Compost Application Rules

Rod Tyler

The U.S. Composting Council, Amherst, Ohio, has long-established rules of thumb for application rates using compost in various markets. These have commonly been reported to be good, dependable application rates in the field, and since the advent of new application equipment, more compost is being applied each year using these rules of thumb.

Some tips, from the book, “Winning the Organics Game — The Compost Marketers Handbook,” include:

Topdressing turf (existing lawns): Typically, it is recommended that turf is aerated prior to compost applications. Aeration involves creating small holes in the turf using a coring device, which removes a small core of soil and leaves it on the surface. After compost is applied at a rate of ¼ to ½-inch, the surface is raked, the cores break up and are mixed by the raking action with the compost, and the mixture falls into the holes created during aeration.

The benefit is that the organic matter of the soil changes because of the newly added compost. For turf, applying topdressing annually is recommended, and many professional companies are beginning to replace at least one application of fertilizer with one application of compost topdressing to stretch seasonal budget dollars.

New lawns: Compost applied at 1- to 2-inch depths and tilled into a 5-inch depth typically amends native soils and allows new turf seeding projects to be “jump-started” with a wide range of nutrients available from the compost and a good moisture reserve. As equipment innovators continue to work on new gadgets, they also see various new areas for application that may replace traditional methods.

“When we build a new home, there is a significant amount of effort spent on the final grading portion of finishing the yard,” says Bill Stinson, a builder in Richmond who runs Virginia's largest composting program. “We think the application of 1 to 2 inches of compost with a blower truck will give us a good, even surface for seeding, but we also think it will replace an expensive portion of the manual re-grading that we always used to do.”

Besides cost savings or even replacing the final grading cost with compost applications, Stinson says compost offers other benefits to Virginia's poor soils.

“Getting the organic matter into the soil prior to seeding or sodding is key, because once the turf is up and growing, your options to add organic matter really are limited,” he says.

Indeed, the poorer the soil conditions, the more compost is needed to add significant organic matter to disturbed soils. Many soils on the lawn or around the house actually are subsoils that result from the excavation for basements or overall site grading. These subsoils are not ideal for growing, and if organic matter is not added, using topdressing after aeration only will help the top few inches. If this is the case, roots will not be encouraged to go below the aeration depth and will depend more on irrigation and fertilization for proper growth.

Planting beds: Thirty percent by volume of soils used for planting beds should contain compost. Many companies now deliver blended soils, but in cases where this is not available or where there is abundant topsoil onsite, adding compost and blending it into site soils works well. Typically, a 2-inch application works best for planting beds. Remember, this is the last time the soil has a chance to be permanently altered by adding compost.

Blower trucks are useful in this application because when building construction is completed, it often is difficult for other equipment to get in.

“We can reach up to 300 feet with our hoses, and we can get through any gate or over the top of many fences,” says Robert Urbine, vice president of East Coast Wood Recycling Inc., Richmond, Va. “By the time you figure labor on getting to some of these places with wheelbarrows and small trailers, we already are done and on our next job.”

The trucks also are able to blow soils for application. Many of these trucks currently are used on projects where soils need to be placed into rooftop garden areas, hospital parking areas or other high-rise buildings. Rooftop mixes generally are lighter than normal soils, but the trucks are capable of installing a blended soil mix directly into landscape beds as well, eliminating several steps.

Landscape plant mulching: Because of its dark color and soil-amending properties, using compost for mulch is becoming more common. For companies using a large number of annual and perennial plantings, compost mulch provides a natural amendment that may be worked in around plants once they cycle through the growth process each year.

“The blower trucks also give us an added advantage in the planted landscape,” Urbine says. “We can quickly get between established plants without any damage, and the application actually uses less material compared to putting the mulch down by hand.”

Although you may hear about local markets only using hardwood bark mulch, look for a compost/hardwood blend to soon take over the market because it uses the beneficial properties of both materials in one convenient blend.