83-6 Distribution and variation of soil inorganic carbon in native and irrigated soils of a cold semi-arid dryland system along the Snake River Plain, Idaho

Abstract:

Soil inorganic carbon (SIC) plays a critical role in carbon storage, particularly in semi-arid environments where it often constitutes a significant portion of the total soil carbon pool. This study investigates how land use and soil thickness influence SIC accumulation in soils across a semi-arid landscape of the Snake River Plain, near Kimberly, in south-central Idaho. Twenty-two soil profiles were sampled from native and agricultural soils to determine the SIC storage. Our results show that the depth-normalized mean SIC density for one meter is 33.6 ± 4.8 (kg/m³) for native soils and 38.9 ± 5.4 (kg/m³) for irrigated soils. The mean SIC stocks for the entire soil profile is 91.2 ± 12.8 kg/m² for native soils for an average thickness of 2.54 m and 102.2 ± 14.3 kg/m² for irrigated soils that are 2.79 m thick on average. Results reveal a moderate, but statistically significant positive correlation (R² = 0.63) between soil thickness and SIC stocks, suggesting that soil thickness is an important factor influencing SIC storage. As soil thickness increases, the capacity for SIC accumulation also increases. Both extrapolated SIC and soil depth maps produced larger estimates of SIC stocks (kg/m²) and soil depth, respectively, compared to previous studies in our study area. These higher estimates resulted from incorporating measured data points of both soil depth and SIC stocks for reliable depth estimation and SIC quantification/storage. Our results show that SIC stocks in irrigated soils are apparently higher, however, the ANOVA results for three paired native and irrigated soil profiles show broadly similar SIC distributions between land uses, with depth exerting a significant effect, while land use and its interaction with depth were not significant. This suggests that land use has no statistically detectable effect on SIC storage after ~120 years of cultivation.

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-17398

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