A mulching blade can help chop the clippings into smaller pieces, but the key here is whether your mower was designed as a mulching mower. Did it come with a mulching plug? If so, the original blade is a multi-purpose blade. As long as it's in good condition and sharp, it should be fine. It's also critical for the deck to be clean and kept that way for mulching performance.

If you don't want to buy a mulching kit you may want to try a pair of Gator Blades, they "mulch" with out a block off plate and are cheaper then OEM blades. I use mine with a block off plate just so I don't get grass clippings everywhere (city boy).

Evidently this thing is a rider. Try posting on the tractor/rider forum.