WHAT THE EVIDENCE SAYS
A new review synthesizes field-based evidence on repeated manure application. It finds generally higher soil organic matter, aggregation, microbial biomass and enzyme activity, but also cumulative risks including phosphorus accumulation, nitrate leaching, greenhouse-gas emissions, heavy-metal buildup and antibiotic-resistance genes. The authors emphasize saturation, legacy effects and the interaction of rate, timing, soil texture and application method.
WHY IT MATTERS / OUR READ
Organic nutrient sources are not automatically low-risk. The management problem is a balance sheet: soil structure and fertility can improve while long-lived nutrient or contaminant liabilities accumulate outside the timeframe of a short yield trial.
CAVEATS / UNCERTAINTY
This is a narrative review rather than a quantitative meta-analysis, and the underlying studies vary greatly by manure type, loading rate, soil, climate and duration. The review supports context-specific risk management, not a universal threshold or a conclusion that manure is inherently preferable or harmful.
SOURCE
Water, Air, & Soil Pollution — review
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