Utilization of compost as an erosion control tool is gaining momentum for many reasons. Compost offers excellent surface protection for reducing topsoil loss while providing a favorable substrate for hydroseed mixes. Soil moisture is retained and nutrients for vegetation are provided, meanwhile inhibiting undesirable plant species. However, there is wide variation in available compost sources and cost. Possible interactions between compost composition, soil type and vegetation production may occur. Hence, an experiment aimed to determine whether there is a noticeable difference in erosion control and seedling germination performance between several common types of compost applied at varying rates and methods over two subsoils was established.

The experiment was conducted at the Erosion Research Facility at California Polytechnic State University, San Luis Obispo, in conjunction with the California Department of Transportation, and the Office of Water Program at California State University, Sacramento. Fine sandy loam and silty clay subsoils were collected from two California highway construction sites. Test boxes were filled with one of the two soils, compacted, and positioned at a south-facing 2H:1V slope. After compost application, a hydroseed mix of four California native shrubs, Baccharis pilularis, Eriogonum fasciculatum, Eriophyllum confertiflorum, and Lotus scoparius, were seeded on the test boxes. Applications of the three composts included 1) topical 16 mm depth, 2) an admixture of soil and compost (25% by volume), as well as hydroseeding (finest textured compost only) at 3363 kg/ha with 1121 kg/ha fiber, 3) natural rainfall collected from boxes was analyzed for total water runoff, sediment load, sediment concentration, pH, total dissolved salts, and turbidity. In terms of water quality, all compost treatments performed significantly better than the control. Direct surface application consistently produced better water quality than mixed compost/soil application, yet mixing compost with the sandy clay loam produced more native shrubs.


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