The fate of nitrogen during agricultural intensification in East Africa: nitrogen budgets in contrasting agroecosystems

The intensification of agricultural systems in sub-Saharan Africa (SSA) is necessary to reduce poverty and improve food security but requires increased nutrient applications to smallholder systems. To avoid the negative consequences of intensification that result from many large-scale agricultural systems (e.g., eutrophication), we must better understand how diverse soil systems in SSA will respond to increased fertilizer applications. We tracked nitrogen (N) inputs and outputs in fertilizer trials at two maize (Zea mays)-agroecological regions of contrasting soil type. We measured maize biomass, grain yields, N leaching, and N gaseous losses from a clayey soil in Yala, Kenya, and a sandy soil in Tumbi, Tanzania, with application rates of 0, 50, 75, 100, 150, and 200 kg N ha-1 yr‑1 over multiple years. Using measurements of NO, N2O, NO3-, biomass N, and an 15N enrichment experiment, we show that N budgets in Yala were nearly always negative, meaning more N was exported in yields or lost..., ,