Data from: 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 from the system than was added in fertilizer. In Tumbi, however, N
budgets were negative at lower fertilizer levels (0 and 50 kg N ha-1), but
positive at higher fertilizer levels (75 and 200 kg N ha-1). At both
sites, most of the N was lost through maize biomass/grain removal and N
leaching (over 96% of total losses). Gas losses were a minor component of
N budgets. These results highlight the importance of tailoring fertilizer
recommendations to a farm’s specific soil and climatic conditions.
However, on these two contrasting sites, fertilizer additions at or below
50 kg N ha-1 do not lead to major losses of N (via gaseous or leaching)
and may be recommended at a range of sites across SSA soils in maize
agroecosystems.