Interactive effects of crop residue quality and nitrogen fertilization on soil organic carbon priming in agricultural soils

Abstract

Soil organic carbon (SOC) priming affects C sequestration in soils, the intensity of which differs depending on residue quality. N fertilization could also alter SOC priming. However, the interaction of crop residue quality and N fertilization on the SOC priming is still not clear. To address this gap in knowledge, we conducted this study. We undertook a 110-day laboratory incubation experiment to evaluate the SOC priming and sequestration induced by maize shoot and root residues with and without the application of mineral fertilizer-N in two types of agricultural soils (Andisol and Entisol). Application rates of maize residue and N were 3 g C kg−1 soil and 60 mg N kg−1 soil, respectively. 13C-labeled maize residue allowed quantifying residue decomposition and calculating SOC priming and sequestration. After 110 days of incubation, the cumulative intensity of priming effect was higher for root residue than shoot residue. Addition of N results in contrasting effects on the priming effect induced by root and shoot residue in both types of soils; with root residue, it reduced the intensity of priming effect and resulted in a higher net C sequestration because of reduced N mining, whereas it had little effect with shoot residue, where co-metabolism is the likely explanation for the positive priming effect. Crop residue quality and N fertilization can interactively affect the SOC priming. N fertilization is beneficial for soil C sequestration when soil is treated with low-quality crop residue (e.g., root residue) because of lowering of the intensity of priming effect and crop residue decomposition.