Living mulch between rows of an orchard

I have put down a lot of wood chips on my new orchard over the summer.   It is 1/2 acre and surrounded by houses and woods and there is thick damp clay at 6 inches in most places.
~ Got a case of aspergillis in the lung so please wear a mask when working with old chips.~
The trees are all twigs now, but the land was previously heavily wooded so I know the soil is great.  
I expect the wood chips to be degraded in the spring and I want to put down something (broadcast) that will cover the ground and add some benefits to the soil.  I have a bunch of winter pea, mustard and 7 top turnip seeds that I will put around each tree (two feet away).  I like it when you can go collect some greens for dinner in some random location.
I want to put something in between the rows since surgery will happen in the spring and am trying to minimize future work.
Any recommendations on what to plant that will remain low height?
I know Dutch White clover is one idea I have been carrying around.   It grows well here and comes back every year.  May add some hairy vetch and some crimson clover.  
Anyone have any success with an alleyway cover that is perennial?

My clay field has persistent crimson clover more so than the white clover where it dries out during our dry summer.  Harry vetch and alfalfa are good where I mow for mulch.  I have an area viewed from the house that my wife wants to look lawn like. It dose very nice with a short lawn grass that after late spring mowing I allow to go to seed during the summer then mowed with the mulching blade keeps it re seeded. I mow the tall grass with a scythe in summer and mulch under the plum trees to catch the falling fruit.