Using Compost in Landscaping. Compost Information Package 2 PUTTING COMPOST TO WORK!

Transcription

1 Using Compost in Landscaping Compost Information Package 2 PUTTING COMPOST TO WORK!

2 WRAP (the Waste & Resources Action Programme) is a national Government programme established to promote sustainable waste management by tackling the barriers to waste minimisation and increased recycling. For more information go to or phone Contents 03 Summary of the benefits of compost and its use in agriculture and in field horticulture 05 Introduction What is compost? What is composting? 06 What are the standards for compost? How is compost analysed? 07 What are the characteristics of compost for use in landscaping? 08 What are the potential benefits of using compost? 12 Cost benefits 12 How to use compost Garden bed establishment Turf establishment and top dressing Tree and shrub planting Topsoil manufacture 15 How to buy compost 15 Regulations 15 References Useful contacts Information sources Websites

3 Summary of the benefits of compost and its use in landscaping Compost is a product that is made through the process of composting. In the United Kingdom it is most commonly made from gardeners and landscapers plant trimmings and prunings, but may also include small amounts of other sourceseparated biodegradable materials such as manure, untreated wood or paper and card. Kitchen food materials may also be included, but if they contained meat scraps then the product literature must contain information regarding restrictions on its use where animals graze. These materials are processed under carefully controlled conditions to produce a high quality product, as defined by the British Standards Institution s Publicly Available Specification for Composted Materials BSI PAS 100 (2002). Compost conformity should be independently assessed and verified through a certification scheme such as that managed by The Composting Association. These composts are very different from wholly manure based composts, spent mushroom compost and sludges and must be used differently. Compost should be screened through a maximum screen size of 75 mm for a mulch grade. Composts for use as a backfill mix, or as a soil improver, should be screened to no more than 25 mm, and compost for top dressing turf should be screened to at least 10 mm, but preferably 5 mm, especially for finer grasses. Landscaping 03

4 Compost contains plant nutrients and organic matter. These ingredients have beneficial effects when applied to the soil. Compost contains slow release nitrogen, phosphate and sulphur. It contains good amounts of readily available potash plus smaller but useful amounts of magnesium, calcium and trace elements. Compost has a small neutralising value and is about 10% as effective as limestone, tonne for tonne of dry matter. Compost can therefore stabilise soil ph and reduce the acidifying effects of inorganic nitrogen fertilizers. The organic matter in compost is able to confer many benefits including: increased nutrient levels reduced nutrient losses and improved cation exchange capacity better plant survival and growth reduction in soil compaction improvement in soil water holding capacity increased microbial activity increased soil temperatures improved root growth reduction in plant deaths improved plant quality erosion and weed control moisture conservation Compost also contains beneficial microorganisms. These are able to contribute to a healthy soil in terms of improved nutrient cycling and plant disease suppression. Different particle size grades of compost are available for the range of landscaping operations to which it can be applied. For example, coarser, more woody fractions are necessary to act as a stable, effective and long-lasting mulch, while applications to turf must be finely screened to allow for dispersal of the particles down through the grass blades and into the soil. The application rates for compost will vary, depending on end use. A 50 mm layer of compost worked into the soil to 150 to 200 mm acts as an effective soil conditioner. Compost used in backfill mixes at 30% inclusion can aid plant establishment and survival especially where soil structure is poor or dry conditions prevail, although lower compost application rates may be applied according to plant species. Mulches should be applied at 25 to 75 mm depth. On turf, top dressings can be 6 to 12 mm deep and brushed and watered in to the sward. Topsoil can be made from poor soils and recent compost analysis results from the supplier should be used in order to apply and utilise the compost correctly. 04 Landscaping

