Residue Carbon Stabilization in Soil Aggregates of No-Till and Tillage Management of Dryland Cropping Systems


Tillage events have an important influence on residue incorporation into soil profiles and soil aggregate disruption, and ultimately influence the net C gain or loss in soils. Thus, our objective was to evaluate tillage-induced influences on aggregate structure, residue-derived C stabilization, and the subsequent efficiency of C stabilization in aggregates of no-till (NT) and tillage management (TM) practices at different depth increments of the soil profile. Uniformly 13C-labeled wheat residues were added to incubation cores representing soils under NT and TM during a year-long in situ incubation at a dryland agriculture experiment site. Residue was added directly onto the surface of NT cores, while residues were incorporated into the 0- to 5-, 5- to 15-, and 15- to 30-cm depth increments of the TM cores. We found that residue additions did not have a significant effect (P > 0.05) on aggregate dynamics in either NT or TM, but NT management did result in the greatest stabilization of residue-derived C (11.2 ± 2.4 g residue C kg−1 soil kg−1 residue C added, P < 0.05) in the macroaggregate (>250-μm) fraction of the 0- to 15-cm increment. Residue-derived C stabilization was significantly greater (P < 0.05) in the 0- to 30-cm increment than in the 0- to 15-cm increment of the TM management cores. Overall, our results indicate that, within a plow depth of 15 cm, limiting the tillage-induced disruption of aggregates has a stronger influence on the efficiency of C stabilization than residue incorporation into the profile via tillage. When residues are distributed to a 30-cm depth, however, the negative impact of aggregate disruption through tillage appears counterbalanced, with similar efficiencies of C stabilization between the NT and TM practices, possibly due to slower decomposition of residues deeper in the profile.


Soil Biogeochemistry and Microbial Ecology

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Soil Science Society of America Journal



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