Changes in soil organic carbon stocks from reducing irrigation can be offset by applying organic fertilizer in the North China Plain

Abstract

Elaborate water and fertilization management to increase soil organic carbon (SOC) accumulation is important in maintaining high agricultural productivity and a sound ecological environment. Here, a field experiment was conducted for eight years to investigate the effects of irrigation regimes and fertilizer types on SOC stocks and labile organic carbon concentrations (particulate organic carbon, POC; dissolved organic carbon, DOC; and microbial biomass carbon, MBC). The irrigation regimes were no irrigation (W0); presowing irrigation (W1); presowing and jointing irrigation (W2); and presowing, jointing, and anthesis irrigation (W3). The fertilizer types were no fertilizer (C0), mineral fertilizer only (C1), half mineral plus half cattle manure (C2), and cattle manure only (C3). Thus, sixteen treatments were created and laid out in a split block design with triplicates. Both irrigation and manure application distinctly enhanced SOC accumulation. POC, DOC, and MBC were mainly affected by manure application in surface soil (0–20 cm) and by irrigation in deep soil (40–60 cm). The interaction between irrigation and fertilization on SOC and labile organic carbon concentrations was not significant in the 0–60 cm soil layer. The SOC stocks and relative SOC sequestration rate increased with increasing irrigation and cattle manure inputs. There was no significant difference in SOC stocks between W2C2 (108.15 Mg C ha−1) and W3C1 (109.05 Mg C ha−1), as well as between W1C2 (90.25 Mg C ha−1) and W2C1 (87.07 Mg C ha−1), indicating that in W2 and W1, replacing half of the nitrogen with organic manure can result in equal SOC stocks caused by increasing irrigation under mineral fertilizer alone. This study emphasizes the important role that irrigation plays in SOC management and provides theoretical support to improve the SOC stock by reducing irrigation and applying cattle manure in the North China Plain.