This issue is the same one that the New Holland Boomers have. I was really hopeful that it had been fixed on the Farmall line.
The problem is that the acid splashes around inside the battery and gets forced out the vents as the battery off-gases. The battery CNH (Case New Holland) uses seems to be very prone to this problem. As long as the battery reads between 13 and 15 volts when the tractor is running, the charging system is probably okay and is not overcharging the battery.
The solution is to remove the battery, wash everything down with baking soda and water to neutralize any stray acid, and install a different battery. People have had good results with a sealed battery, gel cell battery, or spiral cell / paste battery. The best option is the last one. "Sealed" batteries actaully do have vents and can still leak acid. Gel cells are a fairly good option, but a spiral cell / paste battery, such as an Optima Battery, is the best. There are other brands, but the Optima website is here -
http://www.optimabatteries.com. Read the FAQ for some info. on them. You can buy them online from a few different web sites or get one from a local battery shop. My TC33D takes the model 51 Optima (you can use a model 51R by turning the battery around - it still fits fine). It was only available in a yellow top when I bought it, the red top may be available now (see the website for the difference).
If your tractor is under warrantee you can try to get the dealer to replace the OEM battery, but you will have the same problem all over again. I didn't want to watch my machine corrode away waiting for them to fix it.
Good Luck!