It is well known that confluence (which is equivalent to Church-Rosser property) is undecidable for arbitrary term rewriting systems. We prove here decidability of confluence for ground term rewriting systems. To obtain this result, we construct a special class of finite state tree transducers that we code in recognizable tree languages. Our work illustrates how tree language theory is useful in term rewriting systems study and we give easily some other results in the ground case (as decidability of uniform termination).