An extra step by home builders could lead to better yards

The soil that surrounds new houses in most production-built communities in the Washington area is of such poor quality that foresters and turf specialists call it dead soil.

How is that possible?

Before home construction begins, builders remove the topsoil and stockpile it to the side. When the house is completed, the topsoil is put back.

That provides some boost to a new yard, though not nearly enough, because all that stripping, stockpiling and respreading is disruptive. The topsoil is not remotely the same quality as what was there before, said Vincent Verweij, an urban forester with Arlington County Parks and Recreation.

But the biggest factor in the problem, Verweij said, is what happens to the subsoil after the topsoil has been removed.

The builder is legally required to stabilize the subsoil to ensure the stability of the foundation, basement floor slab and walls and the grading around the house, and he does this by compaction, he said. But the compaction degrades the soil quality, increases its acidity, kills microbes and significantly reduces the ability of the tree roots and other roots to take hold and have access to nutrients.

Although necessary, the compaction creates a type of soil so firm that experts call it hardpan. Mike Goatley, a turf specialist at Virginia Tech, said that trying to landscape in a yard with this type of subsoil is like trying to grow plant materials in concrete.

There is a solution, which requires a builder to take an additional step.

Typically, at the end of the job, a home builder engages a landscaping contractor to scarify, or lightly till, the surface of the compacted subsoil before spreading the stockpiled topsoil. Then the yard is sprayed with a mixture of water, green paper mulch, seed and straw. (In late fall or early spring, sod might be used instead.) The extra step would require the landscaping contractor to spread a two-inch layer of new compost and thoroughly rototill it to a depth of 4 to 5 inches before the spraying. To be effective, a high-quality compost from a reputable source, such as a local municipalitys compost-producing facility, must be used.

Breaking up the uppermost layer of subsoil greatly increases the soils ability to absorb rainwater, and adding the top-grade compost gives a huge boost to everything planted in the new yard.

See the rest here:
An extra step by home builders could lead to better yards