Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, 210037, China.
Environmental Sciences, School of Agriculture and Environment, Massey University, Palmerston North, 4442, New Zealand.
Environ Pollut. 2022 Nov 1;312:120068. doi: 10.1016/j.envpol.2022.120068. Epub 2022 Aug 31.
Raw biochar with high pH possibly stimulated ammonia (NH) volatilization in the agricultural soil. We hypothesized that the modified biochar (MBC) with low pH can synchronically decrease the NH and nitrous oxide (NO) losses. We performed a two-year experiment to clarify how citric acid MBC influence the NH volatilization and NO emission as well as the underlying mechanisms. Two typical paddy soils, i.e., Hydragric Anthrosol and Haplic Acrisol, receiving equal urea N with 240 kg ha but varied rates of MBC with 0, 5, 10, and 20 t ha (named Urea, Urea + MBC5, Urea + MBC10, and Urea + MBC20, respectively) were studied. The results showed that MBC-amended treatments effectively mitigated the NH volatilization from Hydragric Anthrosol and Haplic Acrisol by 29.6%-57.9% and 30.5%-62.4% in 2017, and by 16.5%-21.0% and 24.5%-35.0% in 2018, respectively, compared to Urea treatment. In addition, significantly lower NO emissions with averaged 38.3% and 43.1% in 2017, and 51.7% and 26.7% were recorded under Hydragric Anthrosol and Haplic Acrisol, respectively, following the MBC application (P < 0.05). Increased MBC addition performed higher efficacy on mitigating NH volatilization, particularly in the first rice season, while this "dosage effect" was not found for NO reduction. Lowered pH in overlying water, enhanced adsorption of NH-N and its nitrification rate likely contributed to the lower NH volatilization as result of MBC addition. The nirS and nosZ gene copies were not changed by MBC, while the nirK gene copies were decreased as result of MBC amendment by 8.3%-25.2% under Hydragric Anthrosol and by 21.8%-24.9% under Haplic Acrisol. Consequent lower ratio of nirK/(nirS + nosZ) explained the mitigation effect of MBC on NO emission. In conclusion, the present two-year study recommends that MBC applied at a low dosage can perform positive effect on controlling the nitrogenous gas pollutants from paddy soil.
原始生物炭的高 pH 值可能会刺激农业土壤中的氨（NH）挥发。我们假设低 pH 值的改性生物炭（MBC）可以同时减少 NH 和氧化亚氮（NO）的损失。我们进行了为期两年的实验，以阐明柠檬酸 MBC 如何影响 NH 挥发和 NO 排放以及潜在机制。两种典型的水稻土，即 Hydragric Anthrosol 和 Haplic Acrisol，接受相同的尿素 N（240 kg/ha），但 MBC 的添加率不同（0、5、10 和 20 t/ha，分别命名为 Urea、Urea+MBC5、Urea+MBC10 和 Urea+MBC20）。结果表明，与 Urea 处理相比，MBC 处理在 2017 年有效减少了 Hydragric Anthrosol 和 Haplic Acrisol 中 NH 的挥发，分别减少了 29.6%-57.9%和 30.5%-62.4%，在 2018 年分别减少了 16.5%-21.0%和 24.5%-35.0%。此外，在 Hydragric Anthrosol 和 Haplic Acrisol 中，MBC 处理下分别记录到平均降低 38.3%和 43.1%的 NO 排放，显著降低了 51.7%和 26.7%（P<0.05）。在第一年水稻季，增加 MBC 的添加量对减少 NH 挥发的效果更高，而在减少 NO 方面则没有发现这种“剂量效应”。在覆盖水中降低 pH 值，增强 NH-N 的吸附及其硝化速率可能是由于添加 MBC 导致 NH 挥发降低的原因。MBC 并未改变 nirS 和 nosZ 基因拷贝数，但在 Hydragric Anthrosol 下，MBC 处理使 nirK 基因拷贝数减少了 8.3%-25.2%，在 Haplic Acrisol 下减少了 21.8%-24.9%。因此，nirK/(nirS+nosZ) 的比值降低解释了 MBC 对 NO 排放的缓解作用。综上所述，本两年研究建议，低剂量的 MBC 可以对控制稻田氮气态污染物产生积极影响。
