Quantifying Environmental Impacts of Agricultural Practices and Food Systems

The use of nitrogen fertilizer is a core strategy to increase crop yields and recapitalizing soil and agroecosystem nutrient stocks in depleted soils of Africa. When nitrogen additions are increased, there are inevitably losses of nitrogen to the environment, regardless of whether mineral or organic fertilizers are used. Unfortunately, there are relatively few measurements of nitrogen dynamics in agricultural ecosystems across sub-Saharan Africa, making it difficult to predict the consequences of large-scale changes in nutrient inputs to these systems. We are currently working to quantify nitrogen losses resulting from application of mineral and organic fertilizers. The research is examining critical questions regarding the fate of the added nitrogen and how management practices affect nitrogen losses to the environment and how ecosystems services (such as clean water) are affected. In this work, we are conducting plot and landscape scale measurements of trace nitrogen gas emissions and nitrate leaching in western Kenya, and expanding measurements to sites in West Africa and Tanzania. We are also employing process-based ecosystem and crop production models to investigate how increased nutrient inputs may affect the movement of nitrogen across different landscapes in sub-Saharan Africa.