Soil Organic Carbon Sequestration Rates under Crop Sequence Diversity, Bio-Covers, and No-Tillage
2014
Climate change may be mitigated through soil organic C (SOC) storage under no-tillage; however, crop management influences on SOC are not well defined in all systems. Our objective was to compare long-term C fluxes under two no-tillage sites at Research and Education Centers in Milan (RECM) on Oxyaquic Fragiudalfs and at Middle Tennessee (MTREC) on a Typic Paleudalf in a split-block design with four replications. The whole-block was cropping sequences of corn (Zea mays L.), soybeans [Glycine max (L.) Merr.], and cotton (Gossypium hirsutum L.) with split-block bio-cover treatments of winter wheat (Triticum aestivum L.), hairy vetch [Vicia villosa Roth subsp. villosa], poultry litter, and a fallow control. The same sequences were performed at MTREC without cotton. Soil C flux was calculated at surfaces (0–5 cm) and subsurfaces (5–15 cm) during Year 0, 2, 4, and 8. During the first 2 yr, C losses occurred in all treatments and locations (1.40 and 1.20 Mg ha⁻¹ at RECM and MTREC, respectively), with stabilization initiating by Year 4. By Year 8, sequences with high frequencies of soybean and greater temporal complexity gained more surface SOC. Poultry litter bio-covers gained more surface SOC compared to wheat, vetch, and fallow bio-covers (P < 0.05). After 8 yr, surface SOC surpassed initial levels (9.20 and 8.79 Mg ha⁻¹), with mean gains of 1.33 and 1.16 Mg C ha⁻¹ at RECM and MTREC, respectively. Losses occurred in subsoils at MTREC and RECM, but by Year 8 several treatments had recovered to near baseline levels. Results suggest surface C storage may be enhanced by crop sequence diversity combined with poultry litter bio-covers in no-till systems, whereas subsurface levels may require more time.
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