5 Introduction Compost is a natural product made by composting biodegradable materials under managed conditions. In the United Kingdom, plant materials from households, parks and gardens are the main raw materials and, when not composted at home, may be composted at community sites or large scale composting facilities. They are processed under carefully controlled conditions to produce a high quality product, as defined by the British Standards Institution s Publicly Available Specification for Composted Materials BSI PAS 100 (2002). Compost conformity to PAS 100 should be independently assessed and verified through a certification scheme such as that managed by the Composting Association. These composts are very different from wholly manure based composts and sludges and must be used differently. These guidelines help you to obtain the correct product grade for your requirements and help you to use compost wisely and profitably. What is compost? Compost is a different product to manures and slurries that are used on land, and is defined in the BSI s PAS 100. It is a product in its own right that is safe to use in the environment with beneficial properties that can be used to advantage in landscaping. Although compost is mainly made from domestic garden or landscapers tree and shrub prunings and grass cuttings, it may also contain some small amounts of paper or card, untreated wood or animal manures. Properly treated kitchen food wastes may also be included at approved composting sites. The compost supplier will have records of the types of materials used to make the compost. The product literature must contain information regarding restrictions on its use and record keeping where animals graze or crops are cut for fodder. What is composting? Composting is a process of controlled biological decomposition of biodegradable materials under managed conditions. Conditions within the composting heaps are controlled by various means to ensure there is sufficient air, moisture and high temperatures within each heap such that, over time, this results in compost that will have beneficial effects when added to soil or container-mixes that support plants. Vermicomposting, which relies on specific worm species, can also produce high quality vermicomposts although they are not covered by PAS 100, which only deals with high temperature composting. High temperatures and moist conditions sustained during managed composting processes ensure that weed seeds and plant, human and animal pathogens are destroyed. The compost will be stable such that plant pathogens cannot become re-established again after mixing with the soil. This is because the readily biodegradable materials will have been transformed into the building blocks that become soil humus and also because a multitude of beneficial microorganisms are present that can out-compete the plant pathogens. Landscaping 05

6 What are the standards for compost? Biodegradable, source separated materials are processed under carefully controlled conditions to produce a high quality product, as defined by the British Standards Institution s Publicly Available Specification for Composted Materials BSI PAS 100 (2002). Compost conformity to PAS 100 should be independently assessed and verified through a certification scheme such as that managed by the Composting Association - look for the certification mark. Full details of the PAS 100 are available from the British Standards Institution (BSI). Information is also available from the Composting Association at or from the Waste and Resources Action Programme (WRAP) at How is compost analysed? Compost samples should be tested by laboratories that use the methods specified in BSI PAS 100. Most of the methods are for soil improvers and growing media, such as those made from or including composts. These methods are different from those used for soils. The Composting Association maintains a list of suitable laboratories. CASE STUDY 01 When I arrived at Compton Acres in 2002 I found that the light sandy soil was extremely hungry and in need of organic matter. The first garden to be refurbished was the Italian Garden, a 200 x 100 metre plot with a raised terrace. I d used Eco Composting s Eco-mix previously and knew it would provide strong, uniform growth patterns for our new plantings. Compost has high nutritional benefits that result in a noticeable reduction of plant wastage compared to other non-compost products. Compton Acres is a high profile garden with a reputation to uphold; it has to look good and be top quality 365 days a year. Our professionalism is reinforced by everything from the aesthetic appeal of surface mulching compost and healthy plants throughout the gardens, to the reassurance that we are using a reliable, quality product. KEY FACTS ABOUT COMPTON ACRES 10-acre collection of themed gardens in Poole, Dorset Over 200,000 visitors a year Full range of ornamental garden plants including hardy and semihardy 60 m 3 of TCA accredited compost used to date Chris Allen, Curator, Compton Acres 06 Landscaping

