Enduring increases in maize yield are a co-benefit of enhanced weathering of Greenlandic glacial rock flour in Ghana

Greenlandic glacial rock flour (GRF) is a potential source of extremely fine-grained silicate minerals for CO₂ uptake via enhanced rock weathering. The chemical makeup of this material also indicates that it may be a good source of plant nutrients. GRF was applied at rates of 10 (GRF₁₀) and 50 (GRF₅₀) t ha⁻¹ to a low-fertility sandy clay loam in Ghana to evaluate its impact on maize production relative to a control over five consecutive growing seasons. Other soil amendments, including N fertilizers, were uniformly applied across all treatments. GRF₅₀ significantly increased grain and total dry matter yield (TDMY) across all five seasons. Seasonal increases in TDMY with GRF₅₀ ranged from 28–87% relative to the control, and grain yield increases ranged from 28–77%. In total over the course of the five growing seasons, GRF₅₀ produced an additional 12.9 t ha⁻¹ of TDMY and 7.6 t ha⁻¹ of grain relative to the control. GRF₁₀ had a significant effect on TDMY and grain yield in the first two growing seasons, though the effect of GRF₁₀ decreased over time and by the fifth growing season TDMY and grain yield were equivalent to the control. Nonetheless, the application of this lower amount of GRF still resulted in an additional 7.4 t ha⁻¹ of TDMY and 4.5 t ha⁻¹ of grain yield over the course of the experiment. These results suggest that the significant co-benefits of GRF as a fertilizer may incentivize the adoption of enhanced rock weathering in tropical, nutrient-poor environments and could increase food security in such regions.