Sorry about that, yes, I meant use a fertilizer high in Nitrogen. You may or may not need it depending on your soil, but brassicas like nitrogen, so in most cases it will only help. The problem is that if nitrogen isn't incorported into the soil by tillage or rain it will be lost to the atmosphere. Also, nitrogen can burn your plants if it doesan't get rained in. If you aren't sure of rain the next time you're up there, I'd just skip the fertilizer this year. Depending on how long your rye/clover had been there, they may have left behind enough nitrogen to please the brassicas.