The theoretical ideal is to rehabilitate a flawed landscape to the natural condition it was in before development, though realistically this is often not possible or even desirable. In addition, this convention requires topsoil to be removed from another site, thus contributing to its degradation. Less obvious altered landscapes also exist on residential sites where prevailing lawn and foundation planting are present. Furthermore, the indigenous landscape that might have originally existed on this land may have been displaced many years ago for agricultural fields. Many residential landscapes have been severely altered from their once natural state and are degraded environments, though they may not always appear that way. Though green and “landscaped,” such sites often suffer from poor soil, lack of plant diversity, minimal wildlife habitat, and a maintenance practice fed by chemical fertilizers and pesticides (Figure 3—8). In some instances, clay or sand can give the soil more desirable structure. One caution in using community compost is to determine what materials were used to produce it. Figure 3-9
Benefits of compost in restoring poor soil. The soil’s organic content and overall health can likewise be dramatically improved by adding compost. A sustainable landscape relies extensively on healthy soil to support all life in and above the ground, so it must be rejuvenated before other restoration strategies are applied. Calcium, gypsum, phosphorus, nitrogen, or other minerals might be added to affect fertility and pH. Some soil scientists recommend that compost be tilled
Common environmental problems of a degraded residential landscape. The most obvious impaired sites are the barren landscapes found around newly constructed homes in recently developed subdivisions. And compost-amended soil allows surface water to more effectively percolate down through the soil, thereby increasing soil moisture while reducing the quantity of runoff from a site (also see “Reduce Runoff” in this chapter). Adding compost is one of the most effective means of reviving poor and compacted soil. In addition, spoiled landscapes exist in older urban sites that have undergone years of poor management or neglect. And topsoil is often not necessary where native plants are used. Trucks and heavy equipment integral to such an operation require a proportionally large amount of fuel. Consequently, the challenge with many residential sites is not to preserve the existing natural setting, but rather to restore the site to an improved, flourishing state. The traditional practice of importing new topsoil to a site as a growing medium should be minimized if not avoided altogether. The damaged site can and should, however, be restored to a healthy, sustainable
МOІ Small $ і sola-fed hotorfcrts! into the soil to achieve a 2:1 ratio between existing soil and compost by loose volume. This can be translated to adding 2"—4" of compost for every 6"—8" depth of soil (Figure 3—9). This goal is best accomplished in two general phases. condition that is a viable place for people, flora, and fauna. First, all the problems and inappropriate materials found on the site must be corrected or removed, as discussed next. Second, the site must be redesigned based on sustainable principles presented throughout this chapter. The compost should also be “mature” so that it doesn’t deplete nitrogen from the soil to which it is added.