The effects of dunite fertilization on growth and elemental composition of barley and wheat differ with dunite grain size and rainfall regimes

Enhanced weathering (EW) of silicate rocks is a negative emission technology that captures CO2 from the atmosphere. Olivine (Mg2SiO4) is a fast weathering silicate mineral that can be used for EW and is abundant in dunite rock. In addition to CO2 sequestration, EW also has co-benefits in an agricultural context. Adding silicate minerals to soils can significantly improve crop health and growth as the weathering releases elements such as silicon (Si) that can stimulate crop growth and increase stress resistance, a co-benefit that is becoming increasingly important as global warming proceeds. However, dunite also contains heavy metals, especially nickel (Ni) and chromium (Cr), potentially limiting its use in an agricultural context. In this study, we investigate the influence of dunite addition on growth of barley and wheat in a mesocosm experiment. We amended the soil with the equivalent of 220 ton ha-1 dunite, using two grain sizes (p80 = 1020 µm and p80 = 43.5 µm), under two rainfall regimes (each receiving the same amount of 800 mm water y−1 but at daily versus weekly rainfall frequency). Our results indicate that the amendment of fine dunite increased leaf biomass but only with daily rainfall. Aboveground biomass was significantly reduced with weekly rainfall compared to daily rainfall, but this reduction was slightly alleviated by fine dunite application for wheat. This indicates a positive effect of dunite during drying-rewetting cycles. For barley the negative effect of reduced rainfall frequency was not counterbalanced by dunite application. Contrary to our expectations, calcium (Ca) and Si concentrations in crops decreased with fine dunite application, while, as expected, magnesium (Mg) concentration increased. Coarse dunite application did not significantly affect crop nutrient concentrations, most likely due to its lower weathering rate. In contrast to what was expected, plant Ni and Cr concentrations did not increase with dunite application. Hence, despite high dunite application in our experiment, plants did not accumulate these heavy metals, and only benefited from the released nutrients, albeit dependent on grain size and rainfall frequency

Is the climate change mitigation effect of enhanced silicate weathering governed by biological processes?

International audienceA number of negative emission technologies (NETs) have been proposed to actively remove CO2 from the atmosphere, with enhanced silicate weathering (ESW) as a relatively new NET with considerable climate change mitigation potential. Models calibrated to ESW rates in lab experiments estimate the global potential for inorganic carbon sequestration by ESW at about 0.5–5 Gt CO2 year−1, suggesting ESW could be an important component of the future NETs mix. In real soils, however, weathering rates may differ strongly from lab conditions. Research on natural weathering has shown that biota such as plants, microbes, and macro-invertebrates can strongly affect weathering rates, but biotic effects were excluded from most ESW lab assessments. Moreover, ESW may alter soil organic carbon sequestration and greenhouse gas emissions by influencing physicochemical and biological processes, which holds the potential to perpetuate even larger negative emissions. Here, we argue that it is likely that the climate change mitigation effect of ESW will be governed by biological processes, emphasizing the need to put these processes on the agenda of this emerging research field

Is the climate change mitigation effect of enhanced silicate weathering governed by biological processes?

A number of negative emission technologies (NETs) have been proposed to actively remove CO2 from the atmosphere, with enhanced silicate weathering (ESW) as a relatively new NET with considerable climate change mitigation potential. Models calibrated to ESW rates in lab experiments estimate the global potential for inorganic carbon sequestration by ESW at about 0.5-5 Gt CO2 year−1, suggesting ESW could be an important component of the future NETs mix. In real soils, however, weathering rates may differ strongly from lab conditions. Research on natural weathering has shown that biota such as plants, microbes, and macro-invertebrates can strongly affect weathering rates, but biotic effects were excluded from most ESW lab assessments. Moreover, ESW may alter soil organic carbon sequestration and greenhouse gas emissions by influencing physicochemical and biological processes, which holds the potential to perpetuate even larger negative emissions. Here, we argue that it is likely that the climate change mitigation effect of ESW will be governed by biological processes, emphasizing the need to put these processes on the agenda of this emerging research field

Our natural capital: Research needs and priorities for the future. White Paper

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