Simple formulation of the soil water effect on residue decomposition

Abstract

Soil water content, θ, is a major factor affecting residue decomposition, but simple formulation of this factor is often lacking. We observed that θ significantly (P < 0.001) affected the residue decomposition constant, kd· When θ varied from 0.09gg-1 to 0.23gg-1, kd ranged from 0.009 to 0.013d-1 and from 0.009 to 0.022d-1 for residues with carbon to nitrogen ratio (C/N) > 30 and C/N < 25, respectively. A θ factor was formulated in terms of the field capacity θFC and the air-dry θ d in the form fw = (θ - θd) / (θFC - θd), and this was used to modify the potential kd as θ varied. Coupling fw with a first-order residue decomposition equation resulted in the prediction of the decomposition of four residue types in the greenhouse (R2 = 0.94; relative root mean square error, RRMSE, = 0.06) and in the field (R2 = 0.93; RRMSE = 0.11). © Taylor & Francis Group, LLC.