The increasing supply and availability of accredited composted waste material to UK agriculture is likely to have significant benefits to the industry, some of which are noted below.
- The profile and image of UK farming, as viewed by the public and government, will be lifted and improved by agriculture demonstrating its responsibility in helping the government to achieve its waste composting targets under the EU Waste Directive, by utilising composted products as part of an integrated farming system.
- Farmers are able to utilise compost produced by accredited suppliers, working to the BSI PAS 100 code of practice. One of the benefits to the farmer of the compliance by producers to the PAS100 accreditation means that the compost has been sampled to ensure that it complies with quality requirement standards with regard to pathogens, toxic elements and weed and physical contaminants.
- Farmers can confidently use the compost knowing they can easily comply with the guidelines for such materials, as laid down in the various Codes of Good Agricultural Practice, e.g. Soil and Water, RB 209 Fertiliser Recommendations, NVZ guidelines and the objectives for Cross Compliance Guidance for Soil Management within the Single Payment Scheme.
- Farmers can visit www.wrap.org.uk to access various publications relating to the use of compost in agriculture, including reports from farmers and organic growers. The wrap "Organics" Stakeholder Update pages and publications list give a comprehensive explanation and much information relative to the waste recycling of materials.
- Analysis of compost samples will demonstrate to potential users typical nutrient values, enabling them to assess the suitability of the material for their own soil nutrient requirements in the relation to their planned cropping programme and nutrient off-take.
- Typical analysis of composted wood and green waste show significant levels of N, P, and K which, when applied to soils within the levels and conditions laid down in the codes and guidelines mentioned above, provides levels of nutrient which will reduce reliance on artificial fertilisers.
- Typical samples are pH neutral, which may help reduce the need for liming on some soils.
- Use of compost, or other manures, as laid down in the Cross Compliance Guidance for Soil Management "Principles of Good Soil Husbandry", will increase soil organic matter where needed, improve soil stability and increase workability.
- The compost can be regarded as a replacement for Farm Yard Manure for those farmers who need a source of organic material to improve their soils and do not have access to supplies of F.Y.M.
- There will be continuity of supply of accredited product to those farmers using the compost, due to the availability of large volumes of wood and green waste material from local authorities working to comply with the government and EU waste directives.
- Farmers using the compost are most likely to have it supplied on a convenient "delivered, stockpiled and spread" agreement – therefore eliminating the need for investing in their own spreaders and other machinery.
- Farmers are likely to see significant cost saving from a reduction of artificial fertiliser use in crop production where compost is utilised effectively and efficiently in conjunction with good soil management, which will include regular soil sampling to ascertain nutrient levels and crop nutrient requirements.
Quality compost proves its worth for agricultural industry
Scientific trials have shown that using quality compost can bring significant commercial and environmental benefits to a wide range of agricultural crops. For example, compost can improve soil structure and fertility, and reduce the need for non-organic fertilisers.
The main benefit of compost is that it helps to maintain and even increase organic matter levels in soils. With 17 per cent of land in England and Wales showing signs of erosion in 2004 (Defra, 2004), compost can certainly play its role in soil organic matter (SOM) management.
Compost applied at 30 tonnes per hectare (the maximum allowed in Nitrate Vulnerable Zones) provides around 6 tonnes of organic matter, which is more than would normally be supplied by materials such as cattle and pig farmyard manure or sewage sludge cake. More importantly, the organic matter in compost has a long lasting effect, due to its high lignin content that is gradually degraded by soil microbes. SOM is Defra’s highline soil quality indicator and maintaining it is a cross compliance requirement. Organic matter is known to improve the soil structure and to have an effect on its structural stability, its water holding capacity and workability.
Another key benefit of compost is its fertiliser replacement value. In terms of nutrients, it varies according to feedstock, but one tonne of compost typically provides 8 kg Nitrogen, 6 kg Potash and 3 kg Phosphate. According to guidance produced by ADAS – ‘Making the most of Compost in Agriculture and Field Horticulture’ – the typical NPK replacement value from 30 t/ha of compost in the first year is at least £190/ha (based on prices in February 2008). Compost can be used successfully as part of a fertiliser management plan, provided soil type, crop requirements and nutrient release patterns are taken into account.
For example, the rate at which nitrogen is released from compost can vary depending on soil and climate conditions. Typically, Nitrogen in compost is released slowly, therefore reducing the possibility of it leaching away. Between 5 and 10 per cent of the total Nitrogen provided by compost is made available to crops in the first year of application, and more in year two (from the same application). Compost also provides useful amounts of Sulphur and Magnesium, and has a small liming effect.
