Nitrogen leaching and indirect nitrous oxide emissions from fertilized croplands in Zimbabwe

Agricultural efforts to end hunger in Africa are hampered by low fertilizer-use-efficiency exposing applied nutrients to losses. This constitutes economic losses and environmental concerns related to leaching and greenhouse gas emissions. The effects of NH 4 NO 3 (0, 60 and 120 kg N ha −1 ) on N uptake, N-leaching and indirect N 2 O emissions were studied during three maize ( Zea mays L.) cropping seasons on clay (Chromic luvisol) and sandy loam (Haplic lixisol) soils in Zimbabwe. Leaching was measured using lysimeters, while indirect N 2 O emissions were calculated from leached N using the emission factor methodology. Results showed accelerated N-leaching (3–26 kg ha −1 season −1 ) and N-uptake (10–92 kg ha −1 ) with N input. Leached N in groundwater had potential to produce emission increments of 0–94 g N 2 O-N ha −1 season −1 on clay soil, and 5–133 g N 2 O-N ha −1 season −1 on sandy loam soil following the application of NH 4 NO 3 . In view of this short-term response intensive cropping using relatively high N rate may be more appropriate for maize in areas whose soils and climatic conditions are similar to those investigated in this study, compared with using lower N rates or no N over relatively larger areas to attain a targeted food security level.