Cover Crop Chats: Brassicas

Amanda Rollins, September 3, 2020

 What kinds of brassicas can you plant right now? All of them for a few more weeks! (If you are wondering what in the world brassicas are, we have that answer for you HERE!)

       Now that we are into September, our time left for brassicas to have a great benefit in the Upper Midwest is coming to an end. Our usual “cut-off” date for seeding brassicas in a mix is around September 15th. After this point, there is not enough growing season left for the brassicas to develop enough to give you the full benefits that we are about to tell you about…

1. Deep Taproot

       The brassica we get the most questions about is the famous radish. We would almost say this is the most famous brassica because it is known for its deep taproot. The largest section of the radish tuber can reach up to 9-12 inches deep (or even deeper if planted early). This large root does help loosen soil in the immediate root area; however, for soil conditioning and compaction relief we prefer a grass with a fibrous root system mixed with the brassicas. What’s even more interesting is there is still a thinner section of the brassica taproot that can tunnel several feet into the ground to reach multiple layers sequestering many deep nutrients.

2. Nutrient Scavengers

       Speaking of capturing nutrients, all brassicas do a great job of this in the fall. Radish, turnips, rapeseed and others can readily take up available nitrogen, phosphorus, potassium, sulfur, magnesium and more/ These nutrients could otherwise be lost over the fall and winter until your next crop goes in during the following spring.

3. Nutrient Release

       Brassicas aren’t greedy. They release those sequestered nutrients back into the soil as they break down throughout the winter. Brassicas are not winter hardy and will not require spring termination to melt into the soil. The photos above are great examples of what brassicas look like growing in the fall vs. what they look like in the spring. A few holes in the ground here and there along with active soil biology where the brassicas were makes for great planting conditions. As you can see, there is very little residue left of the brassicas. That is why we always recommend brassicas in a mix with some kind of grass that will break down slower and provide some additional soil cover and erosion control.

What brassicas are you using in your cover crops this fall?