SUSTAINABLE POTATO CROPPING SYSTEMS FOR IRRIGATED AGRICULTURE IN THE PACIFIC NORTHWEST
Location: Vegetable and Forage Crops Production Research
Title: FALL PLANTED COVER CROP TRIAL IN FOUR YEAR CROP ROTATION
Submitted to: Ecological and Organic Farm Management Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 1, 2004
Publication Date: February 1, 2004
Citation: BOYDSTON, R.A., COLLINS, H.P., ALVA, A.K., HAMM, P., RIGA, E. FALL PLANTED COVER CROP TRIAL IN FOUR YEAR CROP ROTATION. ECOLOGICAL AND ORGANIC FARM MANAGEMENT WORKSHOP PROCEEDINGS, WILSONVILLE, OR. WASH. ST. UNIV. CENTER FOR SUSTAINING AGRIC. AND NAT. RESOURCES. FEB 2004. p. 19.
A long term field trial evaluating four cover crop treatments in a four year crop rotation of potato-winter wheat-sweet corn-sweet corn was initiated in the fall of 2000. Cover crops include sudangrass, white mustard, oat-hairy vetch mix, and winter wheat. A fallow and a fallow-fumigated treatment is included that is fumigated with metam sodium and 1,3-dichloropropene only in the fall preceding potatoes. Each cover crop treatment is being evaluated for pest suppression (disease, nematode, and weeds), effects on soil microbial diversity and function, and nutrient cycling at Paterson, WA. Crop yield, cover crop growth and biomass, free living and parasitic nematode populations, weed density and species composition, soil borne disease incidence, soil microbial communities and function, and nitrogen mineralization and cycling are being determined. Fumigation has reduced early season weed densities in potato. Early season weed emergence in potato or sweet corn occasionally suppressed following white mustard, oat-vetch, or winter wheat cover crops. Herbicides have reduced weed densities much more than cover crop treatments. No change has been noted in plant parasitic and free living nematode populations or soil borne diseases among cover crop treatments. Fumigation and mustard cover crop treatments have reduced soil fungi and soil pathogens, but had only minor effects on general soil microbial populations and their functions. Sudangrass requires planting no later than mid August to obtain maximum biomass. White mustard has produced the greatest amount of biomass planted from August 15 to September 1. Removing wheat straw and fertilizing with nitrogen has improved cover crop stand establishment when following wheat harvest. Oats and hairy vetch can be planted in September and still produce adequate biomass through the winter. Wheat seeded from September to October, established easily, provided soil cover, and was the least expensive seed. This is a long-term study and the effects of cover crop treatments will continue to be investigated through at least two cycles of the 4-year crop rotation.