Increased yield and CO₂ sequestration potential with the C₄ cereal Sorghum bicolor cultivated in basaltic rock dust‐amended agricultural soil

Abstract

Land-based enhanced rock weathering (ERW) is a biogeochemical carbon dioxide removal (CDR) strategy aiming to accelerate natural geological processes of carbon sequestration through application of crushed silicate rocks, such as basalt, to croplands and forested landscapes. However, the efficacy of the approach when undertaken with basalt, and its potential co-benefits for agriculture, require experimental and field evaluation. Here we report that amending a UK clay-loam agricultural soil with a high loading (10 kg/m 2 ) of relatively coarse-grained crushed basalt significantly increased the yield (21 ± 9.4%, SE) of the important C 4 cereal Sorghum bicolor under controlled environmental conditions, without accumulation of potentially toxic trace elements in the seeds. Yield increases resulted from the basalt treatment after 120 days without P-and K-fertilizer addition. Shoot silicon concentrations also increased significantly (26 ± 5.4%, SE), with potential benefits for crop resistance to biotic and abiotic stress.Elemental budgets indicate substantial release of base cations important for inorganic carbon removal and their accumulation mainly in the soil exchangeable pools.Geochemical reactive transport modelling, constrained by elemental budgets, indicated CO 2 sequestration rates of 2-4 t CO 2 /ha, 1-5 years after a single application of basaltic rock dust, including via newly formed soil carbonate minerals whose longterm fate requires assessment through field trials. This represents an approximately fourfold increase in carbon capture compared to control plant-soil systems without basalt. Our results build support for ERW deployment as a CDR technique compatible with spreading basalt powder on acidic loamy soils common across millions of hectares of western European and North American agriculture. K E Y W O R D Scarbon removal, crop productivity, mineral weathering, negative emissions technology, reactive transport modelling, silicon, soil acidification KELLAND Et AL. | 3659

Optimizing Inorganic Carbon Sequestration and Crop Yield With Wollastonite Soil Amendment in a Microplot Study

“…In this microplot study, the plots were open to drainage to emulate the setup as close as possible to the field conditions. Based on the detailed study provided by Kelland et al. (2020) , elemental mass budgets indicate that the products of basalt dissolution (alkalinity and cations) do not immediately transport directly to the marine environment via surface waters because of uptake of elements into plant biomass and temporary sequestration onto soil exchangeable sites (e.g.…”

“…'s data, who reported on a plot composed of compost and quarry fines, and showed the net rate of accumulation to be in the order of 0.15 kg CO 2 ·m −2 ·month −1 to a depth of 3 m ( Manning et al., 2013 ). Kelland et al. (2020) report soil inorganic carbonate precipitation via basalt weathering in soil used to grow sorghum, reporting 0.24 kg CO 2 ·m −2 ·year −1 (0.02 kg CO 2 ·m −2 ·month −1 ) sequestration using basalt application.…”

“…The highest calcium carbonate accumulation of 3.22 g•kg −1 reported in this study, obtained over 14 weeks, is equivalent to net monthly accumulation of 0.08 kg CO 2 •m −2 •month −1 , for a soil depth of 0.15 m. This value compares favorably to Manning et al's data, who reported on a plot composed of compost and quarry fines, and showed the net rate of accumulation to be in the order of 0.15 kg CO 2 •m −2 •month −1 to a depth of 3 m . Kelland et al (2020) report soil inorganic carbonate precipitation via basalt weathering in soil used to grow sorghum, reporting 0.24 kg CO 2 •m −2 •year −1 (0.02 kg CO 2 •m −2 •month −1 ) sequestration using basalt application. It is of the same order of magnitude as the rate reported in this study (0.08 kg CO 2 •m −2 •month −1 ).…”

Possibilities and Prospects Regarding Ethanol Production from Saccharin Sorghum [Sorghum bicolor (L.) Moench]

“…Grossi et al [70], in their study on the vulnerability of sorghum production for the current (1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999) and future (2047-2064) seasons, applying climatic observations and climatic results, concluded that with regard to future conditions , the simulations indicated that in Janaúba (Brazil) the average yields for current and future climatic conditions were not statistically different, but in Sete Lagoas (Brazil) there was a statistically significant increase in sorghum productivity. Kelland et al [71], in their study on improved soil-based rock weathering (ERW) concluded that reactive geochemical transport modeling, limited by elementary budgets, indicated CO 2 sequestration rates of 2-4 t CO 2 /ha, 1-5 years after a single application of basaltic rock powder, it is known, however, that elementary budgets indicate substantial release of basic cations important for the removal of inorganic carbon and its accumulation mainly in exchangeable soil reservoirs.…”

Enhancing Natural Cycles in Agro-Ecosystems to Boost Plant Carbon Capture and Soil Storage

“…Actual basalt weathering rates and hence carbon drawdown potential remain uncertain, depending strongly on particle size (limited by grinding cost), climatic and soil conditions, and biological activity 8,47,48 . Water flow is critical because mineral surfaces have to be in contact with water for the dissolution reaction to take place, and disturbed for the reaction to continue 49 .…”