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The article discusses the potential of enhanced rock weathering to remove carbon dioxide (CO2) from the atmosphere by spreading crushed rocks over agricultural fields. This method could significantly increase the rate of CO2 removal, contributing to reaching net zero emissions. However, accurate measurement of CO2 capture is crucial for effective policy and regulation. The effectiveness of this technique varies depending on factors such as soil type, climate, and the nature of the crushed rock used. Further research is needed to better understand the reactions in soil and improve measurement methods for CO2 removal. [Extracted from the article]

Aside from its use for improving soil properties, biochar is increasingly promoted as a direct nutrient provider for sustainable recycling of waste materials. However, incomplete understanding of the interacting factors that determine P release from biochar may limit the efficiency of P recycling from biochar to soil. In particular, the contrasting pH of biochar and soil need to be considered. In this study, soil‐free biochar (rice [Oryza sativaL.] husk, 700°C) extractions were performed under different pH (4.6–9.9) and extractant conditions to test how solution composition affects biochar P release. When solution pH was in the range of 7.6 to 8.6 and excess Ca was present in the solution or in biochar, P release was low—only 1 to 7% of the total P was released compared with ∼20% under most other conditions. Importantly, we demonstrate that biochar total Ca concentration is closely related to P availability (R2= 0.76) and could be used to predict biochar P release. The results suggest that for maximum P release, low Ca concentrations in biochar and (soil) solution are needed and/or a pH <7.5 at the soil‐biochar interface. This novel understanding will help engineer sustainable biochar fertilizers optimized for P provision. Phosphorus release from rice husk biochar was investigated.Soil‐free extractions were performed at different pH and solution compositions.The lowest P release occurred at pH 7.6 to 8.6 and in the presence of excess Ca.A conceptual model was developed of biochar P release in different soil conditions.Biochars with Ca <1% and/or pH <7.5 are optimal for maximum P release to soil.

Mining, smelting, land applications of sewage sludge, the use of fungicides containing copper (Cu), and other human activities have led to widespread soil enrichment and contamination with Cu and potentially toxic conditions. Biochar (BC) can adsorb several substances, ranging from herbicides to plant‐inhibiting allelochemicals. However, the range of potential beneficial effects on early‐stage plant growth with regard to heavy metal toxicity is largely unexplored. We investigated the ameliorating properties of a forestry‐residue BC under Cu toxicity conditions on early plant growth. Young quinoa plants (Chenopodium quinoa) were grown in the greenhouse in the presence of 0, 2, and 4% BC application (w/w) added to a sandy soil with 0, 50, or 200 μg g−1Cu supplied. The plants without BC showed severe stress symptoms and reduced growth shortly after Cu application of 50 μg g−1and died at 200 μg Cu g−1. Increasing BC concentrations in the growth medium significantly increased the plant performance without Cu toxicity or under Cu stress. At the 4% BC application rate, the plants with 200 μg g−1Cu almost reached the same biomass as in the control treatment. In the presence of BC, less Cu entered the plant tissues, which had reduced Cu concentrations in the order roots, shoots, leaves. The amelioration effect also was reflected in the plant–soil system CO2gas exchange, which showed clear signs of improvement with BC presence. The most likely ameliorating mechanisms were adsorption of Cu to negatively charged BC surfaces and an improvement of the water supply. Overall, BC seems to be a beneficial amendment with the potential to ameliorate Cu toxicity in sandy soils. Further research with a broad spectrum of different soil types, BCs, and crop plants is required.