The Impact of Planting Date and Seeding Rate on Forage Radish Productivity in Vermont.

Farmers are interested in growing forage radish (Raphanus sativus L. 'Diachon') as a cover crop since it offers multiple soil benefits. However optimum planting dates and seeding rates have not been established for growing these cover crops in Vermont. In 2016, a trial was conducted in Alburgh, Vermont to evaluate the impact of four planting dates (18-August, 24-August, 31-August, and 8-September) and three seeding rates (3.36, 6.73 and 13.45 kg ha^-1) on forage radish biomass production and nitrogen (N) uptake. The August planting dates did not differ significantly in total (root and shoot) dry matter biomass and produced an average 2,126 kg ha^-1. Root dry matter biomass was significantly higher for the 18-August planting date compared to all other planting dates. Vegetative shoot biomass was significantly highest in the 24-August and 31-August planting dates. Nitrogen removal rates averaged 44.0 kg ha-1 for the August planting dates and only 24.6 kg ha^-1 for the September planting dates. The 13.45 kg ha^-1 seeding rate produced on average 336 more kg ha^-1 of total dry matter biomass than the lower seeding rates. This trial suggests that planting forage radishes before the end of August improves biomass yield, nitrogen retention, and soil cover compared to planting by mid-September. At sites where erosion is a major concern or when planted later in the season, it may be advisable to use higher seeding rates to achieve optimum soil cover and biomass production.