Compost For Turfgrass Establishment

Over the past few years, popular uses for compost in the landscape market have manifested themselves in categories such as turfgrass establishment, bed preparation, backfill for trees, topdressing, and mulch. Compost used as a general soil amendment for turf establishment can improve poor urban soil situations found in common landscape projects.

The driving force behind having a well-manicured turf is the general public, due to its increasing demand for green aesthetics. In a Gallup survey, residents cited beautification, relaxation, increased value, and other positive reasons for maintaining attractive lawns (Chad-bourne, 1994).

Turf establishment with seed or sod using compost is an accepted practice across a wide range of markets. For instance, the same basic steps to establish turf using compost apply to landscapers, golf courses, grounds maintenance personnel, and the average homeowner. Rule of thumb guidelines for using compost in most soils is a 1-inch application of compost (evenly applied) and tilled to a depth of 5 inches, achieving an approximate 20 percent inclusion rate by volume. A 2-inch application rate, tilled to a depth of 8 inches, has also been widely accepted, especially in sandy or clay soils. However, many rototillers only reach about 5 inches into the soil, limiting the amount of compost needed. A light dusting of compost as a final cover over seeded lawns helps to increase germination and reduces the need for applications of straw as a mulch.

When soil is found to be low in organic matter content and nutrition, highly compacted, or lacking water-holding capacity, compost is excellent to use as an amendment. The addition of compost improves the soil both physically and chemically, allowing for healthy growth of turf and ornamentals (Alexander and Tyler, 1992). Research has shown that the application of sludge compost at a rate of 260 metric tons per hectare (approximately 235 cubic yards/acre) enhances the establishment of turfgrass from seed (Alexander and Tyler, 1992). The application of 180 metric tons per hectare (approximately 160 cubic yards/acre) of compost was adequate for the establishment of turfgrass sod. In both experiments, compost significantly improved the rate of establishment and general appearance of the turfgrass (Alexander and Tyler, 1992, after Angle, 1981). The amount of compost or organic matter that has to be added to soil to in-crease the final organic matter content is deceiving. Because compost is usually lighter than soil, the contribution of organic matter (by weight) may not be as significant as adding another soil that is higher in organic matter content.

Contractors will note an increasing amount of compost required as the bulk density of each soil increases. Sand is heavier than clay, and requires more total organic matter to create the same increase in organic matter of the mix.

Compost used as a soil amendment for turf establishment should be rich in organic matter (more than 50 percent), free of weed seeds, and possess a texture and moisture content that allows for easy spreading (Alexander and Tyler, 1992). Compost with moisture less than 20 percent may make applications dusty, while moisture contents higher than 50 percent may be difficult to screen or apply with appropriate equipment. The pH and soluble salt content of the compost depends on the characteristics of the soil being amended and the plant materials being established. Generally, a pH of 6 to 8 and soluble salts of 5 mmhos/cm or less is considered safe enough for most turf (Alexander and Tyler, 1992).

This excerpt is reprinted from Winning the Organics Game, by Rod Tyler, published by ASHS Press (703/836-4606).