7 What are the characteristics of compost for use in landscaping? These are some recommended properties of a good compost for use in a variety of landscape applications. Parameters Reported as (units of measure)recommended Range Application ph ph units (1:5 water extract) 8.7 maximum Soil improver Turf Backfill mix Electrical ConductivityµS/cm or ms/m (1:5 water extract) Soil improver 2000 µs/cm maximum Turf establishment or 200 ms/m maximum Backfill mix 2500 µs/cm maximum or 250 ms/m maximum Turf top dressing 3000 µs/cm maximum or 300 ms/m maximum Topsoil blending Moisture Content % m/m of fresh weight All uses Organic Matter Content % dry weight basis > 25 Soil improver Turf Backfill mix > 30 Mulch Screen aperture size mm 5 maximum Fine turf top dressing 10 maximum General purpose turf top dressing 25 maximum Soil improver Turf establishment Backfill mix 75 maximum (but with no Mulch more than 25% of the material < 10 mm in size) C:N Ratio 20:1 maximum All uses Landscaping 07

8 What are the potential benefits of using compost? Organic matter in soil is essential for soil structure, water holding properties, microbial activity and soil health. Composts can be used to add organic matter to soils and increase the production of soils through many benefits: increased nutrient levels reduced nutrient losses and improved cation exchange capacity better plant survival and growth reduction in soil compaction improvement in soil water holding capacity increased microbial activity increased soil temperatures improved root growth reduction in plant deaths improved plant quality erosion and weed control moisture conservation The nutrients in compost reduce the need for inorganic fertilizers. Ref [1] Compost contains significant quantities of the major plant nutrients, such that additional applications of phosphate and potassium fertilisers become unnecessary. However, nitrogen levels are not always high enough for the compost to act as a conventional fertiliser and it is likely that supplemental applications of inorganic nitrogen will be necessary to provide adequate nutrients for plant growth. Supplements should be at a reduced rate, thus reducing conventional fertiliser costs. Composted materials contain the full range of minor nutrients and trace elements, making compost a valuable source of these elements, e.g. zinc, copper, manganese and boron. Many conventional fertilisers do not contain trace elements and products which include them are relatively expensive. As they are needed in small quantities, supplementary applications of trace elements are not required when using compost in planting schemes. The composition of compost will vary according to the materials included and the composting process itself. However, as a general rule compost provides the following nutrient benefits (approximate figures as total nutrient kilogramme per tonne of moist compost based on typical analysis): Nitrogen Phosphate Potash Magnesium Sulphur as N as P 2 O 5 as K 2 0 as Mg as S Composts not only provide valuable organic matter to soils, but also act as slow-release fertilizers for nitrogen and phosphate, and provide a readily available source of potash. Other nutrients are also provided by composts such as, magnesium, sulphur and trace elements. Compost can also provide a valuable source of calcium with a small liming effect (it has up to 10% of the neutralising value of limestone on a dry matter basis) and so 30 tonnes of compost may be as effective as 2 tonnes of limestone. 08 Landscaping

9 Compost also provides the following approximate amounts of plant available nutrients: Depth over Cubic metres Cubic metres Tonnes Tonnes dry matter N P 2 O 5 K 2 0 an area per 100m 2 per hectare per hectare per hectare kg per hectare 6mm 1/ mm 1/ mm mm By comparison inorganic fertilizers provide the following nutrients: Product Analysis Rate N kg/ha P 2 O 5 kg/ha K 2 0 kg/ha potassium sulphate 48% K g/m superphosphate 18% P 2 O 5 70 g/m ammonium sulphate 21% N 70 g/m :15:10 spring turf 35 g/m :10:10 autumn turf 50 g/m Unlike inorganic nitrogen fertilizers, the nitrogen in compost is slow release and not subject to leaching over winter. Compost may therefore be applied in the autumn and all of the nitrogen will remain in the soil to benefit crops in the following and subsequent years. Composted garden and landscaping plant materials tend to be lower in available nutrient content than compost made from animal manures and kitchen food or vegetable materials. The application rate of compost may need to be lowered where composts with higher availabilities of nutrients are used. A guideline as to when the rate should be lowered is given below for various parameters based on water extractable characteristics (1:5 compost:water ratio). Characteristic Use a proportionally lower rate when the analysis is above one of these levels Ammonium + nitrate nitrogen > 200 mg/litre Potassium > 1500 mg/litre Electrical conductivity> 1200 µs/cm or 120mS/m Landscaping 09

