I bought a cheap moisture meter online for around $20. The reason I ask is that the 1st 2 board bows I tried to make ended up breaking on me. Turns out they had too low of moisture content, around 7% (poor tiller and low moisture content = snap).
The stave that has dried for a year should be dry enough to make a bow, but I would want to check to be sure. You want to be between 9% and 12% MC. I would say 10% or 11% in our humid climate. Above 12% and it will take excessive set, and below 9% it will be brittle.
There are other ways to check moisture content that don't involve buying a moisture meter, but I haven't tried them.