Can I plant garlic in raised beds that have contained red clover?
Question:
If I have planted red clover in raised beds that I won’t be planting into this growing season – as part of a rotation strategy – can I use one of those beds in Oct to plant my garlic into? How much nitrogen will the red clover have fixed in six months? How would I best and most easily terminate the red clover and how long should I plan on doing that before I plant my garlic?
Answer:
As you may know (since you’ve selected it), red clover is an excellent green manure/cover crop in the home garden, fixing nitrogen in the soil and providing organic material to improve the texture.
UMaine Extension Cover Cropping page
Sustainable Agriculture Research and Education (SARE) page on red clover
Because red clover is a perennial, it is usually left to overwinter for a season, or even two, for maximum nitrogen addition to the soil (you can see in-depth research on this in the SARE link above). But however long it’s in your garden, it’s a beneficial green manure for the soil.
I agree with your plan to terminate the crop before planting your clover, as you don’t want it competing with your sprouting garlic next spring. In the garden, as mentioned in the UMaine link above, this is typically done by physical incorporation–that is, turning it into the soil using a hoe and/or garden fork, and making sure it’s nicely chopped up and evenly spread about to decompose in your garden bed. There isn’t any reason why you can’t wait until very close to garlic planting to do so, in order to maximize the amount of nitrogen fixed. As noted in this UNH Extension page on growing garlic, garlic likes rich, well drained soil with plenty of organic material, so the incorporated green manure will be perfect.
As for how much nitrogen is fixed, I can’t give you exact figures on that (and was unable to find any studies on single season use of clover and resulting N totals from soil testing), but it will be more than when you started, and you’ll also get the additional benefit of improved soil texture.
>One final note: if you see the clover beginning to bloom, consider cutting it back a bit. It won’t kill the crop, and if it sets seed, you’ll have clover growing in your garden bed for a few seasons to come.