10 Reduced nutrient losses and improved cation exchange capacity. Ref [2] Light textured soils have low cation exchange capacities (CEC) and the addition of compost will raise the CEC of these soils. This enables the soil to hold onto nutrients such as potassium and nitrogen which would otherwise leach beyond rooting depth. Better plant survival and growth are observed when soil organic matter contents are raised. Ref [3] Ideal soil conditions are found under long-term grassland and woodland, but most landscaping operations have to deal with very poor soils. Modern varieties only reach their full potential when organic matter levels are high enough. It has been found that additional nitrogen fertilizer cannot compensate when the organic matter is low. This may be because modern plants, many of which are not native, need to establish rapidly and this requires good soil physical conditions for rapid root growth to explore the soil for nutrients and water. Humus content plays a central role in soil structural stability and aggregation and the addition of organic matter will encourage the formation of stable aggregates in the soil. This increases the number and size of the pore spaces in the soil, enhancing the rate at which water can enter the soil, and also increasing the volume of air and water that the soil can hold. The application of organic matter in composted materials will therefore improve soil structure and drainage, reduce bulk density and provide a more suitable rooting environment for plant growth. In addition, the dark colour of compost can raise the soil temperature and will assist germination and improve growth rates in cool conditions. The organic matter in soils may often be less than 2%, for example on brownfield sites, where landscaping operations are to be carried out. For good plant growth, rooting conditions in the soil need to be favourable. Plant roots need air, water and nutrients plus a firm anchor to support the top growth. Soil organic matter is essential for the provision of these elements and should be raised to at least 4 5%, and higher for some soils, depending on soil texture (the proportions of sand, silt and clay). Compost is able to provide organic matter in a relatively stable form that can raise the soil organic matter levels and provide benefits described below. This results in improved plant survival, growth, quality of plants and cost savings. Compost improves soil structure. Ref [4] Many experiments have shown that organic matter improves the aggregate strength of soils. This means that the soil is more resistant to compaction and that roots can penetrate more easily to find nutrients and water. Heavy soils are more easily worked when the soil organic matter is high. The available water holding capacity of soil is raised. Ref [5] As part of the benefit of improved soil structure, the infiltration of rainfall and irrigation water is improved and the soil water holding capacity is increased, especially on light soils. Thus the duration or frequency of watering after planting can be reduced, leading to labour savings. Plant survival is also improved and this leads to lower maintenance costs 10 Landscaping

11 Mulching with compost can control erosion and weeds. Ref [6] On the light soils the erosion risk from wind and water is high. This is especially so where organic matter levels are low and soil aggregation poor. Application of compost to condition the soil can rectify the situation and spot applications can be used to reduce erosion in susceptible areas. Compost mulches act as a physical protective barrier to the soil surface. They can provide enormous benefits to landscape plantings through weed control, moisture conservation, drainage and erosion control. Chemical herbicides can be expensive and damaging to the environment, and herbicide resistance is increasingly commonplace. Compost mulches provide a cheap, environmentally-safe means of weed control which reduce costs and labour inputs. In addition to their direct benefits, mulches improve the condition of the soil over time as they become incorporated into the site soil. The microorganisms in compost increase soil aggregation. Ref [7] The organic matter in compost is populated by microorganisms which supplement those already present in the soil. The microorganisms utilise organic matter as an energy source and release polysaccharides and humic substances that help form soil aggregates and improve the structure of soil. The microorganisms in compost recycle nutrients from organic matter. Ref [8] Microorganisms cycle nutrients in the soil and release nutrients to plants from organic matter. Annual applications of compost can lead to a significant increase in soil enzyme activity. This activity of the enzymes is related to the rate of recycling of nutrients. The microorganisms in compost help to suppress soil borne diseases. Ref [9] Soil borne plant pathogens may be suppressed in soil when the correct microorganisms are introduced into the soil. This suppression may be caused by competition, antibiosis, parasitism or induced systemic resistance but no single mechanism can be clearly identified as being responsible. Plant losses due to soil borne diseases can be substantial, expensive and often visually unattractive. Landscapers have been encouraged to use chemical measures in the past, but attitudes are changing to these management practices. Alternative, non-chemical methods are increasingly being sought. Composts are biologically active and contain a complex mix of microorganisms which have been shown to suppress a number of plant pathogen species including Phytophthora, Pythium and Rhizoctonia under certain conditions. CASE STUDY 02 Turf trials in the UK have demonstrated the advantages of using compost as a dressing. In order to encourage Essex-based sports turf managers and groundsmen to use compost, ReMaDe Essex conducted a trial to investigate how well compost topdressing compares with a standard topdressing mix used on many golf courses see The treatments were applied to areas of a tee and a fairway to see what effect the application would have on the different turf areas. Assessments demonstrated that the compost treatments outperformed the standard sandbased topdressing in terms of improved turf grass density, vigour and foliage colour. Following on from these trials large scale applications were made on various golf courses in East Anglia including The Epping Golf Club. Neil Sjoberg, The Epping golf course manager said, "we were keen to participate after attending the demonstration event at Lexden Wood Golf Club. We have since found that using compost has benefited fairway turf and improved the soil structure on the course. We have seen a noticeable improvement on the treated side of the fairways especially when playing iron shots". Landscaping 11

