Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland.
Finnish Meteorological Institute, Helsinki, Finland.
PLoS One. 2023 Aug 10;18(8):e0284092. doi: 10.1371/journal.pone.0284092. eCollection 2023.
Organic soil amendments are used to improve soil quality and mitigate climate change. However, their effects on soil structure, nutrient and water retention as well as greenhouse gas (GHG) emissions are still poorly understood. The purpose of this study was to determine the residual effects of a single field application of four ligneous soil amendments on soil structure and GHG emissions. We conducted a laboratory incubation experiment using soil samples collected from an ongoing soil-amendment field experiment at Qvidja Farm in south-west Finland, two years after a single application of four ligneous biomasses. Specifically, two biochars (willow and spruce) produced via slow pyrolysis, and two mixed pulp sludges from paper industry side-streams were applied at a rate of 9-22 Mg ha-1 mixed in the top 0.1 m soil layer. An unamended fertilized soil was used as a control. The laboratory incubation lasted for 33 days, during which the samples were kept at room temperature (21°C) and at 20%, 40%, 70% or 100% water holding capacity. Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes were measured periodically after 1, 5, 12, 20 and 33 days of incubation. The application of ligneous soil amendments increased the pH of the sampled soils by 0.4-0.8 units, whereas the effects on soil organic carbon content and soil structure varied between treatments. The GHG exchange was dominated by CO2 emissions, which were mainly unaffected by the soil amendment treatments. The contribution of soil CH4 exchange was negligible (nearly no emissions) compared to soil CO2 and N2O emissions. The soil N2O emissions exhibited a positive exponential relationship with soil moisture. Overall, the soil amendments reduced N2O emissions on average by 13%, 64%, 28%, and 37%, at the four soil moisture levels, respectively. Furthermore, the variation in N2O emissions between the amendments correlated positively with their liming effect. More specifically, the potential for the pulp sludge treatments to modulate N2O emissions was evident only in response to high water contents. This tendency to modulate N2O emissions was attributed to their capacity to increase soil pH and influence soil processes by persisting in the soil long after their application.
有机土壤改良剂用于改善土壤质量和缓解气候变化。然而，它们对土壤结构、养分和水分保持以及温室气体（GHG）排放的影响仍知之甚少。本研究的目的是确定单一田间施用四种木质土壤改良剂对土壤结构和 GHG 排放的残留影响。我们使用来自芬兰西南部 Qvidja 农场正在进行的土壤改良田间试验的土壤样本进行了实验室培养实验，这是在单一施用四种木质生物质两年后进行的。具体来说，我们使用了两种通过慢速热解生产的生物炭（柳树和云杉），以及两种来自造纸工业侧流的混合纸浆污泥，施用量为 9-22 Mg ha-1，混入 0.1 m 表层土壤中。未施肥的土壤作为对照。实验室培养持续了 33 天，在此期间，样品保持在室温（21°C）和 20%、40%、70%或 100%的水分保持能力下。在培养 1、5、12、20 和 33 天后定期测量二氧化碳（CO2）、氧化亚氮（N2O）和甲烷（CH4）通量。施用木质土壤改良剂将采样土壤的 pH 值提高了 0.4-0.8 个单位，而对土壤有机碳含量和土壤结构的影响因处理而异。温室气体交换主要由 CO2 排放主导，土壤改良处理对 CO2 排放几乎没有影响。与土壤 CO2 和 N2O 排放相比，土壤 CH4 交换的贡献可以忽略不计（几乎没有排放）。土壤 N2O 排放与土壤水分呈正指数关系。总体而言，土壤改良剂分别在四个土壤水分水平下平均减少了 13%、64%、28%和 37%的 N2O 排放。此外，N2O 排放的变化与改良剂的石灰化效应呈正相关。更具体地说，只有在高含水量下，纸浆污泥处理对调节 N2O 排放的潜力才明显。这种调节 N2O 排放的趋势归因于它们增加土壤 pH 值的能力，并通过在施用后长时间留在土壤中而影响土壤过程。
