Digital nutrient management decision support and environmental footprints of maize intensification: A Randomized evaluation from Nigeria

Agricultural intensification associated with increased use of external inputs, such as inorganic fertilizer is widely considered relevant to improving farm income and welfare of smallholder farmers in Sub-Saharan Africa. The emphasis on increased use of inorganic fertilizer will likely be associated with increased greenhouse gas emissions, especially nitrous oxide, as with the Asian Green Revolution. Yet, traditional agricultural extension systems typically provide generalized ‘blanket’ fertilizer recommendations that are not tailored to the plot-specific growing conditions of individual farmers, which could lead to negative environmental externalities. Within this context, a digital nutrient management decision support tool ‘Nutrient Expert’ has been co-developed in Nigeria to enable the extension system to transition from provision of generalized to plot-specific fertilizer recommendations. Using a three-year randomized controlled trial in northern Nigeria, this paper analyses the impact of farmers’ access to site-specific nutrient management recommendations, provided through the Nutrient Expert tool on environmental sustainability of maize intensification. The primary outcome of interest is global warming potential (greenhouse gas emission per unit maize yield), measured using the Intergovernmental Panel on Climate Change Tier 1 method. The preliminary results show that the provision of tailored recommendations to the treatment group led to a reduction in global warming potential compared with the control group, who were exposed to blanket recommendations. However, the observed effect size is small, and the effect is not statistically significant at the conventional significance levels. A plausible reason could be due to the on average, low fertilizer application rates in the study area compared with the often cited over application of fertilizer in most parts of Asia. Overall,this paper finds weak evidence of the causal effects of farmer-tailored nutrient management extension advice on mitigating the environmental impacts of fertilizer intensification under farmers’ conditions and management in maize-based farming systems of northern Nigeria