Which grass/legumes species have shallow root systems?

I will plant peach trees in a deficit irrigation system in which I will also plant a mix of grass species underneath. I am hoping to exclude peach tree roots from the top soil layer and force them to grow in deeper soil layers by generating a water shortage due to competition with the associated grass/legumes species. I am therefore looking for a mix of grass/legumes species with shallow root systems (less than 50 cm) to create competition only in the upper part of the soil.