- This project is evaluating interseeding of crop crops to improve cover crop establishment after late harvested crops such as sweet corn and processing squash. In Project 1 at the OSU Vegetable Research Farm, 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 may have reduced corn yield slightly because of competition for water or nutrients. Applying Laudis herbicide immediately after interseeding of the cover crop had no impact on cover crop establishment, even when seeds were broadcast on the soil surface and incorporated lightly. Clover did not emerge well in interseeded plots, possibly because it was planted too deeply. Clover establishment was best when seed was broadcast on the soil surface and incorporated with shallow tillage. Cover crop biomass in mid-December averaged less in interseeded plots than in fall-planted plots because the oat cover crops began to senesce. In the on-farm demonstration plots (Project 2), triticale produced the most biomass and accumulated the most nitrogen in squash. Winter peas and oats had completely winter killed by mid-December. At a 2nd site in organic sweet corn, triticale and oats interseeded at V6 produced more cover crop biomass than lana vetch and clover at corn harvest. Sediment losses in runoff were slightly lower from plots with interseeded oats than from plots with corn residue on the surface and no cover crop. Project 3 demonstrated that increased seeding depth may help to avoid soil applied herbicide injury to small grain cereals and large seeded legumes, but that great seeding depths of red and crimson clover did not avoid vulnerability to herbicide injury.