Use solar panel since tractor's generator not working?

I have to use a 12 volt battery in a farmall h with a 6 volt starter, so its generator can't charge the battery. I don't want to fix it properly. I also don't have hydro on my farm. Can I buy a cheap solar panel under $200 to charge this up? I may be using the tractor all day day after day for a while. Would this solar panel do :http://www.princessauto.com/all-seasons/outdoor/green-products/renewable-energy/8125155-15w-amorphous-solar-panel-with-7a-charge-controller It says 15 watt amorphous solar panel with 7A charge controller. Would this charge my battery back up in a few hours? Can I put it on the tractor as I go? I live in a sunny area.