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Applying biochar to agricultural soils has been proposed as a means of sequestering C while simultaneously enhancing soil health and agricultural sustainability. However, our understanding of the long-term effects of biochar and annual versus perennial cropping systems and their interactions on soil properties under field conditions is limited. We quantified changes in soil C concentration and stocks and other soil properties 6 yr after biochar applications to corn (Zea mays L.) and dedicated bioenergy crops on a Midwestern US soil. Treatments were: no-till continuous corn, Liberty switchgrass (Panicum virgatum L.), and low diversity prairie grasses, 45% big bluestem (Andropogon gerardii), 45% Indiangrass (Sorghastrum nutans) and 10% sideoats grama (Bouteloua curtipendula), as main plots, and wood biochar (9.3 Mg ha-1 with 63% total C) and no biochar applications as subplots. Biochar-amended plots accumulated more C (14.07 vs. 2.25 Mg soil C ha-1) than nonbiochar amended plots in the 0 to 30 cm soil depth but other soil properties were not significantly affected by the biochar amendments. The total increase in C stocks in the biochar-amended plots was nearly twice (14.07 Mg soil C ha-1) the amount of C added with biochar 6 yr earlier (7.25 Mg biochar C ha-1), suggesting a negative priming effect of biochar on formation and/or mineralization of native soil organic C. Dedicated bioenergy crops increased soil C concentration by 79% and improved both aggregation and available water in the 0 to 5 cm soil depth. Biochar did not interact with the cropping systems. Overall, biochar has potential to increase soil C stocks both directly and through negative priming, but in this study had limited effects on other soil properties after 6 yr.
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Blanco-Canqui, Humberto; Laird, David; Heaton, Emily; Rathke, Sam; and Sharma Acharya, Bharat, "Soil carbon increased by twice the amount of biochar carbon applied after six years: Field evidence of negative priming" (2019). Agronomy Publications. 617.