IV. CONCLUSIONS There is mounting pressure on farmers to reduce pesticide use. At the same time, farmers must maintain crop yields and THE ROLE OF UNCOMPOSTED MATERIALS, COMPOSTS, MANURES, AND COMPOST EXTRACTS 475 maintain or improve crop quality in order that they can retain their market share. There is increasing evidence that the use of uncomposted plant residues, composts, manures, and compost extracts/teas can help them do this through improvements in soil health and through direct and indirect control of pests and pathogens. In a few documented cases, control of specific pests or diseases using uncomposted plant residues, composts, or compost extracts/teas in conventional agricultural or horticultural systems has been equal to or better than that achieved with synthetic pesticides. However, for many pests and diseases, the level of control that has been demonstrated in glasshouse and field trials is lower than that normally considered acceptable for conventional growers. Commercial and domestic produce buyers may find it difficult to accept that the quality and yield of conventional crops treated in this way are often lower. For organic growers, who have no access to fungicides or other synthetic pesticides, uncomposted plant residues, composts, and compost extracts/teas may provide useful additions to the range of partial disease control solutions to which they have access. Considerable work is required to develop protocols that can be used to ensure predictable and reliable pest and disease suppression or control from organic amendments on economically important temperate crops in different soil types. Some of the recent work has been done on tropical or sub-tropical crops and in different soils and farming systems from those represented in temperate zones. It will be necessary to adapt the techniques and protocols successfully developed or being developed in these climate zones for use in temperate farming systems. Many of the recent reports of improved plant growth or successful disease control using compost teas are based on anecdotal information or commercially sensitive data held by private companies. There is a strong need for independent research to demonstrate the effects of compost teas and to elucidate the mechanisms behind reports of disease suppression or improved plant growth. A great deal of the recent work on composts and compost teas done in the United States has been carried out using input materials that are prohibited or not readily available in Europe. Research is required to assess the quality and diseasesuppressive properties of composts and compost teas prepared from input materials that are cost-effective and readily available to European farmers. REFERENCES Abawi, G. S. and Crosier, D. C. 1992. Influence of reduced tillage practices on root-rot severity and yield of snap beans, 1991. American Phytopathological Society, Biological and Cultural Tests 7: 9. Abawi, G. S. andWidmer,T.L. 2000. Impact of soil health management practices on soilborne pathogens, nematodes and root diseases of vegetable crops. Appl. Soil Ecol. 15: 37-47. .Abbasi, P. A., Al-Dahmani, J., Sahin, F., Hoitink, H. A. J., and Miller, S. A.
2002. Effect of compost amendments on disease severity and yield of tomato in conventional and organic production systems. Plant Dis. 86(2):
156-161. Agrios, G. N. 1977. Control of plant diseases. In: Plant pathology.
4th ed., pp 173-221. Academic Press, New York. Akhtar, M. and Malik, A. 2000. Roles of organic soil amendments and soil organisms in the biological control of plant-parasitic nematodes-a review. Bioresource Technol. 24: 35-47. Albiach, R., Canet, R., Pomares, F., and Ingelmo, F. 2000. Microbial biomass content and enzymatic activities after the application of organic amendments to a horticultural soil. Bioresource Technol. 75: 43-48. .Al-Dahmani, J. H., Abbasi, P. A., Miller, S. A., and Hoitink, H. A. J. 2003. Suppression of bacterial spot of tomato with foliar sprays of compost extracts under greenhouse and field conditions. Plant Dis. 87(8): 913-919. .Anon. 2001. Compost Tea Trials. Cascadia Consulting Group. Final report submitted to Office of Environmental Management, City of Seattle. 8 March
2001. 50 pp. Anon. 2003. A sustainable approach to controlling allium white rot. Agriculture Link (Newsletter for the Agriculture and Horticulture Industries PB8431). Department for the Environment, Food and Rural Affairs, London, UK. Armstrong, G. and McKinlay, R. G. 1997. The effect of undersowing cabbages with clover on the activity of carabid beetles. Biol. Agric. Hortic.
15: 269-277. Aryantha, I. P., Cross, R., and Guest, D. I. 2000. Suppression of Phytophthora cinnamomi in potting mixes amended with uncomposted and composted animal manures. Phytopathology 90(7): 775-782. Baker, K. F. and Cook, R. J. 1974. Biological control of plant pathogens. In: The Biology of Plant Pathogens. pp. 220-285. Kelman, A. and Sequira, L., Eds., W. H. Freeman and Co., San Francisco. .Beare, M. H., Coleman, D. C., Crossley, D. A., Hendix, P. F., and Odum, E. P. 1995. A hierarchical approach to evaluating the significance of soil biodiversity to biogeochemical cycling. In: The significance and regulation of soil biodiversity. Collins, H. P., Robertson, G. P. and Klug, M. J., Eds., Kluwer Academic Publishers, Dordrecht, The Netherlands. .Ben-Yephet, Y. and Nelson, E. B. 1999. Differential suppression of dampingoff caused by Pythium aphanidermatum, P. irregulare, and P. myriotylum in composts at different temperatures. Plant Dis. 83(4): 356-360. .Berner, A., Sousa, H., Koller, M., and M¨ader, P. 2000. Suppressivity of garden waste and manure compost depending on the turning frequency and compost age. Proceedings 13th International IFOAM Scientific Conference, Basel, 5:
- Boehm, M. J. and Hoitink, H. A. J. 1992. Sustenance of microbial activity in potting mixes and its impact on severity of Pythium root-rot of poinsettia. Phytopathology 82: 259-264. .Boehm, M. J., Madden, L. V., and Hoitink, H. A. J. 1993. Effect of organic