The Organic Research Centre has been conducting research on compost for over 40 years, through a variety of projects, writes Isi Mackintosh.
The current Feed the Soil project builds on this legacy of compost knowledge to develop practical advice developed in real-world conditions in the UK on the best way to compost organic wastes and apply it (or its products) to produce a biologically active product to feed the soil. To address this gap, a comparison of different composting methods and application strategies will be conducted under robust, controlled conditions across a network of farms to generate clear practical guidance for farmers. As part of the Feed the Soil project we will build a knowledge hub to serve as a one-stop-shop for information on ways to manage organic materials and build healthy soils.
In 1993 ORC (then Elm Farm Research Centre), introduced the idea of on-farm composting of household waste to the UK, working with North Wiltshire District council on a pilot scheme.
In 2008 the Institute of Organic Training & Advice (set up with the support of, and later amalgamating with, ORC – see Organic advice and conversion) produced several research topic reviews on compost…
Many organic arable and horticultural systems are stockless, a move away from traditional mixed farming systems allows for the conversion to organic farming without the requirement to introduce livestock and the associated expensive infrastructure costs. However, one of the challenges of a stockless farm is maintaining soil nutrient status without livestock manure. The Management & sustainability of stockless organic arable and horticultural systems research topic review by Keith Preston concluded that the fertility building clover leys and other forage crops grown as green manures are crucial to maintaining fertility in the soil in a stockless system. The review also highlighted that there wasn’t any research evidence for the lack of animals or manure-based compost affecting soil fertility and crop yield however there is evidence that animal manure enhances soil mycorrhizae populations and soil organic matter accumulation.
Another research topic review by Roger Hitchings addressed some of the questions around compost effects on nutrients, soil health and crop quantity and quality. As fresh or stored manure is available to many farmers, the research review addressed whether it is beneficial to use this manure to produce compost. The review stressed that the use of compost has considerable potential for improving soil chemical and physical properties but it shouldn’t be assumed that all composts will deliver the same benefits. The input materials, how the process has been managed and what the objective of the application is will all produce huge variation in the compost and its ability to improve soil condition and crop yield.
A technical leaflet on this research was produced, it gives a good overview of the findings and key information about composting. Compost has also been suggested as a method of controlling pests and diseases in organic field vegetables, a research review by Anton Rosenfeld and Phil Sumption highlights some of the research to support and counter this. Although, disease suppression can often be achieved in pot experiments results in the field seem to be more variable, this was put down to the variation in starting materials, methods of production and testing methods. Compost teas are also discussed in the review, with a wide range of literature showing that compost teas provide some control of diseases.
This work was expanded by Dominic Amos in an Innovative Farmers field lab which investigated compost tea as a microbial inoculant in an organic arable farming system. The field lab investigated the aerobic compost tea making process through soil testing as well as effects on the crop and grain yield. The basic trial design didn’t allow for the effects of the treatment to be significant, however, in one year the spring oats had an improvement in specific weight with the application of compost tea. The soil biology results did show improvements in active fungi from compost tea application. An overview of this field lab was produced for the ORC bulletin in 2016. A practice abstract as part of OK-Net Arable was produced on the topic: aerated compost tea improves soil biology and acts as a biofertiliser/bio fungicide. The practice abstract highlights that the effectiveness of compost tea depends on the quality of the mature compost used in its production. Also, the process of producing compost tea is crucial to its success in improving soil biology and benefiting arable crops.
As part of a Defra Project on Organic Management Techniques two practice abstracts were produced on the topic of compost. Practice Abstract 3 on “Manure and compost as a fertiliser” found that when used effectively as part of a Nutrient Management Plan, manure and compost act as a valuable fertiliser and soil conditioner. Practical recommendations are also included in the practise abstract, one of the issues highlighted is the cost associated with storage as well as access to the input materials to make compost. Practice Abstract 9 on “Use of green waste compost” addresses the issue of availability of compost input materials through the utilisation of landscaping and garden waste which would otherwise go to landfill.
The WOOdchip For Fertile Soils (WOOFS) project investigated the role of woodchips in soil health specifically for increasing soil organic matter, water holding capacity and nutrient levels. The project aimed to identify an alternative to compost, addressing barriers such as the cost and sustainability concerns of sourcing it externally, as well as the lack of time and space for the composting process. The alternative is using woodchip produced on the farm from management of trees and hedges either composted or applied fresh as Ramial Chipped Wood (RCW). Through farm trials different applications of RCW, composted woodchip and green waste compost were applied to an organic vegetable production system, agroforestry alley cropping with organic arable rotation and conventional arable cropping system. Three technical guides were produced to highlight the research findings. The logistics and economics of using RCW was focused on in Technical Guide 1. If making a decision based purely on cost, the findings of the report suggest that a farmer would be unlikely to choose RCW over compost. RCW and compost will also have different actions on the soil despite both adding organic matter, this is further developed in Technical Guide 2 RCW application had varied effects across different farming systems, with potential benefits such as improved crop resilience, reduced pest damage, and increased phosphorus availability. Trials also suggest that woodchip and compost enhance soil water retention, helping crops cope with extreme weather conditions. A recommendation from this technical guide was that compost and RCW should be mixed together or the application alternate as they both have different actions on the soil. Technical guide 3 reports that RCW produced on farm currently has less regulatory requirements than green waste compost, but there are other restrictions that need to be considered to produce RCW such as timing of hedge coppicing and felling licenses. Iain Tolhurst, one of the WOOFS operational group members, spoke about woodchip compost to manage soil fertility on his organic vegetable farm.
Building on this foundation of past ORC composting research, reports and learnings Feed the Soil was launched in 2024 in collaboration with The Land Gardeners and a wide range of farmers across the UK who are developing innovative ways to manage organic wastes and produce amendments to promote healthy soils and soil life. Methods include biodynamic or controlled microbial composting, passive aeration like Johnson-Su, anaerobic fermentation including bokashi, and systems that use worms (vermicomposting). Many farmers are producing extracts and teas to treat soils and their crops too. A detailed review of the academic literature was conducted over the summer to identify gaps in knowledge about the many approaches to composting organic materials and use their products. A survey of methods is now underway with visits to practitioners to document their approaches and challenges. This preliminary work will be used to frame research questions and design on-farm trials during 2025. In parallel with the research activities, we will be developing resources that highlight success stories and provide examples of resource-efficient ways practitioners are recycling organic wastes, improving nutrient cycles on farms and promoting healthy soil biological communities that support healthy crops and people.
