If you’re planting into good conditions then it doesn’t take much turnip seed at all. There’s a dang gazillion little turnip seeds in a pound. Most people probably bury them too deep in traditional plantings but they do outstanding in a properly done T&M planting. I only added 1 lb to the acre of turnips into my mix last year (pic below). In some places it came in even thicker but this is a pretty good representation of the average. My seed blending left a little to be desired. Radish seeds are just a little larger so you could up the rate a little on them compared to rape or turnips. It’s your call in the end as to how thick you want your brassica component. It doesn’t take much overdoing it to end up with just a brassica patch.