Nitrogen (N) fertilizers are increasingly being used to meet crop demand for the expanding human population. However, historical N-use efficiency (NUE) is low for rice paddy fields compared to upland ecosystems. This study aimed to investigate the fate of N fertilizer and compared NUE under different tillage regimes in a rice-based agroecosystem. A long-term field study of tillage regimes (i.e. flooded paddy field, conventional tillage and ridge tillage) and ¹⁵N isotope tracer methods (in situ and incubation) was used to determine N fertilizer fate and uptake. Nitrogen uptake by rice (which represents NUE) significantly differed between tillage regimes (p < .05). Nitrogen-use efficiency was 31% of applied N fertilizer for ridge tillage, which was the highest among the three tillage regimes, while the lowest NUE occurred for conventional tillage (17%). The soil residual N for ridge tillage was significantly higher (21%), than for the flooded paddy field or conventional tillage. The total gaseous N loss was highest for ridge tillage (28%) and lowest for conventional tillage (17%). Ammonia (NH₃) volatilization accounted for the largest proportion of gaseous loss from N fertilizer for all three tillage regimes. However, the largest loss of applied N was with water (runoff and leaching), where N loss accounted for 20% of applied N for ridge tillage but up to 54% for conventional tillage. Ridge tillage changed the soil micro-topography and water regimes leading to better N conservation. Based on these results, adoption of ridge tillage should significantly improve NUE for rice paddy fields.

中文翻译：

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在稻田土壤中使用垄作提高氮素利用效率

氮 (N) 肥料越来越多地用于满足不断扩大的人口对作物的需求。然而，与高地生态系统相比，稻田的历史氮利用效率（NUE）较低。本研究旨在调查 N 肥的去向，并比较水稻农业生态系统中不同耕作方式下的 NUE。^{对耕作方式（即淹水稻田、常规耕作和垄作）和15} N 同位素示踪方法（原位和孵化）的长期田间研究用于确定氮肥的归宿和吸收。水稻对氮的吸收（代表 NUE）在不同耕作方式之间存在显着差异（p < .05)。垄作的氮利用效率为施氮肥的31%，在三种耕作方式中最高，而常规耕作的NUE最低（17%）。垄作的土壤残留氮显着高于淹水稻田或常规耕作（21%）。垄作的总气态氮损失最高（28%），常规耕作最低（17%）。氨（NH ₃) 在所有三种耕作方式中，挥发占氮肥气体损失的最大比例。然而，施用氮的最大损失是水（径流和淋溶），其中氮损失占垄作施用氮的 20%，而常规耕作则高达 54%。垄作改变了土壤微地形和水分状况，从而更好地保持氮。基于这些结果，采用垄作应显着提高稻田的 NUE。