Developing the use of compost in agriculture
Aim
To investigate the use of green waste compost on agricultural land by assessing its effect on plant growth, soil nutrient status, soil structure and impact on the environment
Background
During the last 10 years there has been a dramatic increase in the extent and development of composting operations to recover value from organic municipal wastes. From less than five operations in 1990, it is estimated that today there are more than 70, composting in excess of 300,000 tonnes of waste per annum.
In line with developments in other European countries it is now generally accepted in Britain that if urban waste is to be recycled it must be segregated at source. Most producers have therefore started by composting just green waste (botanical wastes from private and public gardens, parks and other civic amenity sites) since collection of this material can be easily achieved by using skips for green waste only. Organic kitchen wastes are being introduced gradually as rigorous source-segregation schemes are put into place. As a result, the composts that are produced today are of high quality with low levels of contamination with regard to both potentially toxic elements (heavy metals) and inert fragments such as glass, metal and plastic.
Today, most composting initiatives are marketing their product as soil improvers, primarily within the local hobby gardening sector. In the future it is likely that it will be used for landscape purposes but in the long term the most important market will undoubtedly be in agriculture. It is, therefore, important to develop systems whereby municipal compost can be safely returned to agricultural land. This will benefit the environment by reducing the problems associated with the land filling of waste, but also by helping to close the cycle of organic matter and nutrient elements and thus the development of truly sustainable agricultural systems.
Approach
This study consists of a series of field trials studying the effects of green waste compost on plant growth, yield, soil nutrient status, soil structure and impact on the environment. Particular emphasis is placed on assessing the release of nutrients from the compost.
A field trial has been set up within an organic system at HDRA in which the effects of municipal composts will be compared with those of FYM, poultry manure and cattle slurry. The design includes annual and single applications at several rates with the effects being carefully monitored over a period of four years. A sequence of field vegetables will be grown and assessments will be made of plant growth, yield, pest and disease problems. The release of nutrients from the compost will be measured, focusing specifically on the release of nitrogen. During the winter period nitrate leaching will be quantified by means of ceramic cup sampling. The possibility of changes in soil structure and water retention will also be investigated.
In addition, on-farm trials are being conducted at two sites in Somerset. One site is on an organic farm, where a total of five fields are monitored. In each of the fields compost is applied as appropriate for the rotation and the effect of the compost is to be compared with the standard practice on the farm. A wide range of crops (including grassland) will be grown in the fields during the four years of the study. The other site is on a conventional arable farm where compost is applied annually, both on its own and in combination with reduced levels of artificial fertilisers. This trial will be monitored for a period of five years.
All of the composts and manures used in this study are subjected to full quality examination under HDRA's Compost Analysis and Testing Service (CATS). This includes assessments of: plant nutrients and organic matter; physical characteristics; levels of contamination with potentially toxic elements (heavy metals), inert fragments (glass, metal and plastic) and weeds; contamination by pathogenic organisms; plant growth in bioassays. The results of these tests are used to assess the environmental impact of using the composts, e.g. rates at which heavy metals accumulate in the soil.
Finally, the results of these experiments will be used to assess the financial value of municipal compost to individual farm businesses.
Dissemination of results
The information from this study will be used to provide advice and recommendations to farmers on the use of compost on agricultural land. The findings will disseminated at Open days and Workshops, through technical articles in the farming press as well as through publications in scientific journals.
This research project is led by HDRA. For further details please contact: Dr Francis Rayns, International Research Department, The Henry Doubleday Research Association, Ryton Organic Gardens, Coventry CV8 3LG. Telephone 024 76303517 Email: research@hdra.org.uk
Jim Ballance, Commercial Manager for Wyvern Waste Services Ltd, Chiltern House, 15/17 Silver Street, Taunton TA1 3DH. Telephone 01823 324194
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