Just put the valve stem near the half way mark and release a bit of air. If your finger is wet, they are liquid filled. If not then not. Smell the liquid, if it smells sweet, then you've probably got Rim Guard in the tires. This is a good thing.
/ Power Required to Pull a Two-Bottom Moldboard Plow
Kubota Grand L 5740, loaded R1's w/640 lbs cast weight, 854 loader
You have the power but like others have asked, can you get that power to the ground? I pulled a two bottom 14 inch Ford 102 rollover plow with a Grand L3240 with 25 pto HP. Now I pull a three bottom oliver rollover with a Grand l5740 with 50 HP pto power. My soil is called sandy loam but it bears a striking resemblance to concrete when it is dry.