Impact of basalt application on soil chemical properties and elemental uptake by paddy rice through enhanced rock weathering

Enhanced Rock Weathering (ERW) is a negative emission technology in which crushed rock powder is applied to cropland to sequestrate carbon by enhancing chemical weathering of silicate minerals. It is a co-benefit approach to promote crop growth by supplying elements (silicon (Si), calcium (Ca), magnesium (Mg), etc.) from weathering rock as well. In this study, we cultivated paddy rice for 99 days in a pot experiment with Gray Lowland soil (pH = 6.19) with six application rates of basalt equivalent to 0, 5, 10, 20, 50, 100 t ha−1. We investigated the change of soil chemical properties and elemental uptake in rice. Then, we calculated the release of Si, Ca, Mg, potassium (K), and sodium (Na) from the basalt, and carbon balance between before planting and after harvest in the whole system including soil and plant. The application of the basalt increased the total amount of soil available Si and exchangeable Mg and Na in the pot as well as the uptake of Si and Na in rice (p < 0.05). There was no significant difference in arsenic, cadmium, chromium, copper, and nickel concentrations in rice grain among the application rates of the basalt. The release of Si, Mg, and Na from the basalt increased corresponding to the application rate of the basalt, suggesting that the applied basalt was weathered during cultivation, though increased carbon sequestration by the basalt weathering was not detected in 99 days of this experiment. We clearly demonstrated that basalt powder got weathered and released Si, Mg, and Na in paddy field condition and additional Si enhanced paddy rice growth.