12 Cost benefits Although compost purchase and application is a cost to a landscape project, the benefits of using compost have cost-saving implications. Fertilizer costs can be reduced as compost contains most of the nutrients required by plants for many situations. When used properly, compost can aid the survival of plants in a planting scheme saving replanting costs. This is because the soil improvements mean that light soils will hold more water for plant survival through dry periods, and heavy soils with have a better soil structure to aid root growth. Mulches applied to beds and round trees can save herbicide costs and reduce the competition caused by weeds. Organic matter in compost also holds the beneficial microorganisms that can help suppress plant diseases which can reduce the survival of newly planted specimens. How to use compost The selection of different grades of compost is necessary for the range of landscaping operations to which it can be applied. For example, coarser, more woody fractions are necessary to act as a stable, effective and long-lasting mulch, while compost for application to turf must be finely screened to allow for dispersal of the particles down through the grass blades and into the soil. The site drainage must be adequate before works take place. Plastic drainage tubes, gravel filled holes, and other methods can be used to assure proper site drainage. Subsoils should be ripped, where necessary, when the soil moisture content is suitable, i.e. not too wet or too dry. Planting bed establishment New planting schemes are often sited on nutrient poor soils which have been depleted of organic matter. In many cases, the soil has been disturbed following building or construction. In order to create a suitable substrate for the plants to root into, the soil needs to be enriched with organic matter to improve the soil properties. Most grades of compost are suitable for use as a soil amendment, but the compost application rate will vary, depending on soil conditions. It is necessary to have a soil analysis carried out as this will help to determine application rates. Typical rates are usually a 50 mm layer, which is mixed into the top mm of the soil. This gives an incorporation rate of approximately 20-30% by volume. Lower inclusion rates may be necessary for salt-sensitive crops such as Primula, or where composts with higher salt levels (expressed as electrical conductivity) are used. Higher inclusion rates, up to 100 mm or more, may be required if the recipient soil is particularly poorly structured or has been depleted of nutrients. Once the compost inclusion rate is chosen, a blend of soil and compost can be produced and analysed prior to planting. This will identify the new soil characteristics, including soluble salt and organic matter content, as well as identify the appropriate nitrogen fertiliser rate and ph adjustment necessary for optimal plant growth. Soil amendment Compost should be evenly spread across the soil surface and then thoroughly mixed in with the amounts required based on soil conditions and analysis. The treated area can be raked smooth, if necessary, and should be irrigated if conditions are dry. If ph adjustment is required, lime or sulphur can be added to the soil prior to incorporation of compost, as can any additional nutrients. However, where possible, it is more beneficial to apply these components after the compost has been incorporated and the new soil analysed. When planting is completed, water the plants in thoroughly. 12 Landscaping

