Wednesday, November 15, 2006

Amendment of Yard Waste Compost to Roadway Slopes to Improve Sediment Control and Water Quality.

M.J. Curtis, D.E. Rider, and V.P. Claassen. Univ of California, Davis, 2135 Plant Env Sciences Bldg, Land Air and Water Resources, One Shields Ave, Davis, CA 95616-8625

This study was designed to evaluate the influence of compost application to sloped roadway embankments on sediment reduction and water quality.  In the fall of 2005, field plots were constructed on a loam soil with a 2:1 (run:rise), 50 % slope to monitor runoff and sediment/nutrient losses for each precipitation event during a storm season.  Nine treatments were tested: 1) consolidated (untilled) soil, 2) tilled, 3) annual grass, 4) screened and cured compost mulch over consolidated soil, 5) screened and cured compost mulch over tilled soil, 6) screened and cured compost tilled into soil, 7) screened and cured compost mulch over screened and cured compost tilled into soil, 8) unscreened uncured compost over consolidated soil and 9) screened and cured compost over consolidated soil with annual grass cover.  Runoff was collected and analyzed for sediment, total particulate carbon, total particulate nitrogen, total phosphorus, dissolved carbon, dissolved organic nitrogen and mineral nitrogen.  Preliminary results indicate that a compost mulch (made of screened and cured material) will generate nutrient losses that may impact nearby water resources.  Tillage-only treatments reduced runoff volumes and, when the screened and cured compost was tilled in the soil, far fewer nutrients were lost.  The lowest nutrient losses were from compost  (unscreened and uncured) applied as a surface mulch.  If the soil is lacking nutrients and a cured compost is needed, then it should be tilled into the soil to reduce nutrient losses.