Short-term effects of crop rotation, residue management, and soil water on carbon mineralization in a tropical cropping system

Abstract

The purpose of this study was to investigate the short-term effects of maize (Zea mays)-fallow rotation, residue management, and soil water on carbon mineralization in a tropical cropping system in Ghana. After 15 months of the trial, maize-legume rotation treatments had significantly (P < 0.001) higher levels of potentially mineralizable carbon, C 0 (μg CO 2-C g-1) than maize-elephant grass (Pennisetum purpureum) rotations. The C 0 for maize-grass rotation treatments was significantly related to the biomass input (r = 0.95; P = 0.05), but that for the maize-legume rotation was not. The soil carbon mineralization rate constant, k (per day), was also significantly related to the rotation treatments (P < 0.001). The k values for maize-grass and maize-legume rotation treatments were 0.025 and 0.036 day-1 respectively. The initial carbon mineralization rate, m 0 (μg CO2-C g-1 day -1), was significantly (P < 0.001) related to the soil water content, θ. The m 0 ranged from 3.88 to 18.67 and from 2.30 to 15.35 μg CO2-C g-1 day-1 for maize-legume and maize-grass rotation treatments, respectively, when the soil water varied from 28% to 95% field capacity (FC). A simple soil water content (θ)-based factor, f w, formulated as: fw = [θ-θd/ θFC-θd], where θ d and θ FC were the air-dry and field capacity soil water content, respectively, adequately described the variation of the m 0 with respect to soil water (R 2 = 0.91; RMSE = 1.6). Such a simple relationship could be useful for SOC modeling under variable soil water conditions. © 2008 Springer Science+Business Media B.V.