13 In subsequent years, compost may be applied at mm depth as a mulch, or raked into the soil, replacing the need for any additional fertilisers. Container planting Soils modified for ornamental planting mixes should contain at least 5% organic matter. By using compost as the organic matter source, landscapers get the added benefits of various macro and micronutrients, a stabilised ph, and a supply of beneficial microorganisms. Planter mixes can contain up to one third compost depending on the salt (expressed as electrical conductivity) and nutrient content of the compost. At high inclusion rates many perennial and annual species will not require fertiliser. However, gross feeders should be given additional nitrogen. Care must be taken with ericaceous subjects (e.g. camellias, heathers, rhododendrons) as soils above ph 6 will adversely affect their growth. A lower rate of compost, e.g. 10%, can be used as long as the other components in the mix do not have an alkaline ph. Turf establishment and top dressing Compost can be used in a variety of situations, including residential and commercial lawns, sports grounds, athletic fields and golf courses. Excellent results can be achieved when using compost both to establish or renovate turf. It is important to ensure that the compost you use is of the right quality. It should not contain any stones or contaminants and should be well decomposed. Turf establishment - seeding and turfing Compost should be applied mm deep and then incorporated to an approximate depth of mm. The compost application rate will vary depending on the soil conditions, compost characteristics, and turf species to be established. A soil analysis test is recommended to establish the quality of the site soil. If the soil is poor and the compost has low nitrogen availability, additional inorganic nitrogen fertilizer may be applied to the seedbed. Once the compost has been incorporated, a proper seed bed should be established and the seed lightly brushed into the surface using a drag mat or rake. Turf may be applied directly on to the soil surface either manually, or with specialised equipment. Once planting is completed, the area should be watered on an ongoing basis to ensure adequate rooting. Turf topdressing Compost can be used as a top dressing for all areas of turf, either as a component of a mix, or on its own. Compost can be blended with various other materials such as sand and loam to produce a product that matches requirements, especially closely mown fine turf and sanddominated, free draining sports turf rootzones. Apply to the turf surface at a rate of 6 to 12 mm depth (30 to 60 tonnes per hectare), brush in and water, if necessary. Use the lower rate on sports turf and lawns and the higher rate on low maintenance grass and roadside verges. Core aeration techniques can also be used prior to application. The compost should be moist but flowable to facilitate application. Divot repair Divots on golf courses can be fixed effectively using a blend of compost and grass seed mix. The compost contains nutrients and holds moisture, and the dark colour can help to absorb heat from the sun, speeding up germination in cooler periods. Tree and shrub planting For use in backfill mixes the compost should be well decomposed. Such composts can eliminate the need to add major nutrients during planting unless the soil is poor and additional nitrogen is required. Composted materials contain the full range of minor nutrients and trace elements. The soluble salt content (expressed as electrical conductivity) of compost used in backfill mixes may vary and maximum salt tolerance levels are soil and species dependent. Soluble salts should not be a significant problem with most woody ornamentals. However, care should be taken when bare root, ericaceous, and other salt-sensitive crops are planted. Accredited compost producers will supply details of recent chemical and physical analysis and this should be used in conjunction with an analysis of the site soil. CASE STUDY 03 Robert Moody Managing Director, Jack Moody Ltd We started business as a landscaping and horticultural company, and we have always been concerned with using high quality products. Most of our contracts are with local authorities and they were increasingly demanding sustainable landscaping solutions. It followed naturally that we should move into composting ourselves, and we have worked closely with the Composting Association to achieve compliance with the standard for compost. I know that landscape architects and designers have been cynical about using organic waste derived compost in the past but now they can be confident in obtaining a consistently high quality product. It is up to all end users to keep demanding quality and drive the need for accreditation through the composting industry. The commercial benefits of using compost are numerous from improved plant development to easier application and maintenance. We have noticed an increase in plant growth when we use the compost as a soil conditioner on poor quality ground, and a decrease in the need for replanting. We use it on all our landscaping contracts as we think that it offers our clients real value for money. KEY FACTS ABOUT JACK MOODY LTD 35,000 m 3 of TCA accredited compost produced in ,000 m 3 used for their own landscaping contracts 25,000 m 3 bagged and distributed to garden and DIY centres Landscaping turnover approximately 7.5 million per annum Key landscaping clients include: Birmingham City Council; Stafford Borough Council; and Lichfield District Council Landscaping 13

