Plastic film mulching and nitrogen fertilization enhance the conversion of newly-added maize straw to water-soluble organic carbon

Abstract

Water-soluble organic carbon (WSOC) represents a small but dynamic fraction of soil organic carbon (SOC) and plays a key role in the terrestrial carbon cycle. Some researchers have indicated that the WSOC has been affected by soil tillage. However, there is still a gap in knowledge regarding WSOC dynamics within agricultural practices in many regions, including northeast China. This study assesses the influence of a common management practices, namely plastic film mulching (PFM) and fertilization treatments (nitrogen and manure), on the dynamics of WSOC and straw-derived WSOC (WSOCstraw) in continuous maize (Zea mays L.) topsoil (0−20 cm) over a 360-day period. In this study, an in situ13C-tracing technique using pulse-labeled maize straw within bulk soil and soil aggregates (>2 mm, 1−2 mm, 0.25−1 mm and < 0.25 mm by dry sieve method) found that PFM coupled with nitrogen (N, urea) fertilization increased the final contents of WSOC (250 mg kg−1 soil) and WSOCstraw (30 mg kg−1 soil) within bulk soil. In addition, the overall content of WSOCstraw exhibited an inverse relationship to the content of straw-derived microbial biomass carbon. These dynamic changes in WSOC are likely due to enhanced nutrient-controlled microbial decomposition and uptake of maize straw-derived carbon. Soil aggregates did not show consistent changes as observed in the bulk soil. Our findings provide important insights into WSOC dynamics under PFM application and fertilization practices.