Department of Soil Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh.
Environ Sci Process Impacts. 2021 Jan 1;23(1):132-143. doi: 10.1039/d0em00374c. Epub 2020 Dec 24.
Nitrogen (N) loss from rice production systems in the form of ammonia (NH) can be a significant N loss pathway causing significant economic and environmental costs. Yet, data on NH fluxes in wetland rice ecosystems are still very scarce which limits the accuracy of national and global NH budgets. We measured the NH fluxes in situ in a wetland rice field and estimated emission factors (EF) under two soil management systems (i.e. conventional tillage, CT and strip tillage, ST); two residue retention levels (i.e. 15%, LR and 40% crop residue by height, HR); and three N fertilization rates (i.e. 108, 144 and 180 kg N ha) in two consecutive years (2019 and 2020). The highest NH peaks were observed within the first 3 days after urea application. The mean and cumulative NH fluxes significantly increased with the increases in N fertilization rates and were 18.5% and 18.6% higher in ST than in CT in 2020 but not in 2019. Overall, the highest mean NH fluxes were in 180 kg N ha coupled with either HR or LR and ST or CT. In 2019, the NH EF was unchanged by any treatments. In 2020, the lower EF was in CT coupled with LR (15%) than all other treatment combinations, where ST with HR showed the highest EF (20%). Likewise, the lowest N rate (108 kg N ha) in ST had the highest NH EF (20%) that was similar to higher N rates (144 and 180 kg N ha) in the same tillage treatment and to 180 kg N ha in CT. Our results highlight that NH fluxes in rice field particularly the effects of ST correlated with higher soil pH and NH content and lower redox potential. Our results highlight that NH fluxes are a potentially large N loss pathway in wetland rice under conventional and decreased soil disturbance regimes.
水稻生产系统中以氨（NH）形式损失的氮（N）可能是一种重要的 N 损失途径，会造成巨大的经济和环境成本。然而，湿地水稻生态系统中 NH 通量的数据仍然非常稀缺，这限制了国家和全球 NH 预算的准确性。我们在湿地稻田中进行了 NH 通量的原位测量，并在两种土壤管理系统（即常规耕作 CT 和条耕 ST）、两种秸秆残留保留水平（即 15%，低秸秆量 LR 和 40%作物秸秆高度 HR）和三种施氮率（即 108、144 和 180 kg N ha）下估算了排放因子（EF）；在两个连续的年份（2019 年和 2020 年）进行了测量。在施用尿素后的头 3 天内观察到 NH 峰值最高。NH 通量的平均值和累积值随着施氮率的增加而显著增加，2020 年 ST 比 CT 高 18.5%和 18.6%，但 2019 年则没有。总体而言，在 2020 年，施氮率为 180 kg N ha 时，与 HR 或 LR 结合使用，或与 ST 或 CT 结合使用，NH 通量最高。在 2019 年，任何处理都没有改变 NH EF。在 2020 年，LR（15%）与 CT 结合使用的 EF 最低，而 HR 与 ST 结合使用的 EF 最高（20%）。同样，ST 中最低的氮用量（108 kg N ha）具有最高的 NH EF（20%），这与同一耕作处理中较高的氮用量（144 和 180 kg N ha）和 CT 中的 180 kg N ha 相似。我们的研究结果表明，稻田中的 NH 通量，特别是 ST 的影响，与较高的土壤 pH 值和 NH 含量以及较低的氧化还原电位有关。我们的研究结果表明，在常规和减少土壤干扰的条件下，NH 通量是湿地水稻中一种潜在的大量 N 损失途径。