14 The compost should have a moisture content between 35 and 55%. Compost with a high moisture content is expensive to transport and difficult to handle. Compost low in moisture can be dusty, absorbs water less easily, and can aggravate water stress in the tree or shrub on planting. The inclusion rate of compost in the backfill mix will vary, based on the species to be grown and the characteristics of the soil to be blended. Between 25 and 50% compost by volume, blended with the native soil, has been widely used, but the preferred inclusion rate is approximately one third compost by volume. Prepare the root-balled, containerised, or bare root plants in accordance with the industry standard methods before planting. The planting hole should be slightly deeper than the root ball and two to four times its width. The soil removed from the planting hole should be thoroughly mixed with compost at a rate of two parts soil to one part compost unless it has a high salt content. Use this material to backfill around the root ball, firming occasionally to remove air pockets. The trees or shrubs should then be watered in and preferably mulched to conserve moisture and suppress weed growth. Mulching Mulching provides an attractive and cost-effective means of retaining soil moisture, controlling weed growth and preventing soil erosion. Coarser grade composts which contain larger woody fragments are preferable for use as mulches as they do not decompose as readily and remain in place for longer. The surface of coarse materials dries out rapidly, inhibiting weed seed germination. Therefore avoid including excessive amounts of fine particles in the mulch. Composts with higher soluble salt contents should be used with caution on herbaceous and salt-sensitive plants. Similarly, caution should be used when applying composts with a high ph where acid-loving species are planted. Apply the compost evenly on the surface of the garden bed or around the trees and shrubs, creating a continuous mat of compost mulch over a weed-free surface. Compost should be applied to a depth of 25 to 75 mm beneath trees, shrubs, and other plants in garden beds and planting schemes. Avoid placing mulch against the tree trunk or main leader of the shrub, as this can cause damage to the protective bark layer of the stem. Once applied, the mulch may be watered-in to help keep it in place and to help leach out any excess salts. If the compost is high in soluble salts, reduced amounts should be applied and the mulch should be well watered. The control of growing weeds is one of the most important benefits of mulches. Prior to the development of chemical herbicides, mulches were widely used to control weeds. To suppress weeds physically, a 100 to 150 mm thick mulch layer may be needed. In general, the germination of weed seeds declines as burial depth increases. Additionally, organic mulches gradually improve soil physical and biological properties as they decompose and become incorporated into the soil, behaving in the same way as a soil amendment over time. Topsoil manufacture Compost can be mixed with poor quality soil and subsoil, as well as other inert materials, to add organic matter and plant nutrients and bring the analysis of the soil up to the equivalent of a natural topsoil. The characteristics of various soils are described in BS 3882:1994 and premium grade requires a minimum of 5% organic matter and that the soil texture, stone content and nutrients fall within certain limits. The lighter loam textured soils are preferred as they are easier to mix and handle, and plant growth is generally better than in soils dominated by the silt and clay fractions. Regulations regarding the development of brownfield sites must be followed and soil analysis undertaken to ensure that Soil Guideline Values (SGVs) for potentially toxic elements are not exceeded. Invasive, non-native weed species must also be disposed of according to regulations. Blending should be carried out on a suitable hard standing or compacted surface when the weather is suitable and the soil is at the correct moisture content. 20 to 30 m 3 of compost may be required per 100 m 3 of soil to raise the soil organic matter content by 1%. However, soil and compost analysis should be used to calculate the ratios required based on a dry weight basis and then converted to volumes for ease of mixing. To check the suitability of a mix, a small amount of the mix should be made and analysed prior to any large scale operations to ensure the mix is correct. 14 Landscaping

