Green grounds care strategy: Maximize the mulch

By Cathy Walker  

Green Grounds Care Strategy: Maximize the Mulch

Landscape and grounds management is an original green industry, so it only makes sense that grounds managers should be in the forefront of adopting environmentally sound management practices. One of the easiest ways to begin is by leaving the grass clippings on the lawn. Mulching, or grass recycling, is an ecologically and financially responsible course of action.

Freshness Counts

Bagging and disposing of lawn clippings has been an accepted practice for years. But most grounds managers are finding alternate ways to achieve great looking lawns without the added time and expense of collecting and hauling clippings, not to mention the hassle of finding a dump site or composting. Many states and municipalities have laws forbidding yard waste, including grass clippings, in landfills. Many of these laws went into effect in the early 1990s.

Leaving clippings on the lawn not only saves time and the aggravation associated with bagging. Allowing the clippings to naturally decompose on the lawn also is healthier for the grass. Leaf blades are mostly water and decompose quickly, and the nutrients in the grass blades return to the soil and are available to the plants again. Some organizations have shown that they could reduce their fertilizer needs by 25 percent or more by mulching.

“One ton of fresh clippings contain approximately 15 pounds of nitrogen, 2 pounds of phosphorous, and 10 pounds of potassium — the three major nutrients — and smaller quantities of the other elements essential for plant life,” says Dr. Norman Hummel Jr., turf grass specialist at Cornell University.

By using less fertilizer, managers will more money in the budget and more time in the schedule for other activities. Reducing chemical use is another goal of green management.

Decomposed grass clippings also become organic matter in the soil and encourage earthworms and other beneficial microbial activity found in a naturally healthy soil, and healthy soil is the foundation of a lawn.

It is a myth that grass clippings contribute to thatch. Thatch — which is medium to dark brown in color and looks like a tangled, woven mat similar in appearance to sphagnum peat moss — is made up of dead roots and stems comprised of a waxy substance, lignin. Thatch accumulates when roots and stems are produced and die faster than they can decompose. Excessive fertilizer and irrigation contribute to thatch buildup.

Some grasses naturally produce more thatch than others. Kentucky bluegrass, zoysia grass, creeping bent grass and creeping red fescue, for example, produce more thatch than clumping grasses, such as tall fescue and perennial rye grass.

Equipment Issues

Managers do not have to compromise the appearance of the lawn when leaving the clippings. Proper mowing height and cutting frequency, combined with the right equipment, can result in a high-quality appearance every time.

A mower that is in good working order and has a sharp blade can be used for mulching. Mulching mowers and special blades can help, but managers first should pay attention to mowing height and frequency.

As a rule, equipment operators should mow regularly and remove no more than one-third of the grass blade at any one cutting. At some times of the year, this practice might require more than weekly mowing. Due to budgets, manpower, schedules or weather, this often is not possible, and that is when mulching equipment can help.

Workers should avoid letting the grass get very tall, then cutting it very short. Such irregular mowing will result in stress and unsightly clippings that can damage the lawn. They also should mow when the lawn is dry because dry leaves will dissipate more readily. Wet grass might clump on the lawn and under the mowing deck, making a mess in both places.

Occasionally, due to rainy weather or scheduling problems, grass might get too tall. If this happens, operators can raise the mowing deck for the initial cut, then lower it for a second cut.

If time allows for only one mowing, cut to the proper height and use a blower to disperse clippings evenly over the lawn. If possible, wait a day or two for the clippings to dry and shrink, then mow again. The second mowing will distribute the dry clippings so they are not noticeable.

Mowing frequency tends to depend on temperature, rain, fertilizer and the natural growth rate of the grass, but workers should do their best to maintain a regular schedule to maintain the desired height without removing too much grass at one time.

Mulch Matters

Numerous technological advances in mowers — specifically, mulching decks and blades — have increased the popularity of grass recycling among managers who traditionally have been most concerned about achieving a high-quality, polished appearance from their mowing operations. They now can meet these high standards with mulching mowers.

A mulching mower is designed to keep the grass blades suspended under the deck just long enough for them to be cut several times by the blades before the small particles are forced into the lawn, not dropped on top.

Managers must beware, though. Some decks claim to mulch but do nothing more than close off the discharge chute. With this type of deck, the clippings are just moved from one side of the deck to the other and can’t escape. This process results in a drain on the power, reducing the mower’s torque and effectiveness, as well as unsightly windrows or clumps. The deck might even stall when grass is wet and heavy.

New technology has provided more powerful mowers and new deck designs, allowing even larger mowers to become mulching equipment. Power and they way grass is handled under the deck are both important to mulch efficiently and meet appearance expectations.

As a rule, mowers with more horsepower are better suited to mulching. Their output of clippings is more acceptable, and they will not bog down as much in tall, heavy, wet grass that is common in early spring. Even with the higher horsepower, at certain times of the year, double-cutting might be necessary to achieve the desired results. But double-cutting still is faster than collecting and hauling clippings or raking clumps.

Each manufacturer has its own version of a mulching deck, but basically well-designed decks house aerodynamic baffles and blades that create airflow patterns to circulate grass clippings for repeated cutting and even dispersal.

Some newer decks are deeper — up to 51/2 inches — to allow more room for clippings and air to circulate under the deck.

Some newer mower models also have adjustable baffles that operators can open easily to conserve power and gain speed or close to create micro-sized particles. One manufacturer has designed a mower deck that can convert from a side-discharge unit to mulching deck with the pull of a lever.

Mulching mowers force clippings below the surface of the lawn, and this feature reduces the time needed to blow clippings from walks and drives and out of landscape beds. And since clippings or other objects are not thrown from mulching decks, make they are safer to operate around buildings, cars and pedestrians. Mulching blades are available to fit most mowers. These blades might have angled, notched teeth that lift and pulverize the grass blades, while others have multiple cutting surfaces.

Mulching blades also make it more practical to leave mulched leaves on turf. Light to moderate amounts of leaves will not harm mature turf, so there is no need to bag leaf debris when mulched in place. If leaf accumulations are heavy, chopping them into small particles with the mulching mower before bagging saves time, as more leaves can fit into the hopper and truck. Finely chopped leaves also will decompose in the compost pile faster.

How High is Too High?

Mowing height is important to ensure the appearance and long-term aesthetic value and health of grass. Follow these guidelines on optimal mowing height:

Bermuda grass
Less than 1 inch

Centipede grass
1 inch

St. Augustine grass
3 - 4 inches

Bahia grass
3 - 4 inches

Zoysia grass
Less than 1-1/2 inches

Tall fescue
2-1/2 - 3-1/2 inches

Kentucky bluegrass
2-1/2 - 3 inches

Perennial Rye grass
2-1/2 - 3 inches

Fine fescue
2 - 3 inches

— Cathy Walker

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  posted on 10/1/2007   Article Use Policy

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