WRAP is sponsoring a number of scientific trials to assess the impact of compost on crops. This includes a project which was started on Park Farm in East Anglia more than six years ago by Enviros Consulting Ltd. Now managed by Westrope Farming, the trials initially involved two quarter hectare sites, growing sugar beet and potatoes, and was followed by expansion into five more sites in 2002 and the introduction of different crops such as barley, wheat and carrots.
Each trial involved eight different treatments to compare the benefits of applying compost. Two trials with compost applied respectively at 30 t/ha and 60 t/ha biennially were compared with an untreated, control trial, a trial using traditional NPK fertiliser, and trials of compost in conjunction with both standard and reduced levels of Nitrogen. All treatments were replicated four times to ensure that conclusions were based on statistically significant data.
The trials concluded that compost used in conjunction with reduced levels of Nitrogen was as effective as compost with standard levels of Nitrogen, and both were more effective than NPK fertiliser alone.
The key result from the six year project was an average increase of seven per cent in crop yields – for example, the potato crop, growing at 50 t/ha, increased to 53.5 t/ha over the period of the trial. This increase has been attributed to improvements in the soil structure caused by the repeat application of compost. For more information visit www.compost.me.uk/Consolidated_report_phase_2.pdf.
Phil Wallace, Technical Director at Enviros Consulting, said: “Because of the long-term change in the soil structure, there has been a marked improvement in both water infiltration and retention rates, and far less need to apply Phosphate, Potash or Nitrogen fertilisers. The compost is helping the soil hold moisture and nutrients for longer periods which means a healthier bed for crops all year round.”
He continued: “These trials are a landmark for both farmers and the composting industry. They prove the commercial added value that compost can provide, both reducing fertiliser costs and increasing yield, while also providing a range of environmental benefits”.
The success of the trials so far has led to a continuation of field-scale trials on Westrope Farms. In 2006/7, more than 3,000 tonnes of compost was applied to fields before onions were grown. Not only were the compost-grown onions ready to harvest earlier than those grown using conventional fertilisers last summer, the crop yield was 27 per cent greater. The compost used within the trials was produced by BSI PAS 100 certified producers, Country Mulch Ltd and Viridor.
Other arable trials across the country have backed up the results from the Enviros trials and reported further benefits. Independent consultancy Organic Resource Agency (ORA) started work on the Greenleaf Project in 2001. Administered by the Environmental Projects Agency, the scheme provided a selection of farmers with compost every year to assess the effect of its application on soil. The objective was to investigate compost use as a means of improving the productivity of farmland as part of a programme of sustainable land management.
Ten fields on four different farms were treated with different applications of compost to grow sugar beet, winter barley, potatoes, winter wheat and beetroots. The farms were chosen because of their different soil types and each field chosen had the following treatments – 25 t/ha, 50 t/ha, 75 t/ha – plus one specified control plot to clearly compare the benefits of compost application.
Similar to the Park Farm trial run by Enviros, the levels of organic matter in the soil were tested annually and these trials also showed that levels of organic matter rose in seven out of the 10 fields. This led to a rapid increase in workability for farmers, particularly on heavy soils.
The trials also tested the levels of macro nutrients such as Potassium, Phosphorus, Magnesium and Sulphur. There was a clear and steady increase in both Potassium and Phosphorus in the soils, relative to the controls, resulting from the compost application.
The release of Phosphorus was slower than that of Potassium and the trials showed that the Phosphorus in compost could provide long-term benefits. Levels of both Magnesium and Sulphur in the soils tested were also aided by the compost application.
The commercial value of the nutrient increased resulting from repeated compost use was assessed and it was found that farmers could make significant savings by using compost in conjunction with traditional fertilisers. ORA concluded that farmers could be saving more than £55 per hectare per year by complementing traditional fertilisers with compost. This figure may vary a lot according to compost haulage costs and fertiliser prices.
The production supply and use of compost in agriculture is underpinned by a quality assurance scheme – BSI PAS 100 – which has been further enhanced by the introduction last year of the Quality Protocol for Compost.
Agriculture is already the biggest market for compost. As both the commercial and environmental benefits of this sustainable, locally sourced product continue to be realised, its use is likely to continue to increase across all kinds of crops. The compost market also offers business opportunities to farmers who have buildings and land that can be converted into compost production facilities. The Composing Association (TCA) estimates that on-farm sites represent 29 per cent of composting sites across the UK. In fact, according to TCA, the amount of organic waste treated in on-farm facilities in the UK has risen by 35 per cent from 2003/4 to 2004/5.
Compost can turn agricultural soils into a carbon sink, thus protecting against climate change
Applying organic fertilizers, such as those resulting from composting, to agricultural land could increase the amount of carbon stored in these soils and contribute significantly to the reduction of greenhouse gas emissions, according to new research. Carbon sequestration in soil has been recognized by the Intergovernmental Panel on Climate Change and the European Commission as one of the possible measures through which greenhouse gas emissions can be mitigated.
