Authors
Noah W. Sokol, Jaeeun Sohng, Kimber Moreland, Eric Slessarev, Heath Goertzen, Radomir Schmidt, Sandipan Samaddar, Iris Holzer, Maya Almaraz, Emily Geoghegan, Benjamin Houlton, Isabel Montañez, Jennifer Pett-Ridge & Kate Scow
23 July 2024
Citations: Sokol, N.W., Sohng, J., Moreland, K. et al. Reduced accrual of mineral-associated organic matter after two years of enhanced rock weathering in cropland soils, though no net losses of soil organic carbon. Biogeochemistry (2024).
https://doi.org/10.1007/s10533-024-01160-0
Abstract
Enhanced rock weathering (ERW), the application of crushed silicate rock to soil, can remove atmospheric carbon dioxide by converting it to (bi) carbonate ions or solid carbonate minerals. However, few studies have empirically evaluated ERW in field settings. A critical question remains as to whether additions of crushed rock might positively or negatively affect soil organic matter (SOM)—Earth’s largest terrestrial organic carbon (C) pool and a massive reservoir of organic nitrogen (N). Here, in three irrigated cropland field trials in California, USA, we investigated the effect of crushed meta-basalt rock additions on different pools of soil organic carbon and nitrogen (i.e., mineral-associated organic matter, MAOM, and particulate organic matter, POM), active microbial biomass, and microbial community composition. After 2 years of crushed rock additions, MAOM stocks were lower in the upper surface soil (0–10 cm) of plots with crushed rock compared to unamended control plots. At the 2 sites where baseline pre-treatment data were available, neither total SOC nor SON decreased over the 2 years of study in plots with crushed rock or unamended control plots. However, the accrual rate of MAOM-C and MAOM-N at 0–10 cm was lower in plots with crushed rock vs. unamended controls. Before ERW is deployed at large scales, our results suggest that field trials should assess the effects of crushed rock on SOM pools, especially over multi-year time scales and in different environmental contexts, to accurately assess changes in net C and understand the mechanisms driving interactions between ERW and SOM cycling.
Mineral-associated organic matter C and N in upper surface soil (0–10 cm) of plots with crushed meta-basalt rock versus unamended control plots across three cropland enhanced rock weathering field trials in California, USA. Stocks of a mineral-associated organic matter C (MAOM-C), and b mineral-associated organic matter N (MAOM-N) at 0–10 cm depth in plots amended with crushed rock (orange bars) relative to control plots (blue bars) in fall 2021. Stocks are expressed as g C (or N) m−2 by thickness of soil layer (i.e., 10 cm). There were 13 replicates (n = 13) per treatment across all field trials. At the sites where baseline data was available (Yolo and Merced-2), we calculated plot-specific changes in the concentration of c MAOM-C (mg C g soil−1) and d MAOM-N (mg N g soil−1) over the two-year period. There were 8 replicates (n = 8) across the two field trials with baseline data. Changes in MAOM-C or N over time were measured by change in concentration (mg C or N g soil−1) in fall 2021 versus pre-treatment baseline values in early fall 2019
Source: Springer Link
