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Abstract Cultivation, high temperatures, and a semiarid climate accelerate organic carbon (OC) loss and weaken soil structure in the Southern Plains. Our hypothesis was that differences in soil C storage attributable to tillage method are related to differences in soil respiration and microbial biomass dynamics. Carbon dioxide fluxes following wheat ( Triticum aestivum L.) harvest were determined in Bethany silt loam (fine, mixed, thermic Pachic Paleustoll). Treatments were moldboard plowing (MP) and no‐till (NT) at two residue rates (0 and 4 Mg ha −1 ). Soil respiration was measured from 1 August to 30 September using closed chambers. Peak CO 2 ‐C flux densities reached 1.3 g m −1 d −1 in NT for 2 d and stabilized at 0.4 g m −1 d −1 . The CO 2 ‐C evolution peaked at 4.1 and 2.9 g m −1 d −1 in MP with and without buried residues, respectively. After 3 d, they decreased to a steady state of 0.4 g m −1 d −1 . Daily average temperatures in the 0‐ to 0.2‐m depth were 0.5 to 3.4°C higher under MP than NT, increasing microbial adenosine triphosphate (ATP), biomass C, and CO 2 ‐C fluxes. The proportion of soil OC respired in the 60‐d period was twice as great under MP than NT, accounting for 0.42 to 0.58% and 0.19 to 0.22%, respectively. After 11 yr, NT soil OC showed increases of 65, 17, and 7% over the MP for the 0‐ to 0.05‐m, 0.05‐ to 0.1‐m, and 0.1‐ to 0.2‐m depths, respectively. Tillage and residue incorporation enhanced C mineralization and atmospheric fluxes, suggesting that tillage intensity should be decreased to reduce C loss.
Thanh H. Dao (Thu,) studied this question.