Case Study by monkey6


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ReMaDe Kent and Medway is managing a series of WRAP (the Waste & Resources Action Programme) funded trials on top fruit and other horticultural crops in Kent, the ‘Garden of England’, in order to develop the market for compost as a soil improver, and in this trial, as a mulch for young fruit trees. Twelve farms are taking part in the trials growing a wide range of crops, including strawberries, Victoria plums, cherries, Cox and Braeburn apples, blackcurrants and hops. The early establishment of the newly planted trees is critical for maximum growth and fruit yields in later years. One of the main factors affecting their early development is water stress, and organic materials, such as straw, have traditionally been used to reduce the evaporation of water from the soil surface. Weeds also use water in competition with the fruit trees – mulches can suppress annual weed germination, conserving water and reducing the need for herbicides. Compost mulch was sourced from three major producers in the South East – Shelford Composting Ltd near Canterbury, Beddingham Composting in East Sussex and the Tree Fella in Essex – and conformed to BSI PAS 100. Mulch is obtained when compost is screened to between 15 and 40 mm at the end of the eight to twelve week composting process. This fraction, because of its woody nature, has always been considered to be the most difficult for compost producers to market. The project has evaluated all aspects of the mulching approach – from the production of the mulch fraction through to delivery, application methods and tree growth responses. Specialist technical support was provided by The Farm Advisory Services Team (FAST). the compost as a mulch. Sandys farms over 100 acres of fruit, including 60 acres of top fruit – dessert apples, Bramley apples and pears – plus 20 acres of strawberries, including table top growing under Spanish tunnels. He also grows 20 acres of stone fruit – Victoria plums and cherries. The farm has a limited amount of irrigation and therefore relies on natural rainfall for water supply to the majority of the growing trees. Water is critical for mature trees and fruit yields and is of even greater importance when establishing a new orchard with young trees. Traditional practice includes the use of straw as a mulch in order to conserve moisture and to help reduce annual weed growth. Straw application is, however, beset with a number of problems which include windblown losses and disturbance of the straw on the site by rabbits and other animals. This trial set out to compare the effectiveness of the compost mulch against traditional straw application and untreated control rows.

Mount Ephraim Farm
Sandys Dawes of Mount Ephraim Farm, Faversham, Kent, was one of the first of twelve growers in Kent and Medway to trial

The compost was first applied in June 2004 as a band of woody mulch one metre wide and 7 to 10 cm deep, approximately equivalent to 4 tonnes of compost per 100 metres of row. Application along the rows of Victoria Plum trees was accomplished using a side spreader. Ease and speed of mulch application was evaluated for comparison with the straw mulching alternative. The compost mulch is applied on a biennial basis, spreading costs over a two year period.

Regional Market Development Fund

2005 rainfall compared to the 31 year average Data from the FAST weather station, North Street

Key benefits of using compost mulch on young trees: • Water is conserved in the soil • Trees are less prone to water stress • Extension growth is improved • Early yields are increased • Nutrients are slowly released into the soil • Annual weeds are suppressed Sandys Dawes, Mount Ephraim Farm owner, was impressed with the results, though the costs of delivery and application of the compost was of concern. However, ongoing discussions with all participating growers indicated that the costs of applying the compost need not exceed that of applying conventional straw. He said: “Yield of the Victoria plums was good and, moving forward, we will be taking time to evaluate the cost effectiveness of the compost mulch. But we are in no doubt that mulches such as these will be of paramount importance in a future where water applications may be severely restricted or even prohibited completely.” Dr Joe Lopez-Real, ReMaDe Kent & Medway Organics Adviser said: “These results are dramatic and really encouraging. As predicted, it has taken an eighteen month period for the benefits of mulching to be seen in the crop. Not only will the compost continue to act as a moisture retainer, it will also improve the top layers of the soil as it is gradually incorporated by worm activity, thus improving soil structure and supplying valuable slow release nutrients. The suppression of annual weeds will hopefully mean less herbicide usage – good news for the grower and great news for the environment.”

Moisture fluctuation at 10cm depth

During the past eighteen months the treated rows have been monitored for moisture levels, weed growth and tree growth extension in order to evaluate the effectiveness of the mulch on tree establishment. Results have shown clearly that the compost mulch is highly effective at boosting moisture retention properties. Data showed that over the ten month period from January to October 2005, rainfall in five of those months fell markedly below the thirty year average – including the particularly important months of May and June. Throughout this period it was clear that the mulched trees received excellent water stress protection. Annual weeds were also markedly suppressed by the thick mulch layer compared to straw and unmulched rows. The more difficult perennial weeds such as thistles were not controlled by either of the mulches.

Establishment of the trees was measured by collecting data on new shoot development. The shoot lengths for compost and straw mulches were similar and both were superior to non mulched rows, with a 15 percent growth indicating the importance of using mulch materials. The compost mulch produced a 15 percent increase in the number of shoots compared to bare plots and a slight increase of nearly two percent compared to straw. The significance of this slight increase was, however, subsequently translated into a marked improvement in yield of fruit per tree at harvest time, as more shoots produce more buds and, therefore, more fruit. The yield of fruit per tree was 13 percent higher on the compost mulch compared to straw mulch and a dramatic 46 percent increase compared to the unmulched trees.

Contacts and information sources
Compost soil improvers and mulches of good quality, meeting BSI PAS 100, can be found by talking to ReMaDe Kent and Medway or visiting the WRAP website. The Compost Supplier Directory can be accessed at A final report from this project will also be made available on the WRAP website. WRAP The Old Academy, 21 Horse Fair, Banbury, Oxon OX16 0AH Tel: 0808 100 2040 Website: ReMaDe Kent and Medway C/o Invicta Innovations, East Malling Research, East Malling, Kent ME19 6BJ Tel: 01732 876617 Website:

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