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The application of biochar to improve the quality of saline soils has attracted widespread attention. However, the impact of saline soil amendments with biochar prepared at different pyrolysis temperatures remains unclear. Therefore, we conducted a two-year (2022–2023) field experiment in the Hetao Irrigation District, China, to evaluate the effects of the biochar pyrolysis temperature (C1: 300 °C, C2: 500 °C, and C3: 700 °C) and application rate (T1: 10 t/ha and T2: 20 t/ha) on the soil quality and maize yield. The results indicated that (1) all biochar treatments significantly decreased the soil bulk density and increased the soil porosity; (2) treatment C3T1 significantly increased the soil moisture content and decreased soil salinity. The C3T2 treatment significantly increased the soil's organic carbon content, and the soil's available phosphorus content was greatest in the C1T2 treatment. (3) The maize yield increased linearly with the soil quality index (SQI), which was attributed mainly to improvements in the soil water–salt conditions and increases in the soil organic carbon content. In summary, biochar produced at high pyrolysis temperatures, when applied at a low application rate (C3T1), can result in high corn yields and improve saline soil quality. [ABSTRACT FROM AUTHOR]

Biochar application to soil has the potential to sequester carbon in the long term because of its high stability and large-scale production potential. However, biochar technologies are still relatively new, and the global factors affecting the long-term fate of biochar in the environment are still poorly understood. To fill this important research gap, a global meta-analysis was conducted including 64 studies with 736 individual treatments. Field experiments covered experimental durations between 1 and 10 years with biochar application amounts between 1 and 100 Mg ha−1. They showed a mean increase in soil organic carbon (SOC) stocks by 13.0 Mg ha−1 on average, corresponding to 29%. Pot and incubation experiments ranged between 1 and 1278 days and biochar amounts between 5 g kg−1 and 200 g kg−1. They raised SOC by 6.3 g kg−1 on average, corresponding to 75%. More SOC was accumulated in long experimental durations of >500 days in pot and incubation experiments and 6–10 years in field experiments than in shorter experimental durations. Organic fertilizer co-applications significantly further increased SOC. Biochar from plant material showed higher C sequestration potential than biochar from fecal matter, due to higher C/N ratio. SOC increases after biochar application were higher in medium to fine grain textured soils than in soils with coarse grain sizes. Our study clearly demonstrated the high C sequestration potential of biochar application to agricultural soils of varying site and soil characteristics. [ABSTRACT FROM AUTHOR]

A number of agriculture residues may be used either directly or after suitable treatment as amendments to improve soil quality. Such materials include biochar made of agriculture residues, digestate or elemental sulphur obtained from biogas desulphurisation. The joint use of these materials via pre-incubation may be more advantageous than only mixing prior the application to soil. In this study, digestates were mixed with amendments and incubated for 6 weeks before application to soil in a short-term pot experiment with lettuce (Lactuca sativa). The following treatments were tested: control digestate, digestate + biochar, digestate + elemental sulphur, digestate + biochar + elemental sulphur. The biochar-enriched digestate significantly increased soil microbial biomass, soil C:N, fresh above ground biomass, fresh and dry root biomass. Elemental sulphur-enriched digestate caused highest arylsulfatase and phosphatase, increased urease, microbial biomass in soil and fresh root biomass. Amendment of digestate + biochar + sulphur led to the significantly highest total soil carbon, microbial biomass, β-glucosidase, urease, and increased C:N ratio, arylsulfatase in soil and root biomass. It mitigated the adverse effect of either biochar or elemental sulphur on soil respiration. Properties of digestates were apparently affected by pre-incubation. This approach in digestate fertilizer production may contribute to sustainable farming. [ABSTRACT FROM AUTHOR]

Poultry litter biochar (PLB) is a value-adding soil amendment and an economically sustainable approach that is used to enhance food safety and reduce environmental harm. Poultry litter biochar has promising potential but has been under-examined in regards to carbon (C) sequestration in relation to its type and application rate. The objective of this study was to investigate the effectiveness of PLB in enhancing the C sequestration of acid soils through a short-term incubation experiment. The soil was amended with different materials: PLB (1%, 5%, and 10%) and a control (non-amended). The results indicated that PLB application increased soil C mineralization relative to the control (19–1562%), it significantly increased with an increasing application rate (e.g., increased addition 29, 99, and 172% for 1, 5, and 10% of 400 °C PLB), and the soil C mineralization and applied carbon mineralized (ACM) significantly decreased with temperature (e.g., the cumulative C pool ranges of ACM with 1% PLB, added at pyrolysis temperatures of 200, 300, 400, 500, and 600 °C, were 42.0, 34.4, 19.6, 6.16, and 4.04%, respectively). To assist sustainable soil management and to aid the achievement of multiple sustainable development goals (SDGs), as well as to maximize the benefits of PLB applications and minimize the potential environmental risk, it is suggested that application of PLB, pyrolyzed within 400–600 °C at a rate between 1% to 5%, should be adopted in acidic soils in Taiwan. [ABSTRACT FROM AUTHOR]