Aggregate‐Protected Carbon in No‐tillage and Conventional Tillage Agroecosystems Using Carbon‐14 Labeled Plant Residue

Publisher Website
Google Scholar
Abstract
No‐tillage (NT) management can result in higher soil organic matter (SOM) levels than conventional tillage (CT) practices. The objective was to investigate the underlying mechanisms in which C is protected under NT management, using 14C‐labeled plant residue as a tracer. Samples were collected from the Horseshoe Bend Research area in Athens, GA. Aggregate‐size distribution, total C, and 14C were measured together with different pools of aggregate‐associated C and 14C from 21‐d laboratory incubations of intact and crushed macro and microaggregates. Compared with CT, NT practices resulted in higher total C and 14C in all aggregate‐size classes of the 0‐ to 2.5‐ and 2.5‐ to 5‐cm layers, except for 14C in the 2000‐μm aggregate‐size class under NT than CT. In contrast, more 14C was found in the 53‐ to 250‐μm and 14C pools, microaggregate‐protected and micro within macroaggregate‐protected C and 14C pools were significantly higher for the 0‐ to 2.5‐ and 2.5‐ to 5‐cm layers under NT than CT. Carbon‐14 pools were generally higher in CT than in NT at the 5‐ to 15‐cm depth, while total C did not differ between tillage treatments at this depth. The results indicate that (i) more young C (14C) is accumulated in the subsurface soil of CT than NT, but this C is not stabilized in the long term, and (ii) short‐ and long‐term stabilization of C is higher in the soil surface layers under NT compared with CT. This C stabilization occurs mainly at the microaggregate level.
Funding Information
  • National Science Foundation (DEB 9527957, DEB 9626770, IBN 9987996)