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BIOBEDS

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Abstract:

Pesticides found in surface and ground waters are a highly emotive and important subject. Protection of our water supply, with the limit for a single pesticide in water being 0.1 microgram per litre, is in everyone's interest. In the UK, biobeds offer considerable potential to reduce pollution to this very low target for water arising from yard and filling areas. Research has shown that 40-70% of the pesticides found in water come from mixing, filling and other sprayer management operations at the filling site. Therefore, although biobeds focus interest as a concept, minimisation of pesticide discharges at the filling site must initially be investigated. Most farmers have not considered minimisation of potential discharges, although by such action the discharges may often be halved. Initially an approach should be made to minimise the amount of pesticides 'dropped' at the fill area. No one sets out to create this spillage when spraying, but under the pressure of the operation inadvertent drips and spills associated with some wash out and wash down effects do occur. Training of all pesticide users in the correct manner to handle, use and dispose of pesticides and associated wastes, dealing with spillages and keeping pesticide application equipment in good working order are all seen as fundamental to limiting point source pollution on farms. Courses offered through the Voluntary Initiative (VI) have been very successful in meeting this need. In the UK, the VI has been promoted since 2001 when the Government accepted proposals put forward by the farming and crop protection industry to minimise the environmental impacts from pesticides. The programme was developed as an alternative to a pesticide tax which had been under consideration by the Government. By 2006, the programme had met or exceeded the vast majority of its targets. In the light of this, the VI Steering Group proposed to Ministers that The Voluntary Initiative should continue as a rolling two year programme. These proposals were welcomed by the Government. The location, design, management and operation of sprayer filling areas are considered as primary targets to limit point source pesticide pollution. The characteristics of the farmyard surface and associated drainage will control the rate at which any spilt pesticide, washings or waste reaches a water resource. Most sprayer fill areas grew from being where a convenient water supply was at hand. Very few were placed where potential contamination could be minimised and many intercept or contribute contamination to larger areas affected significantly by rainfall, thus magnifying the problem. Securing the fill area by bunding and directing waters through a discreet drain to a tank for disposal or to a lined biobed is key. It may not be necessary to roof the fill area if its size is limited to that sensibly to enclose the sprayer and access around it. A biobed is a hole in the ground, approx 5 m × 4 m surface area and 1m deep with approx 30° batter to the sides and an impermeable liner installed coupled to a through drain. This system allows all liquids to pass from the filling area through the biobed, which is in effect a form of compost 'heap' function. Most Swedish biobeds are of the drive over type where the biobed is directly under a grid on which the sprayer stands during filling. The liner contains the mix of 50% straw, 25% soil and 25% peat-free compost. This has been shown in Swedish and UK trials to be the most successful mix to promote pesticide breakdown. This mixture is mixed and left to mature naturally in a heap for 4 weeks prior to being loaded into the impermeable liner. The surface of the biobed is turfed over. This combination of ingredients works to allow the chemicals to lock onto the straw and to allow the microbial action in the soil to break down the pesticides, as would be achieved within the field condition after normal spraying. In the UK, the drainage water from a biobed, with significantly lower pesticide content is then irrigated to a small area of land. In Sweden, biobeds are not required to have liners and discrete drainage, the drainage water from the biobed mix passes directly into the surrounding soil. In February 2002, three sprayer fill areas and biobeds were built on a large farming enterprise in Lincolnshire which operated agricultural spraying operations from three existing farmyards to assess the performance and practicality of biobeds under UK conditions. This work was funded by Defra and EA (Environment Agency). These systems have been the subject of considerable study, full time over two years and in commercial use since then until mid 2009. The Lincolnshire Agricultural Machinery Manufacturers Association show funded the research from 2003–2007. Additionally, further study has been funded by the UK Pesticide Safety Division.

Document Type: Research Article

DOI: http://dx.doi.org/10.1564/21apr06

Publication date: April 1, 2010

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