Renfe madrid to merida. The new schedule is not out yet. Information on the last schedule for 17/01/2014. If you are coming from madrid barajas airport, you can buy ticket at the renfe station for madrid*-merida. You ticket will include the free commuter train (cercanias) to madrid atocha station where you will board your train for merida. As stated by laurie, the schedules will be more or less the same.
On this particular day, there are 4 trains departing for merida.
R express 17014 Dep 08.07. Arr 13.11. Duration. 5h 4 min Price 2nd cl. 30.25€
Intercity 17900. 10.18. 15.08. 4h. 50 min. 36.30
Md 99778. 14.32. 21.42. 7h 10 min. 41.20
Note: you have to transfer to another train, so i don't recommend it.
Intercity 17194. 16.19. 20.49. 4h 30 min. 36.30
I hope this helps. Buen camino