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24th March 2022

Moving to more sustainable methods of slurry application: implications for water quality of waterbodies and water protected areas

CRW2020_02_Front_Cover Cover photographs courtesy of: NFUS, Stock Adobe

This report is a quick scoping review (QSR) of peer reviewed and grey literature to provide an evidence-based comparison of different low emission slurry spreading (LESS) approaches in terms of farming practice, ammonia and nitrous oxide emissions and risk of water pollution from slurry spreading to inform farmer-focused guidance on LESS. The work is focused on slurry-borne contaminants that are relevant to the water quality objectives under the river basin management plans (RBMP) set by the Scottish Environment Protection Agency (SEPA), such as nitrate, phosphorus and faecal indicator organisms (FIO).

The key question addressed by the project is ‘What are the effects of low emission slurry spreading (LESS) approaches on water quality?

This QSR showed that the key factors influencing the impact of LESS approaches on losses of slurry-borne pollutants to water are precipitation, soil moisture, soil permeability and drainage, and presence of vegetation, be it crop, grass or vegetated buffer strips. The role of these factors has already been captured in the current regulatory framework, stipulating specific obligations for farmers under GBR18 and The Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2008. The already existing guidance is still valid to protect water quality.  However, the choice of LESS approach should be determined by environmental designations and account for the most vulnerable environmental component (soil/atmosphere/ waterbodies) of the agro-ecosystem. Guidance to farmers should also consider a compromise between feasibility, cost, and environmental and agronomic objectives.