Q. Your past few articles have covered the use of chemical pesticides and fertilizers for home lawns. I would rather not use chemicals if I don't have to. Are there any nonchemical alternatives for a healthy lawn?

A. The short answer is yes. An effective substitute for chemical fertilizers on the lawn is an occasional top dressing of compost.

Compost consists of decomposed plant material and is sometimes fortified with manure. Locally produced compost products are Menehune Magic and EKO. As the compost continues to decompose, it slowly releases low levels of most of the essential nutrients necessary for healthy plant growth. These minerals, including nitrogen, provide lasting results. The end product of the decomposition process is humus, that charcoal-like residue that greatly improves soils' nutrient-holding capacity.

A thin layer of compost — no more than a half-inch thick — can be applied over the lawn as a top dressing. It is best to mow the grass just before application. Use a broom rake to work it into the underlying thatch layer and then water well. The green tips of the grass should still be visible. When used in this manner, one cubic yard of compost will cover about 600 square feet of lawn. (An average pickup-truckload is about three-quarters of a cubic yard.) The greatest benefit of using a compost top dress on lawns is immediately after verticutting the thatch and/or core aeration of the soil.

The tradeoff is time and money. Chemical fertilizer was invented for convenience and bargain prices. If you use a chemical fertilizer on a 2,000-square-foot lawn, you would need to apply about eight pounds of a slow-release nitrogen formulation. This will cost about $5 and five or 10 minutes of your time.

Using compost will require three and one-half cubic yards (about four or five pickup loads) at a cost of about $100 ($200 if you buy the individual bags), and several hours to dump and spread the material.

Compost also can be used to enrich the soil under shrubs and trees. It can be spread in a thicker layer — one or two inches- and is best when it is mixed into the top three or four inches of soil.

Using mulch in nonturf areas is the best pesticide-free method to control weeds.

Mulch is different from compost and should not be used for that purpose. A good mulch is made up of larger dried pieces of wood chips or bark and is spread in a layer three inches thick under trees and shrubs to control weeds and conserve water. This wood mulching material should not be mixed into the soil because it will deplete the soil of nitrogen as it begins to decompose.

Chemical-free weed control of turf is a more difficult matter. In this case the best way to prevent weed infestation is to maintain a thick, healthy lawn. Provide adequate irrigation but don't over water. Top dress with compost once or twice a year, and mow frequently enough so that you remove no more than one third of the tops of the grass blades at each mowing. The mowing height should be toward the middle to upper end of the recommended height for your species of turf. Do not bag the clippings. Regular mowing also prevents weeds from getting a foothold.

Another nonpesticide weed control method is available if you have a seashore paspalum lawn. This turf has a very high salt tolerance and a saturated saltwater solution can be used to spot spray onto existing weeds. This will burn the weeds off with little damage to the lawn. After a few days irrigate the area well to flush out any salt buildup in the soil.

Jay Deputy is an education specialist in landscape horticulture and turf at the University of Hawai'i-Manoa, Department of Tropical Plant and Soil Sciences, and state administrator for the Certified Landscape Technician Program sponsored by the Landscape Industry Council of Hawaii. Got a lawncare or turf question? Write to deputy@hawaii.edu.