2017 ASHS Annual Conference

Cover crop establishment for producers of sweet corn in western Oregon is challenging after harvest, particularly for late planted corn, or if fall rains begin early. One solution for farmers is to broadcast cover crop seed over the corn canopy early in the season. This method often produces poor or erratic stands of cover crop because of poor seed to soil contact and seed predation. Another option is to drill the cover crop between corn rows when the corn is between V4 and V8. The objective of this research was to contrast the effect of cover crop seeding strategy and an amended weed control program with direct-seeded or conventional establishment of cover crops. In 2015, a cover crop of oat and crimson clover produced the most cover crop biomass when interseeded at V4 compared to V6 and V8 plantings, but interseeding at V4 may have reduced corn yield slightly because the cover crop competed for water and nutrients. Applying tembotrione herbicide immediately after interseeding of the cover crop had no effect on cover crop establishment, even when seeds were broadcast on the soil surface and incorporated lightly. Clover establishment was best when seed was broadcast on the soil surface and incorporated with shallow tillage. In 2016, competition from white super sweet corn hampered cover crop growth after emergence, and extremely wet conditions in the fall suppressed drymatter accumulation to less than 25% of drymatter produced in 2015. Applying topramezone herbicide immediately after interseeding did not effect cover crop establishment. We noted in one on-farm trial that tembotrione severely injured red clover, and a separate study evaluated clover tolerance to tembotrione and topramezone applied during interseeding. Crimson clover was tolerant to all rates of tembotrione and only showed signs of injury at 4 times typical field rates. In contrast, red clover was killed by tembotrione at typical field rates. Topramezone injured red clover, but only at 4 times typical field rates. Interseeding cover crops into sweet corn is possible, but careful timing and selection of herbicide is needed if the practice is to be successful.