Summary
This 20-year field trial, conducted across four contrasting English sites, demonstrated that repeated biosolids application (3.4 t ha⁻¹ y⁻¹) significantly increased soil organic matter by 10–17%, enhanced available water capacity by up to 10%, and raised key soil nutrients (nitrogen +20%, phosphorus +48%, sulphur +30%) relative to inorganic-fertiliser-only controls. Earthworm populations approximately doubled where low-metal biosolids were applied, with no adverse effects on crop quality observed. These findings support biosolids recycling as a sustainable practice for maintaining long-term soil health and fertility on agricultural land.
UK applicability
This research was conducted on four established experimental sites across England with contrasting soil types and agroclimatic conditions, providing directly applicable evidence to UK agricultural practice and policy. The findings inform United Kingdom biosolids recycling policy and provide a robust evidence base for continued sustainable landbank management of biosolids as a soil amendment.
Key measures
Soil organic matter (% change); light-fraction SOM (mg kg⁻¹); available water capacity (% change); water infiltration rate; aggregate stability; soil total nitrogen (% increase); extractable phosphorus (% increase); total sulphur (% increase); earthworm numbers and biomass; crop quality assessment
Outcomes reported
The study quantified the effects of 20 annual biosolids applications on soil physical, chemical, and biological properties across four contrasting English sites. Key measurements included changes in soil organic matter, nutrient status, available water capacity, water infiltration, aggregate stability, and earthworm populations.
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