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Assessment of Labile Organic Carbon in Soil Using Sequential Fumigation Incubation Procedures
Published on: October 29, 2016
Microbial versus plant carbon partitioning governs organic carbon formation pathways in paddy and upland soils under
Jia Zeng1, Jiale He1, Yirui He1
1College of Agronomy, Northwest Agriculture & Forestry University, Yangling, 712100, Shaanxi, PR China; Shaanxi Engineering Research Center of Circular Agriculture, Yangling, 712100, Shaanxi, PR China.
Abstract:
Global cropland soils possess significant carbon storage potential, yet their storage efficiency is directly regulated by fertilization practices. To elucidate the impact of fertilization on soil organic carbon (SOC) in major cropland systems (paddy/upland), this study leverages a 37-year long-term field experiment. We integrate physical fractionation (particulate organic carbon (POC), mineral-associated organic carbon (MAOC)) and biomarker techniques (plant-derived carbon, microbial necromass carbon) to systematically analyze carbon pool reconfiguration pathways under four fertilization treatments: no fertilizer (CK), nitrogen-only fertilizer (N), NPK fertilizers (NPK), and combined organic-inorganic fertilization (NPKM). Key findings are as follows: NPKM significantly increased SOC by 52.6% in upland and 29.4% in paddy. In contrast, chemical-only fertilization (N/NPK) achieved no increase in carbon storage, confirming the essential role of organic carbon inputs in cropland carbon storage. In paddy soils, flooded conditions suppressed microbial decomposition and saturated the MAOC pool, leading NPKM treatment to drive preferential carbon enrichment into the POC fraction. Conversely, NPKM treatment in upland soils concurrently enhanced both POC and MAOC pools, demonstrating a synergistic dual-pool accumulation mode. NPKM induced substantial increases in plant-derived carbon (lignin phenol biomarkers) in upland (458.9%) and paddy soils (188.1%). This contributed 63.5% and 65.7% of SOC under NPKM in upland and paddy soils, respectively, highlighting its dominant contribution to SOC accumulation. NPKM treatment also increased microbial necromass carbon but shifted its composition toward fungal necromass dominance in upland soils and bacterial necromass dominance in paddy soils. In conclusion, NPKM exhibits prominent carbon storage potential in both upland and paddy systems. However, distinct carbon storage patterns emerge due to differences in water management. This necessitates targeted carbon storage strategies specifically designed for the distinctive characteristics of paddy and upland systems.
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