Summary
This 12-year field trial in paddy soil demonstrates that substituting mineral nitrogen fertiliser with 100% pig manure increases soil organic carbon by 26%, primarily through enhanced lignin input and microbial necromass accumulation in both particulate and mineral-associated fractions. Manure application selectively promoted r-strategist bacteria with greater capacity for lignin and bacterial necromass production, whilst combined mineral and manure application favoured K-strategist fungi and higher mineral-stabilised carbon proportions. The findings indicate that manure-driven shifts in microbial community composition and metabolic strategies are a key mechanism controlling soil carbon storage and stability in intensively managed paddy systems.
UK applicability
The findings may have limited direct applicability to UK farming systems, which operate under different climatic, soil, and crop rotation conditions than subtropical paddy systems. However, the mechanistic insights on how manure application reshapes microbial communities to enhance soil carbon persistence could inform UK soil health management strategies, particularly in mixed farming systems using livestock manures, though validation under temperate conditions would be required.
Key measures
Soil organic carbon content; particulate organic carbon (POC); mineral-associated organic carbon (MAOC); amino sugars; lignin content; enzyme activities (cellulose- and lignin-degrading); microbial life strategies (r-strategist bacteria vs K-strategist fungi); phospholipid fatty acid (PLFA) ratios; vanillyl acid-to-aldehyde ratios
Outcomes reported
The study measured soil organic carbon (SOC) content and persistence, including particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) fractions, alongside microbial community composition and enzyme activities over a 12-year rice–wheat rotation field trial. Changes in lignin degradation, microbial necromass accumulation, and shifts in bacterial versus fungal microbial life strategies were quantified.
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