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Abstract Understanding spatiotemporal dynamics of nitrogen (N) balance is essential for improving food security and mitigating environmental risks. Yet long-term, high-resolution assessments remain scarce in the Lake Victoria Basin (LVB), despite rising production demands and worsening water quality. In this study, we estimated four major N inputs (fertilizer, manure, atmospheric deposition, and biological fixation) and crop N outputs from 36 species for the period 2000–2020 to calculate nitrogen use efficiency (NUE) and N surplus. Regression and spatial analyses were further conducted to identify the drivers influencing their spatiotemporal patterns. During the two decades, N inputs increased from 10.01 to 17.49 kg N ha −1 (a 75% rise), while N outputs increased from 7.57 to 10.05 kg N ha −1 (33%), leading to a decline in NUE from 76% to 61% and a doubling of N surplus from 3.85 to 8.38 kg N ha −1 . The rising N surplus was mainly driven by greater fertilizer and manure applications, low crop responsiveness to N, cropping patterns, and climatic factors. This first spatially explicit, long-term N balance dataset for the LVB offers insights into N management and regional environmental degradation, supporting targeted strategies to improve productivity and reduce pollution in line with SDG 2 (Zero Hunger) and SDG 6 (Clean Water and Sanitation).
Sun et al. (Tue,) studied this question.