely to intercrop maize with a legume. Further, treatment farmers show better timing of inorganic fertiliser applications, though use decisions are largely unchanged. The widespread fertiliser subsidy program may have influenced this last finding. This research demonstrates that a low-cost soil testing tool combined with individualised soil management advice can influence farmers’ soil nutrient-management behaviours and improve the capacity of extension to deliver site-specific soil information. This can lead to marked improvements in the effectiveness of farm management practices and agricultural extension services.