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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #413352
Research Project: Development of Management Strategies for Livestock Grazing, Disturbance and Climate Variation for the Northern Plains

Location: Livestock and Range Research Laboratory

Title: Carbon sequestration uncertainty: is grazing-induced soil organic carbon accrual offset by inorganic carbon loss?

Author
item Reinhart, Kurt
item Rinella, Matthew - Matt
item Waterman, Richard
item SANNI WOROGO, HILAIRE - University Of Parakou
item Vermeire, Lance

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2024
Publication Date: 8/7/2024
Citation: Reinhart, K.O., Rinella, M.J., Waterman, R.C., Sanni Worogo, H.S., Vermeire, L.T. 2024. Carbon sequestration uncertainty: is grazing-induced soil organic carbon accrual offset by inorganic carbon loss?. Soil & Tillage Research. 46(2). Article RJ24006. https://doi.org/10.1071/RJ24006.
DOI: https://doi.org/10.1071/RJ24006

Interpretive Summary: Problem- The practice of carbon ranching generally focuses on increasing soil organic carbon. However, drylands often have calcareous soils (i.e. subsoils containing carbonates) and a large portion of their soil carbon is inorganic (e.g. calcium carbonate). We have a poor understanding of whether gains in soil organic carbon may be offset by reductions in inorganic carbon. Accomplishment- Results indicate some grazing treatments increased soil organic carbon accrual but grazing treatments had no effect on soil inorganic carbon stocks at least in the short term. However, we observed a negative relationship between soil organic and inorganic carbon stocks suggesting that the two fractions of soil carbon are often inversely related.

Technical Abstract: Some grassland managers now seek to increase soil organic carbon (SOC) stocks to help decarbonize the atmosphere. In drylands, soil inorganic carbon (SIC) represents the largest fraction of the total soil carbon stock. Little is known about how grazing management affects SIC stocks and whether carbon ranching’s aim of increasing SOC may also reduce SIC (or instead increase SIC). To help fill this gap, we used data from a 5-yr grazing experiment to test whether grazing management treatments impact SIC and whether grazing-induced SOC accrual was offset by depletion of SIC in the Northern Great Plains. The experiment had a randomized complete block design and with pre-treatment data. Response variables were SOC and SIC stocks. Moderate summer grazing (control) is regionally common and treatments that may alter soil stocks included: no grazing, severe summer grazing, moderate fall grazing, and severe fall grazing. We also tested for a trade-off between SOC and SIC across all soil cores (n= 244). Severe grazing (fall and summer) increased SOC relative to moderate summer grazing. However, no treatments affected SIC. Conversely, we found an overall weak but significant near 1-to-1 negative relationship between SIC and SOC stocks of soil cores. Our findings suggest that severe grazing can increase SOC without affecting SIC, at least over the short-term (5-yr). This finding mirrors results from an observational study elsewhere in the Northern Great Plains. However, in the Central Great Plains, a longer, un-replicated study suggests moderate and severe grazing can increase SIC compared to no grazing. Therefore, there is some chance our grazing treatments would affect SIC if continued for longer periods.