5 year old buck +
What are your opinions on planting buckwheat in my fruit trees and nut trees. Iwould rather do that than spray.
Unfortunately, even though flowering buckwheat will have the area full of pollinators, your mast trees will have needed that activity long before the BW begins to flower.
Yes it is weed suppression.
Would rye control the weeds?

I had clover around my trees, now it is quack grass.

Jerry-what kind of apples do you have in the ground?
Rye would control weeds as well as anything, and would last longer than BW. That buckwheat will die after 75-90 days. It will fall over and you would have nothing growing in your plot. I know some don't have luck with clovers, but a good hardy perennial clover patch is the most beneficial planting you could have in an orchard, IMHO. Try to establish a plot of a long term perennial white clover such as Durana or even Kura clover. You can control any encroaching grasses in the clover with cleth if you catch them when they are young, mowing the clover should control most broadleafs. It is hard to find any other method as long term or effective. Of the guys I help with land work, this is what they all have under and around their fruit trees. If you have a "problem child" pop up, just take care of them by spot spraying with an appropriate herbicide.