Buckwheat's greatest quality is its ability to out-compete weeds. This quick-growing tender annual also builds organic matter.
For a fall crop, sow in late August/early September. Just make sure your crop does not set seed, as buckwheat can be weedy if allowed to self sow. As long as no seeds form, simply let the buckwheat winter kill, and incorporate in the spring if necessary.
Several successions of buckwheat can be grown during the season. For a summer cover crop, mow or cultivate at flowering to kill the plants.
Buckwheat flowers attract many beneficial pollinators in the summer as well, and can be used in pasture and field mixes.