ABSTRACTS Contributed Papers (Oral and Poster) Colloquia Workshops 91st Annual Meeting of the American Society for Horticultural Science Oregon State University, Corvallis 7-10 August 1994 The Abstracts that follow are arranged in numerical sequence by the abstract number. For Poster Sessions, the number preceded by PB (i.e., PB XXX) indicates the poster board number on which the poster will be mounted. Abstracts for Oral Sessions, Colloquia,and Workshops are grouped by sessions. To determine when a paper is to be presented, check the session number in the Program Schedule or the Conference at a Glance charts. The author presenting the paper is indicated by an asterisk. 12 ORAL SESSION 1 (Abstr. 001-008) Vegetables: Cover Crops/Culture and Management 001 COLLABORATIVE LEARNING AND PARTICIPATORY ON-FARM RESEARCH: COVER CROPS ANDVEGETABLE PRODUCTION SYSTEMS John M. Luna*, Daniel Green-McGrath, Ray William. Stefan Seiter and Tom Ten as. Department of Horticulture, Oregon State University, Corvallis,OR 97331. A participatory, on-farm research project was initiated in 1992 in an effort to enhance mutual learning, knowledge, and experience of integrating cover crops into western Oregon vegetable production systems. A major goal of the project was to include growers, agribusiness representatives, governmental agency, Extension and university re- searchers in a collaborative learning process, emphasizing grower participation in the design and implementation of on-farm research and demonstration projects. To facilitate this participation from the planning stage forward, four “focus sessions” were hosted by lead farmers in different areas of the Willamette Valley to define growers’ needs and interests relating to on-farm research and demonstration trials. Based on individual growers’ specific experimental objectives, cover crop evaluation trials were established on ten farms. Typically on each farm, 5 to 10 cover crop species or mixtures (grain and legume) were planted in large plot strips. Twenty five different cover crop species, varieties, and mixtures were planted. Seasonal cover crop biomass and nitrogen accumulation rates were determined, with cover crop impacts on crop yields and economic returns evaluated at selected sites. 002 HAIRY VETCH COVER CROP PROVIDES ALL THE NITROGEN REQUIRED BY THE TOMATO CROP Aref A. Abdul-Baki* and John R. Teasdale, U.S. Department of Agriculture, Agricultural Research Service, Vegetable and Weed Science Laboratories, Beltsville, MD 20705-2350 Nitrogen requirements by fresh-market field tomatoes (Lycopersicon esculentum Mill.) were determined on plants grown in a hairy vetch mulch (HVM) or in black polyethylene mulch (BPM). Nitrogen treatments were 0, 56, 112, and 168 kg/ha delivered weekly through the trickle system. Yields in BPM increased significantly with higher applications of nitrogen from 54 to 91 tons/ha and chlorophyll content of fully expanded leaves increased from 7.8 to 11.3 OD 664 per 100 mg fresh weight. In contrast, neither yield nor chlorophyll content of leaves increased significantly by adding nitrogen. The 0 nitrogen treatment in HVM yielded 89 ton/ha and chlorophyll content was 13.5 OD 664 making it equivalent to those in BPM that had received 168 kg nitrogen/ha. The results suggest that hairy vetch can provide all the nitrogen required by the subsequent tomato crop and produces high yields and vigorous plants. 003 SYSTEMIC IMPACTS OF NON-CROP RESIDUES ON PEST MANAGEMENT IN SNAP BEAN PRODUCTION. Ed Peachey* and Ray William, Horticulture Dept., Oregon State University, Corvallis, OR 97341. Altering the physical or chemical nature of the crop production environment through introduction of cover crops or other non-crop vegetation may amend the impact of various pests on vegetable crops. Current work is focused on the interaction of cereal cover crops and respective management systems with weed emergence and growth, white mold (Sclerotinia sclerotiorum) incidence, symphylan (Scutigerella immaculata) population dynamics, soil food-web structure, and crop yield in snap bean production systems. Research has HORTSCIENCE, VOL. 29(5), MAY 1994 427