Meeting P Demand in European organic farms: Is it time to change the Standard?

Summary

Organic farming standards regulate allowable nutrient inputs according to the core principles of: reliance on renewable resources, recycling of wastes and by-products of plant and animal origin, and feeding of plants through the soil ecosystem and not through soluble fertilizers, balanced against a goal to produce high quality products with a minimum level of contaminants. These criteria are applied to the list of currently permitted inputs in organic agriculture, known as "Annex 1" of the European Commission Regulation EC No. 889/2008. This list currently excludes some potentially useful sources of societal waste (e.g. some sources of household waste and digestate, sewage sludge), but allows other sources which may pose higher risks according to some criteria (e.g. conventional manure sources, mined rock P).
The IMPROVE-P project (CORE Organic II) sought to address the issue of P in organic farming through gathering evidence about systems that may be deficient in P, investigating alternative P fertilizers (APFs) for use in organic farming systems, and collecting information on farmer and stakeholder attitudes to APFs in organic farming.
Compilation and analysis of soil test data from organic farms in several European countries indicated that organically managed soils are generally at the low end of the spectrum for P availability. This is particularly evident in German arable farms, Austrian dairy farms, and Swiss mixed farms. This suggests that more recycling of P back to organic land needs to take place.
The project produced several factsheets exploring the risks and benefits of using some currently banned APFs (improve-p.uni-hohenheim.de). The factsheet on sewage sludge precipitation products highlighted advances in wastewater treatment that produces APFs which can have lower concentrations of potentially toxic elements than some rock P, conventional animal manures, or bio-waste composts. Workshops with farmers and stakeholders in several European countries indicated regional differences in attitudes towards APFs. In the UK 70% of respondents considered sewage sludge products (e.g. biosolids) an acceptable APF for organic farmers, in contrast to only 15% of respondents in Norway. P precipitates were considered an acceptable APF by 70% of all respondents.
The project has highlighted the need to revisit the current list of permitted inputs and demonstrated the potential to introduce new APFs into organic farming to address the long-term deficit of P on many organic farms.