ScienceDaily reports that one estimate of the potential value of this approach -- which assumed that 20% of the surface of agricultural land in the EU could be used as a sink for carbon -- suggested it could constitute about 8.6% of the total EU emission-reduction objective.
"An increase of just 0.15% in organic carbon in arable soils in a country like Italy would effectively imply the sequestration of the same amount of carbon within soil that is currently released into the atmosphere in a period of one year through the use of fossil fuels," write Enzo Favoino and Dominic Hogg, authors of the paper.
"Furthermore, increasing organic matter in soils may cause other greenhouse gas-saving effects, such as improved workability of soils, better water retention, less production and use of mineral fertilizers and pesticides, and reduced release of nitrous oxide."
However, capitalizing on this potential climate-change mitigation measure is not a simple task. The issue is complicated by the fact that industrial farming techniques mean agriculture is actually depleting carbon from soil, thus reducing its capacity to act as a carbon sink.
According to Hogg and Favoino, this loss of carbon sink capacity is not permanent. Composting can contribute in a positive way to the twin objectives of restoring soil quality and sequestering carbon in soils. Applications of organic matter (in the form of organic fertilizers) can lead either to a build-up of soil organic carbon over time, or a reduction in the rate at which organic matter is depleted from soils. In either case, the overall quantity of organic matter in soils will be higher than using no organic fertilizer.
"What organic fertilizers can do is reverse the decline in soil organic matter that has occurred in relatively recent decades by contributing to the build-up in the stable organic fraction in soils, and having the effect, in any given year, of ensuring that more carbon is held within the soil," they explain.
But calculating the value of this technique to climate change policies is complicated. To refine previous calculations and to take account of the positive and negative dynamics of carbon storage in soil, Favoino and Hogg modelled the dynamics of compost application and build-up balancing this with mineralization and loss through tillage.
Their results suggest that soils where manure was added have soil organic carbon levels 1.34% higher than un-amended soils, and 1.13% higher than soils amended with chemical fertilizers, over a 50-year period. "This is clearly significant given the evaluations reported above regarding carbon being lost from soils, and the increasing amount of carbon dioxide in the atmosphere," they say.
The potential role of compost in reducing greenhouse gases by Enzo Favoino and Dominic Hogg is published on Monday 25 February in a special issue of Waste Management & Research, entitled Greenhouse Gases & Solid Waste Management.
Initial results from a £3.4 million research project by environmental consultancy ADAS are positive about the cost and soil benefits of using compost as a fertiliser. Soil scientist, Susie Holmes, of ADAS, said: "Benefits of compost in terms of cost savings on fertilisers are now significant." The Boxworth winter wheat trial, part of the ADAS research projectThe long-term research project, which was commissioned by Compost Research Limited, began in 2006 and will run through until the 2009 harvest, and is already showing "good long term benefits" for farmers who apply compost to their soil. Ms Holmes told letsrecycle.com: "One tonne of typical green waste is now worth around £7 to £9 per tonne in terms of its major nutrient content alone."She said in some cases, particularly where compost has been made using green waste, it may be worth £10 per tonne for nutrient content thanks to high levels of nitrogen. She added: "The contribution of magnesium, sulphur, and trace elements in compost may give added benefits to some soil typesMs Holmes explained: "The longer term benefits of using compost are something that farmers should also be considering. Not only does compost add to the nutritional status of the soil, especially potassium levels, but the high organic matter content, in particular high lignin content of compost, helps increase the soil organic matter status."In addition to having a high nutritional value, compost also improves water-holding capacity, nutrient-holding characteristics and physical structure, making it easier to cultivate and less prone to erosion. Ms Holmes stressed that the best benefits are in the "long term", saying it can take 5 to 10 years for the true value of compost to reveal itself. But she added that farms taking place in the trial have shown soil improvement since the project began in 2006. She explained that trials at Gleadthorpe, Rosamaund and Boxworth, had all been "a success so far"."Compost is of particular benefit for rotations which include potatoes or other root vegetables because of its high potassium content and its potential to improve water holding capacity of lighter soils."She said early results had shown soil improvement, particularly with levels of potassium and potash and biological activity. She said: "A lot more farmers are interested in compost and some people have not been able to get any. It's a complete change and people are queuing up for it."
Jeremy Jacobs, acting chief executive of the Composting Association (which will be known as the Association for Organics Recycling from August 1) said: "This latest research has provided further data on fertiliser replacement values of composts, which is particularly welcome in light of the spiralling cost of artificial fertilisers."
