Topsoils with equal amounts of sand, silt and clay are often the best choice for most species of grasses. This loam topsoil can be achieved by adding certain growth-enhancing components such as compost, fertilizer or other additives to the soil before seeding. Established lawns can also be amended with these elements to promote healthy grass growth.
Loam topsoil provides three major benefits for grasses: it aids with air flow, helps retain nutrients in the soil and promotes proper drainage. The type of soil needed for healthy grass depends on the type of grass desired. Many varieties of grasses have specific nutritional needs that require maintenance unmet by topsoil alone.
Topsoil can be added to established lawns in thin layers so as to protect existing growth without blocking out sunlight or moisture. This top-dressing can prevent pooling water, which can damage the root systems of vegetation. Compacted topsoils can be aerated to promote better water and air flow in the soil, a common practice among lawn enthusiasts. Many soil-testing facilities offer services that break down the nutrients needed by a particular soil to promote healthy growth.
BriggsandStratton.com recommends amending the soil with the needed elements to promote healthy grass growth. Other factors involved in healthy grass growth include the soil's acidity or alkalinity, watering schedule, and adequate sunlight.