My experiences could be vastly different to what you encounter in your area, deer density, surrounding food sources, climate etc. So take this into account.
The deer in my area are not particularly crazy about brassicas. I grow them mainly to provide variety and as a reliable heavy producing winter food source. So a 1/4 acre will last here usually all winter, and occasionally some will go to waste.
To get the maximum production several things have to happen.
- Proper planting time...Mid July-no later than 1st week of Aug.
- Optimum soil PH...6.5-6.8
- Lots of fertilizer...60-90#s 0f actual nitrogen. (150-200#s urea)
- Moisture...Too much rain, not enough rain....
- Seeding rate..4-6#s of seed per acre. (try not to over seed, its tricky)
A much more preferred plot for these deer is a mix of Winter Rye, Oats and Austrian Winter Peas. The winter rye in particular can stand up to heavy grazing and stays attractive all winter.
I generally plant 60-70#s of Winter rye, 90-100#s Oats and 50#s +/- Austrian Peas in a mix around Labor Day or a little later.
This plot is right beside a 16 acre cornfield, which is being used, but no where as much as this 2 acre plot.
The deer are using the brassicas/turnips some.
Some fairly large bulbs, despite lack of rainfall when it was really needed.