Evidence of rapid basalt dissolution in Southeastern US croplands

Enhanced weathering (EW) with crushed silicate rocks has been proposed as a potential form of carbon dioxide removal. This process requires relatively low capital cost, has high global implementation potential, and can provide agronomic and fertility co-benefits to landowners. However, to date, there are limited published, at-scale estimates of empirically constrained weathering rates on working farms. Here, we present estimates of ultrafine basalt enhanced weathering rates from an extended growing season based on over 1,800 samples from 24 fields across Southern Virginia and North Carolina, compared against 24 unapplied fields. This deployment utilizes a paired sample-resample design to constrain between-field heterogeneity, thereby reducing uncertainty. Area-weighted means of three soil mass balance approaches showed that 21.23 ± 7.44% (SEM) of the applied feedstock weathered in approximately six months, with an associated potential carbon dioxide removal of 3.79 ± 1.36 tCO2 ha-1. This value is consistent with weathering rates predicted from a first-order kinetic model driven by feedstock-specific properties.