Considered a well-known carbon sequestration method, terrestrial enhanced rock weathering (ERW) involves the application of crushed silicate-bearing minerals to urban and agricultural soils. Once dissolved in a soil–water system, alkaline minerals adjust the pH in a range favorable for pedogenic carbonate formation and, hence, atmospheric carbon drawdown. As a fast-weathering Ca-rich mineral, wollastonite is recognized as a primary candidate for this process. Although previous studies have demonstrated the potential of wollastonite to sequester carbon in croplands, no study has investigated the fate of wollastonite over the vertical profile of soil. Furthermore, no studies have investigated changes in the elemental composition of soils due to wollastonite amendment at the field scale. The present study presents the results of multiyear sample collection from different layers (0–15, 15–30, and 30–60 cm) of agricultural soil amended with wollastonite in Woodstock, Ontario, Canada. The impact of initial soil pH on pedogenic carbonate formation was also investigated through the inclusion of two more field trials (Thorndale and Dawn-Euphemia, Ontario). The results indicated that wollastonite addition increased the inorganic carbon pool of the soil to 0.55 t CO 2 /(ha·month) at higher (20 t/ha) wollastonite dosages. The mineralogical analyses indicated the occurrence of weathering in the soil samples, as mineral phases belonging to the weathering products were identified in the treated samples. Furthermore, elemental composition analyses revealed increases in the Ca (0.05–0.32 %) and Mg (0.01–0.02 %) contents in the amended samples. This study indicates that carbonate formation is not limited to surficial layers and that deeper layers also need to be taken into account when estimating carbon capture due to ERW practices.

Monitoring soil organic carbon (SOC) content is crucial for understanding the role of agricultural soils in carbon sequestration and climate change mitigation. However, the influence of sampling frequency on the accuracy of SOC content trends remains an open question. This study investigates the effect of different sampling intervals using soils from the Danish long-term Soil Monitoring Network (SMN), which includes both decadal (every 10–12 years) and more frequent (7–11 times over 30 years) sampling since 1986, where the latter samples were originally collected (and archived) for analysis of soil mineral nitrogen. Our results show that decadal sampling effectively captures long-term SOC content trends, with no significant differences compared to more frequent sampling. Year-to-year variability in SOC content was high, suggesting that short-term fluctuations may mask long-term trends. This variability is reduced when SOC content trends are analysed over multi-year periods. To balance resource limitations with the need for temporal resolution, we suggest that a 3–5 year sampling scheme could be implemented, where a subset of SMN sites is sampled each year. This approach would provide finer temporal detail without the cost and effort of annual monitoring, while maintaining the ability to detect meaningful trends in SOC content dynamics. From an operational perspective, a rotational or rolling sampling strategy where only a fraction of sites (e.g., 20–30 %) are sampled each year such that all sites are eventually sampled in the monitoring period, would also help to maintain continuity of field expertise and laboratory capacity, ensuring consistent data quality over time. • No significant difference in long-term SOC trends between sampling frequencies. • Subsoil (25–50 cm) showed more consistent SOC trend increase than topsoil (0–25 cm). • SOC trends for data at one year apart showed high variability within each site. • The variability was reduced when SOC trends over multiple years were derived.

Alpine soils are globally threatened and are particularly vulnerable to the impacts of climate change. In Australia, development and grazing put further pressure on alpine ecosystems. Consequently, land managers and restoration practitioners are increasingly interested in understanding how to tailor revegetation approaches to enhance their success in mountain environments. Because of the intrinsic role of soils in plant-water relationships, the aim of this study was to quantify and compare the physical and hydraulic properties of soils in the Australian Alps. We investigated four common soils that occur across the Australian Alps bioregion: peat soils (organosols), alpine humus soils, skeletal mountaintop soils, and disturbed soils (anthroposols). We quantified and compared soil bulk density, particle density, porosity, water content, infiltration, hydraulic conductivity, and wilting point between soils. We found significant differences in soil properties both within and among each soil, highlighting the importance of understanding local edaphic conditions to improve revegetation outcomes. We recommend that direct measurements of plant establishment, growth, and survival are linked with soil physical, chemical, and hydraulic properties in future research, to build upon these findings.

