Quality green composts add valuable organic matter to agricultural soils and also provide a slow release of nutrients such as nitrogen, phosphate and potassium, together with a wide range of micronutrients.

The BSI PAS 100 compost certification scheme provides a baseline quality standard for compost, ensuring it is consistent, safe and reliable to use. In 2007, the Quality Protocol for Compost (QPC) was launched in England and Wales to provide a clear framework for the production and supply of quality compost. It builds on BSI PAS100 and clarifies which waste materials can be used in quality compost production, reinforcing traceability throughout the production process by ensuring accurate record keeping. QP compliant compost is classed as a product, not a waste, and therefore does not require an exemption for its use on agricultural land.

Application information
Trials have demonstrated that annual compost applications at 50t/ha, or 100t/ha every other year, in conjunction with Nitrogen fertiliser, could increase potato yields by 2 to 3t/ha.

These effects were evidenced after just 2 or 3 years of compost application and further benefits can be expected with the longer term use of compost, particularly on the lighter soil types (this is currently being investigated on two sites).

The trials also demonstrated the long-term benefits of compost applications on soil structure and water retention

When using compost, as with other organic material inputs, you must comply with Nitrate Vulnerable Zone (NVZ) rules where relevant (i.e. the field spreading limit of 250kg/ha total N per year, which equates to around 30t/ha for most green composts, and around 20t/ha for typical food included composts). You should also take account of guidance in the Defra Code of Good Agricultural Practice to Protect Water, Soil and Air Quality (England and Wales).

An exemption from the Waste Management Licensing Regulations is not needed for BSI PAS 100 certified compost if it also complies with the Quality Protocol.

In England and Wales when using compost which complies with the Quality Protocol the farmer/land manager is required to provide certain information to the Environment Agency e.g. where the compost was applied, the rate used, date of application and soil analysis. This data is input via the webtool.

Other considerations
Customer requirements, such as Assured Produce crop protocols, must also be considered. Other guidelines for the use of compost in potatoes are currently being considered.

Animal by-products
Composts containing any animal by-products (e.g. catering wastes) are subject to stringent processing requirements and covered by restrictions on use in accordance with the Animal By-Products Regulations (ABPR); this ensures that they are safe and fit for purpose.