On a typical highway or large earth moving construction project, the earthwork normally begins with having the ground surface scraped, picked up and placed where an embankment is needed. Whenever possible, projects are designed to be balanced to reduce the need to dispose of earth or to import fill material. Rarely is topsoil saved and. reapplied, even though research has demonstrated the benefits of that practice. What we are left to grow vegetation in--either for erosion control, revegetation or landscaping?EUR" is parent material. This material that has never been exposed to air or sunlight has little, if any, nutrient value. In this we are supposed to provide a long-term, vegetative cover? It is relatively easy to grow vegetation on subsoil. We have been doing so for years under the guise of erosion control. Most Landscape Architects are familiar with potting soils?EUR" sand, peat or nitrified bark- that nurseries use in place of soil. If we can supply seed, nutrient and water, we can grow vegetation on almost anything (what else is hydroseeding?). Quick, economical annual grasses are often recommended for erosion control because they can be established on non-fertile soils (and they make good cow food!) With enough fertilizer, water and appropriate climate, a vegetative cover can be maintained. In most erosion control applications, fertilizer is applied at the same time as the seed. Unless there is a mandated, vegetated density requirement, supplementary fertilization is rarely applied, and often over-applied, to assure adequate nutrient. Most chemical fertilizers are available whenever there is sufficient moisture, regardless of the plant's demand. Excessive moisture can leach away much of that nutrient. If temperatures are sufficient for plant growth, the plants will utilize much of that nutrient and hold it within the plant tissues. But if there are no microbes in the soil to decompose that vegetation and make the nutrients available again, it is lost as the litter is removed. The result is often an invasion of weeds. Weeds play a very useful role, as they often survive on little water and nutrient, and are not dependent on mychorrizae or other soil life forms. Weeds cover the ground, prevent erosion and start the process of soil formation. We could easily rely on advantageous species for our erosion control if we are willing to be patient for a few thousand years for the desired vegetation! As mentioned above, grasses are most often specified for erosion control because of the quickness of cover and availability of low cost seed; we suspect it is also because much of our knowledge of erosion control originated from the dust bowl attempting to stabilize and make productive ground desertified by agricultural practices. (This is why we grow cow food for erosion control.) However, in wildland erosion control?EUR" or where we are not willing to provide perpetual maintenance?EUR" we should endeavor to plant what will succeed in the local climate. Timber land grasses, chaparral or coastal sage scrub will delay or prevent the native species from becoming re-established. In many undisturbed wildland sites, invading annual grasses threaten the persistence of the native vegetation. The recent passage of AB 939 in California requires a fifty percent reduction of materials going to landfills by the year 2000. One of the easier materials to divert is the organic Component, as composting reduces the volume of material in half. The finished product should also have both horticultural and agricultural value, and provide an investment return. Many municipal and private landfill operators are producing good quality compost and making it readily available in the market place. Caltrans constructed the Livingston Bypass, a new freeway section, through Merced County in central California, eliminating the last stop light on Route 99. About half of the project is a depressed section, with 2:1 cut side slopes about fifty feet in length. The excavated material was used to build embankments and overpasses. Most of the fills have 2:1 sideslopes, but some of the bridge abutments are as steep as 1 1/2:1. The soils- very sandy and highly credible- literally melt and How when exposed to water; even light rains cause severe rilling and gullying. The soils have very little organic content, nutrient or water holding capacity. Of course any topsoil that existed was the first material to be excavated/ and is preserved forever under the fill slopes. Part of this project had been constructed under another contract a few years previously to accommodate a rail line that ran through the site. Originally seeded with annual grasses and legumes, the slopes produced an effective vegetation at first, but eventually became sparse and weeds began invading as the chemical fertilizer was lost. We decided to try and correct some of the soil deficiencies by adding compost both before and with the erosion control applications. We knew the compost would provide nutrients while increasing the organic content, water holding capacity and cation exchange capacity. We also thought that as the microbes further consumed the organics, they would exude materials that would help bind the soil particles together to form larger soil aggregates that would be more resistant to erosion. We used three erosion control application methods on this project. Each of these rely on straw?EUR" the most efficient and economical material we use- as the principal erosion deterrent material. The first treatment type, generally used on embankment slopes, requires the incorporation, or punching in, of straw with a Caltrans-specified roller. On cut slopes and other exposed areas, we rely on tacked straw. Seed is generally applied with a minimum of 500 pounds of fiber, used to cushion the seed through the hydraulic gears of the hydroseeder and to visually help the applicator spread the seed evenly. This is followed by an third application of an organic tackifier, generally psyllium or a starch based tackifier. Psyllium is the seed husk of the Plantago ovata plant. (Some of you may be more familiar with the medicinal form: Metamucil.) The third erosion control type used was drill seeding. This is the method most farmers use to seed their crops (ever see a farmer hydroseed on his crop?... hmmm). Drill seeding can be done on slopes 3:1 or flatter, by putting the seed into the ground and uses soil as the mulch. At a cost of about $400 per acre, this is one of the most cost-effective ways to plant seeds. And because the seeds placed in the ground where it is protected from predators and has a high probability of growing, the seeding rate can be reduced to about one-half that of hydroseeding. (When seed is applied by hydroseeding, there is as much seed exposed to the air as there is in contact with the soil. You don't get nearly the plant cover that you would with other seeding techniques, but you make lot of fat and happy birds) We don't yet know all the benefits of using compost in erosion control and revegetation projects, although there has been extensive work done with composts and organic inputs in agriculture and horticulture. On grossly disturbed sites with sub soils and parent material we think the benefits will even be greater. With the use of organic inputs, we may be able to "create" a viable topsoil. We do foresee that compost, especially in hydroseeding applications, will soon replace much of the fiber currently in use in the industry. It will provide a natural, slowly available and long-lasting nutrient supply for establishing native and ornamental vegetation--reducing pollution from nutrient runoff and leaching nitrates into the ground water. With all communities needing to reduce the materials going to landfill, it will make the production of erosion control materials local--rather than hauling over long distances--and will ultimately remove a resource from the waste stream to yield an extremely beneficial product. LASN