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 NH₄NO₃ (0, 60 and 120?kg?N?ha^?1) on N uptake, N-leaching and indirect N₂O 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 N₂O emissions were calculated from leached N using the emission factor methodology. Results showed accelerated N-leaching (3?C26?kg?ha^?1?season^?1) and N-uptake (10?C92?kg?ha^?1) with N input. Leached N in groundwater had potential to produce emission increments of 0?C94?g N₂O-N?ha^?1?season^?1 on clay soil, and 5?C133?g N₂O-N?ha^?1?season^?1 on sandy loam soil following the application of NH₄NO₃. 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.