Mulching grass clippings back into the lawn is known as grass cycling. Most modern mowers have this feature. Rather than discharging the cuttings into a bag, the clippings are chopped again before falling harmlessly into your lawn. Even though the small clippings left behind are virtually invisible, they do promote the long-term health of your soil by adding additional organic material. Grass cycling can return as much as 30 percent of the nitrogen required by grasses for proper nutrition.
To be effective, grass-cycling is best done with a lawn mower that cuts, then chops the grass blades into the finer particles. This also requires more frequent mowing and removing less blade length with each mowing.
Do clippings returned to the lawn contribute to thatch problems?
Thatch is a layer of un decomposed or partially decomposed grass roots, stems, crowns, runners and lower shoots that accumulate between the soil surface and actively growing turf. Grass clippings contain 80 to 85 percent water and decompose much more quickly than other grass plant parts. Research indicates that clippings do not contribute to thatch buildup on any cool- or warm-season grasses, including zoysiagrass.
Before you start returning clippings to your lawn, make sure the thatch layer is no more than 1/2" thick. A layer more than 1/2" thick will prevent clippings from coming into contact with soil microorganisms. If thatch is a problem in your lawn, use a vertical lawn mower or power rake to reduce the thatch layer. Use the thatch as a mulch or add it to your compost pile.
Are mulching mowers any more effective than regular lawn mowers?
Mulching mowers are rotary mowers that cut clippings into smaller pieces and disperse them uniformly back into the lawn for decomposition. Removing only a third of the vertical green growth is very important when using a mulching type of mower. Well-designed mulching mowers distribute clippings more evenly across the lawn surface than regular lawn mowers.