thinning alfalfa field. Should I interseed oats, barley or teff?

I have an alfalfa field that is getting thin due to number of years since planting. I would like to stretch out its life for another season and am considering interseeding. What results can I expect by planting oats, barley or teff? Last summer I planted teff in a field that had alfalfa previously and it was a great crop. Good sales and we now have customers who says they will buy every bale of teff I can produce. As you know, teff costs more than cereal grains, but I am more interested in the final result than the price of seed. Also, I do not know what rate to plant oats, barley or teff in the field to supplement it. Any advice is greatly appreciated.

thinning alfalfa field. Should I interseed oats, barley or teff?