As a source of exogenous organic matter, pulp and/or paper mill sludges (PPMS) may have beneficial effects on crop productivity and soil chemical and physical properties. This study's aim was to assess the impacts of two different PPMS materials on crop yields, the quality of percolation water, and soil chemical and hydraulic properties in a three-year field experiment on a silt loam soil in East Central Finland. Fresh (FPMS) and lime-stabilized (LPMS) sludges were applied once at rates of 21–28 fresh-Mg ha−1 in the spring prior to the sowing of grass ley under barley as a cover crop and incorporated into the upper 7 cm soil layer. Supplemental nitrogen (N) was applied at levels of 40 and 80 kg ha−1. A decrease of barley grain yield due to N immobilization was observed at the N level 40 kg ha−1, but the standard N application rate (80 kg ha−1) connected with a moderate C:N ratio (FPMS 27:1, LPMS 24:1) was adequate to avoid significant yield losses. In the second and third year following the PPMS applications, there was a tendency for positive residual effects on the total dry matter yield of grass ley, which could be attributed to slow mineralization of sludge-N. The application of LPMS increased the pH in surface soil by 0.5–0.7-units and Ca concentration by 240–660 mg L−1 of soil relative to the non-amended control over the study period. In the year of PPMS applications, the amendments produced a significant increase (about 2.0 g kg−1) in the total carbon (C) concentrations in the uppermost 10 cm soil layer relative to the non-amended soil. During the following years, the change in soil C was no longer measurable, indicating relatively fast decomposition of sludge-C. Saturated hydraulic conductivity tended to be 1.4 to 2.3 times higher in the PPMS-treated soils than in the non-amended soil. Except for the decline in readily plant-available water, the other common water retention parameters were not significantly affected by the PPMS amendments. There were significant positive treatment effects on the amount of water retained between −13 and − 316 kPa matric potentials, suggesting an increase in medium-sized pores contributing to water storage in the soil. To maintain or enhance the beneficial direct and indirect effects of PPMS on crop yields and soil physico-chemical properties, repeated applications of PPMS are required, possibly combined with the use of organic fertilizers, especially during grass ley years.

Understanding how long-term land use affects soil quality and resistance to degradation is essential for identifying sustainable management practices in different soil types. This study's aim was to evaluate how different fertilization approaches influence soil aggregate stability (SAS) and some associated soil properties. The experiment was established in 1955 at three sites with different soil types (Chernozem on loess, Phaeozem on loess, and Cambisol on gneiss) and diverse climatic conditions. Three fertilization scenarios were selected for the study conducted during 2014–2021: i) farmyard manure (40 t ha−1) once every 4 years; ii) NPK mineral fertilizer every year plus farmyard manure once every 4 years, and iii) no fertilizer (control).Farmyard manure positively affected stability of the Cambisol soil aggregates in both cases of fertilization (i and ii). On the other hand, manure had negligible impact upon SAS of the other two soils. In addition, significantly lower SAS values were measured for soils fertilized also by the mineral fertilizer (ii) than for the other scenarios (i and iii). Manure treatment and combined fertilization showed a significant increase in hot water extractable carbon and total carbon content at all sites compared to the unfertilized treatments. A positive relationship between SAS and total organic carbon was confirmed, however, only for the Cambisol spring samples. In some years, composition of organic matter or content of glomalin was also investigated to reveal their effects on SAS. A positive impact of hydrophobicity on SAS was proven for the Phaeozem and Chernozem, but not for the Cambisol. An unexpected negative effect was observed for glomalin. For both spring and summer sampling events, the SAS values were strongly and negatively correlated with the field (sampling) soil water content, which partly masked effects of other soil properties on SAS. These results underscore the importance of complex long-term studies for understanding mutual interactions affecting the stability of soil aggregates in individual soil types and different climatic conditions.