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 often prevents cover crop establishment. One option to address these challenges is to interseed the cover crop mid-season into the vegetable crop. The goal of this project is to simply compare interseeding with traditional planting of cover crops. Cover crops have been interseeded with the assistance of cooperating producers on more than 80 acres of processed vegetable crops of sweet corn and processing squash over the first three years of the project in both conventional and organic systems, and performance of experimental plots compared to direct-seeded, conventionally planted, or fly-on cover crops. Field days have highlighted successes and limitations of interseeding strategies, and provided the context to develop future field tests.
- 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.
- 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.
This project now has 8 farmer cooperators. In discussion with growers, we developed research objectives relevant to their farming system. OSU provided the interseeding planter, planted the cover crops, and then monitored cover crop growth and development and estimated crop yield with small plot harvests and by processor weights, depending on acreage. Producers provided the seed and managed the plots agronomically in line with standard practices. Cover crops of oat, triticale, wheat, tall fescue, crimson clover, red clover, and common vetch were interseeded into sweet corn (organic and conventional), silage corn, and processing squash beginning in mid-June through mid-August.
Interseeded cover crops grew best in the less competitive crops such as squash and organic sweet corn. Interseeding preformed best in a late-planted field of organic sweet corn that was harvested in mid-October of 2015. The plot was located near the Willamette River and went under water several times during December and January. Interseeded plots withstood the flooding very well compared to adjacent plots that were direct-seeded (planted following corn harvest in October).
In 2016, the high clearance drill was again used to seed cover crop on approximately 25 acres in six row crop fields with five cooperators. Interseeding of a 4 way cover crop mix was contrasted with fly-on treatments in sweet corn and squash fields. Interseeding quadrupled cover crop stands compared to fly-on. Tall fescue and crimson clover established well enough in sweet corn that the grower wished that the entire 20 A field had been planted, rather than only half. The cover crop was planted immediately after a POST application of Laudis herbicide (without atrazine). Triticale interseeded into squash fields produced significant biomass in the fall, did not reduce crop yield, and helped to suppress weeds. Spring oats (Cayuse) established well in a conventional sweet corn field. An extremely wet October hampered growth of the cover crops and harvest of the vegetable crops. Two of the fields were bypassed by the cannery because of the wet conditions that caused more than 80% of the corn to lodge at one site. An entire squash field was bypassed because the harvest equipment continually became stuck. While these conditions prevented planting of comparison plots in the fall, the wet fall highlighted the utility of interseeding. Interseeded cover crops established and are still thriving, in contrast to vegetable fields where cover crop establishment was not possible because of very wet conditions that even prevented crop harvest.
In 2017, cover crops were interseeded on 7 farms in 9 demonstration trials on approximately 43 acres. For example, cereal rye, spring oats, and red clover were planted into organic squash following the last cultivation. Common vetch was seeded into organic sweet corn after the last cultivation. Tall fescue was planted into 33 acres of sweet corn following the success in 2016, but establishment was erratic and the grower chose to remove the cover crop in the fall before. Winter wheat was planted into conventional corn at V7 following corn harvest, and runoff collectors were placed in the field to measure sediment losses from inter-seeded plots compared to conventional and direct seeded cover crop plots.
The high clearance drill from InterSeeder Technologies has efficiently planted large seeded cover crops such as small grains and common vetch. We have had less success planting red and crimson clover. Drilling is very effective where moisture is short, but sometimes buries clover seed too deep causing very poor stands. Inter-seeding tall fescue (for seed production) into V6 or V7 sweet corn has garnered the most attention from producers, but we have only been successful in one of two years. This system has the potential of not only providing soil coverage during the fall, but also shortening the tall fescue establishment cycle by one season, which would greatly improve profitability in a processed vegetable/sweet corn system that is suffering economically. We will continue to develop the sweet corn-tall fescue system in 2018.
Educational & Outreach Activities
Growers and ag professionals visited on-farm field sites in March and September of 2016 to view demonstration plots and discuss the potential of inter-seeding to improve cover cropping outcomes. Results were presented at Oregon Processed Vegetable Commission annual grower meeting and at the North Willamette Horticulture Society meetings in January 2015, 2016, and 2017. A newsletter article highlighted the project and results from the 2015-16 cover crop season, and a poster was presented at the Within Our Reach conference in December 2016. The project was presented at the ASHS meetings in September 2017. A field tour of successful sites is planned for March of 2018. In development are a video clip showcasing operation of the inter-seeder, and a short extension publication on cover crop interseeding strategies in summer vegetable production.
The original team of producers has expanded to eight with on-farm demonstration plots again planned for 2017-18. The main outcome from 2015 and 2016 is that several producers will plant fescue in their corn as a method of establishing this crop during the summer, to shorten the seed production cycle. Relay planting is also being considered for seed crops such as triticale.
One cooperating farmer texted us this note following the 2nd year of the project. ‘I really want to thank you for reaching out to me for your project in the first place. Other than the fact that I love my job, it’s this type of stuff (referring to his successful establishment of tall fescue in corn) that keeps me interested’.