Priming of soil organic carbon decomposition induced by corn compared to soybean crops

S. R. Mazzilli, A. R. Kemanian, O. R. Ernst, R. B. Jackson, and G. Piñeiro

Soil Biology and Biochemistry (August 2014)

DOI: 10.1016/j.soilbio.2014.04.005

Abstract The rate of soil organic carbon (CS) loss via microbial respiration (decomposition rate k, y−1), and the rate of stabilization of vegetation inputs (CV) into CS (humification rate h, y−1) are usually considered independent of CV. However, short-term laboratory studies suggest that the quality and quantity of CV controls k, which is often referred to as a priming effect. We investigated how the chemical composition of different residues, (corn and soybean) controls k and h under field conditions in a no-till ecosystem. Using CV-driven shifts in δ13C, we estimated changes in carbon (C) stocks, k and h of both the labile particulate organic matter fraction (CPOM) and the stabilized mineral associated organic matter fraction (CMAOM). After two years of high C inputs (corn: 4.4 Mg ha−1 y−1 aboveground and C:N = 78; soybean: 3.5 Mg ha−1 y−1, C:N = 17), we found no changes in CPOM and CMAOM stocks in the top 5-cm of soil or in deeper layers. However, CMAOM in corn had higher k (0.06 y−1) and C output fluxes (0.67 Mg ha−1 y−1) than in soybean (0.03 y−1 and 0.32 Mg ha−1 y−1), but similar rates and fluxes in CPOM in the top 5-cm of soil. In addition, while C inputs to CPOM were also similar for both crops, C inputs from CV to CMAOM were higher in corn (0.51 Mg ha−1 y−1) than in soybean (0.19 Mg ha−1 y−1). Overall, corn plots had higher k and C inputs into CMAOM and therefore higher C cycling in this fraction. Our data suggests that the type of crop residue strongly influences C cycling in the topsoil of no-till cropping systems by affecting both the stabilization and the decomposition of soil organic matter.

keywords: Priming effect in field conditions; Soil organic carbon decomposition; Humification rate; Corn; Soybean

cite: BibTeX | EndNote | RIS