Legumes and small grains and some root crops.
Legumes... I think
@Heirloom farmer1969 from your area uses a lot of white clover. It is really good. Crimson is also good and adds some color. Vetch and Austrian peas are two of my favorites along with alfalfa for cool season/winter.
Small grains...winter rye, Elbon rye, oats, buckwheat, wheat etc. are all good soil builders for cool season/winter.
Root crops...daikon radish is amazing sending roots way down and pulling up nutrients. Turnips are also great.
Here's where my spring potato and tomato crop is going to grow in this space which has all of the above.
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