The Department of Public Works specifies the use of rice straw mulch for protecting finished soil surfaces for its contractors and maintenance crews. Straw mulch protects the surface from the impact of rainfall, which can loosen soil particles and suspend them into runoff. Suspended sediments create turbid water, and are cited as one of the leading pollutants of San Mateo County streams. Mulch also protects newly seeded ground, allowing plants to establish and stabilize the soil.
Rice straw may contain small amounts of weed seed. Because rice is grown in still or slow-moving water, however, any weeds that may grow with rice are generally incompatible with the higher velocity streams in San Mateo County. Therefore, there is little risk of establishing non-native weeds through the use of rice straw in erosion control.
Rice straw is a by-product of California's large rice farming industry. Tons of rice straw are disposed of by burning it, contributing to air pollution in the Sacramento Valey. The State of California offers tax incentives for using rice straw in construction and erosion control products. To learn more, visit the California Department of Food and Agriculture's Rice Straw page.
Cereal grain straws such as oat, wheat and barley contain large amounts of seed. The introduction of cereal grain grasses may be acceptable in some cases, but should be avoided wherever the reestablishment of native plants is desired.
Forest litter (redwood duff, leaves, etc.) is often the best mulch. It contains large amounts of native plant seeds, lots of soil cover and all the right nutrients to get the native plants growing again.