Definition
A filter strip is an area of grass or other permanent vegetation used to reduce sediment, organic particulates, nutrients, pesticides, and other contaminants from runoff and to maintain or improve water quality.
Purpose
Filter strips intercept undesirable contaminants from runoff before they enter a water body.They provide a buffer between contaminant source, such as crop fields and water bodies, such as streams and ponds.Filter strips slow the velocity of water, allowing the settling out of suspended soil particles, infiltration of runoff and soluble pollutants, adsorption of pollutants on soil and plant surfaces, and uptake of soluble pollutants by plants.
Secondary benefits:
- Habitat for wildlife and beneficial insects
- Watershed protection
- Aesthetics
- Protect riparian forest buffers from erosion and sediment
Where they are used:
- At the lower edge of crop fields or in conjunction with other conservation practices
- On fields along streams, ponds, lakes, wetlands and drainage ways
- As part of a riparian forest buffer system
- As part of an agricultural waste management system
- At the lower end of surface irrigated crop fields to trap sediment and sediment attached contaminants from furrow irrigation erosion
- As part of a cropland management system that includes improving or establishing wildlife habitat
Conservation management system
Filter strips are normally established as part of a conservation management system to address the soil, water, air, plant and animal needs and the owner's objectives.It is important on cropland to plan the conservation crop rotation, nutrient and pestmanagement, and other cropland practices.Filter strips can also provide forage production, wildlife habitat and improve farm aesthetics.They are most effective when used in combination with other agronomic or structural practices to provide conservation benefits.
Wildlife
Filter strips can enhance wildlife objectives depending on the vegetative species used and management practiced.Consider using native or adapted vegetative species that can provide food and cover for important wildlife.Delay mowing or grazing of a filter strip area until after the nesting season.
Specifications
Site-specific requirements are listed on the specification sheet.Additional provisions are entered on the job sketch sheet.Specifications are prepared in accordance with the NRCS Field Office Technical Guide.See practice standard Filter Strip (393).
Operation and maintenance:
- In areas with annual rainfall above 18 inches, mow (and harvest if possible) filter strip grasses frequently to encourage dense vegetative growth.For ground nesting wildlife, care should be taken to avoid mowing during nesting periods.
- Control undesirable weed species.
- Inspect and repair after storm events to fill in gullies, remove flow disrupting sediment accumulation, re-seed disturbed areas, and take measures to prevent concentrated flow in the filter strip.
- Lime and fertilize according to soil test recommendations.
- Exclude livestock and vehicular traffic from the filter strip during wet periods of the year since filter strips rely on infiltration for reducing contaminants.It is recommended that this type of traffic be excluded at all times to the extent that it is practical.
- Restoration is required once the filter strip has accumulated so much sediment that it is no longer effective.