15 How to buy compost The Composting Association Certification Scheme is the only UK scheme that gives third party assessment and verification of conformity with the BSI Publicly Available Specification for Composted Materials (BSI PAS 100). TCA certified composts are quality assured, traceable and safe. There are a number of composting companies that can supply quality assured compost manufactured to PAS100. For a list of certified suppliers, visit the WRAP website on or call the WRAP Freephone Helpline on Alternatively, contact the Composting Association on Regulations Animal By-Products Regulations 2003 The Animal By-Products Regulations 2003 apply to compost made from catering wastes animal by-products that may be applied to agricultural land where animals graze or have access, or fodder crops are grown and fed to animals within certain time periods. More information is available from The full technical report that forms the basis of this technical information package will be available on the WRAP website from March The report provides detailed scientific evidence to support the benefits claimed in this information package, further to the references given below. References [1] Data sources: TCA and Remade Data Open Windrow GROWS Project Compost Vegetable Waste & Manure Wyvern Compost , HDRA Report [2] Mamo, M., C.J. Rosen, et al (1999) Nitrogen Availability and leaching from soil amended with municipal solid waste compost Journal of Environmental Quality 28(4): Horst, H., Arning, M et al (1999) Modelling long-term compost application effects on nitrate leaching Plant and Soil 213: [3] Alexander, R. (1999) Compost markets grow with environmental applications Biocycle 4: [4] Pagliai, M., Guidi, G. et al (1981) Effects of sewage sludges and composts on soil porosity and aggregation Journal of Environmental Quality 10(4): Pinamonti, F. (1998) Compost mulch effects on soil fertility, nutritional status and performance of grapevine Nutrient Cycling in Agroecosystems 51(3): [5] Aggelides, S.M. & Londra, P.A. (2000). Effects of compost produced from town wastes and sewage sludge on the physical properties of a loamy and a clay soil. Bioresource Technology 71(3): [6] Pinamonti, F. (1998) Compost mulch effects on soil fertility, nutritional status and performance of grapevine Nutrient Cycling in Agroecosystems 51(3): Ozores-Hampton, M., Obreza, T.A. et al (2001) Mulching with composted MSW for biological control of weeds in vegetable crops Compost Science & Utilisation 9(4): [7] Blake, L.B., PC (2002). Soil organic carbon forms responsible for structure aggregation, IACR-Rothamsted [8] Wood, M. (2001) Phosphotase activity as an indicator of soil quality Personal Communication [9] Hoitink, H.A.J., Stone, A.G. et al (1996) Suppression of plant disease by composts The Science of Composting A4: de Ceuster, T.J.J. and Hoitink, H.A.J. (1999) Using Compost to control plant diseases Biocycle 6: Landscaping 15

16 Information sources The BS 3882:1994 Specification for topsoil is available from the BSI. Refer to the Wildlife and Countryside Act 1981 and for information on invasive, non-native weeds, the Environment Agency website at: yourenv/eff/wildlife/213341/509287/ BS 10175:2001, Investigation of Potentially Contaminated Sites Code of Practice BS 5930:1999, Code of Practice for Site Investigations CLEA Model and Soil Guidance Values (SGVs) for soil potentially toxic elements (PTEs) - for additional guidance, refer to the following websites: y/index.htm and Waste management licensing information is available from the Environment Agency Useful contacts British Standards Institution The Composting Association Waste and Resources Action Programme (WRAP) Web sites DEFRA The Environment Agency SEPA The Highways Agency The Joint Council for Landscape industries British Association of Landscape Industries Institute of Landscape and Amenity Management Nation Building Specifications NBS Institute of Groundsmanship Groundwork The Royal Horticultural Society RHS The Horticultural Development Council Sports Turf Research International The National Farmers Union Horticulture Research International Waste and Resources Action Programme The Old Academy 21 Horse Fair, Banbury Oxon OX16 0AH Tel: Fax: info@wrap.org.uk Creating markets for recycled resources