Interseeding to improve winter cover crop establishment and efficiency in processed vegetable production in the Willamette Valley

View the project final report

• 2016 annual report

Commodities

• Agronomic: grass (misc. annual)
• Vegetables: cabbages, cauliflower, cucurbits, greens (leafy), sweet corn

Practices

• Crop Production: catch crops, cover crops, intercropping
• Education and Training: demonstration, participatory research

Cover crop establishment following processed vegetable culture in Western Oregon is a challenge because harvest often occurs late into the fall. Soil may already be saturated from fall rains, and the combination of wet soil and crop residue on the soil surface precludes tillage that benefits cover crop establishment. Late harvests also limit the diversity of cover crops that can be planted; legumes do not establish well if planted after September 15 in typical years. A few growers have begun direct-seeding (no-till planting) cover crops in the fall so that they can minimize soil disturbance and reduce energy use. They also may be attempting to limit tillage so that they do not loosen soils in areas that are prone to flooding. Fall tillage in flood prone areas is a sure recipe for significant soil loss to rivers and streams. However, cover crop establishment is often very poor when direct-seeding in mid- to late-fall because of cool soil temperatures and damage caused by slugs. What are the alternatives? A practical option sometimes attempted by growers is to interseed a cover crop in mid- to late-summer before the vegetable crop canopy becomes too tall or dense. Attempts to interseed cover crops had mixed results during the 90s in the Willamette Valley, but that was primarily caused by poor seed-to-soil contact when cover crop seed was broadcast over the top of the crop by plane or fertilizer spreader. Seeds lodged in corn whorls were consumed by rodents and birds or drifted with irrigation water into puddles. Another option is to use high clearance cover crop interseeders that drill cover crops into established sweet corn (at V6 or later) or other vegetable crops. One such planter developed by Interseeder Technologies (www.interseedertech.com) also side-dresses N fertilizer and applies post-emergence herbicides at the same time the cover crop is drilled. Cover crop interseeding with a high clearance drill will be the focus of this project and is not a new concept, but novel in this setting because: it addresses the challenge of cover crop establishment in soils near salmon-bearing streams and rivers where late fall tillage or soil disturbance of any kind can greatly increase potential soil loss in runoff; may reduce production expenses if fertilizer and herbicides can be applied at the same time as interseeding, and because it proposes a novel and integrated strategy to manage slugs damage with less pesticide.

1. Demonstrate the capability of interseeding with a high-clearance direct-seed planter to improve cover crop establishment and growth compared to conventional tillage or direct-seeding of cover crops after vegetable crops are harvested.

2. Determine the appropriate species and optimum time to interseed cover crops chosen by each farm-cooperator so that cover crop biomass is maximized, yet the cover crop does not reduce vegetable crop yield.

3. Collectively develop our cover crop knowledge and expertise so that the project team can effectively disseminate new knowledge.