Subject: CP15B, Establishment of Permanent Vegetative Cover (Contour Grass Strips) on Terraces

Farm Service Agency Washington Notice CRP-372 for practice CP15B, Establishment of Permanent Vegetative Cover (Contour Grass Strips); On Terraces, dated August 30, 2000, provides conservation planners a new dimension in the establishment of resource management plans on cropland. The practice allows seeding grass on terraces that are beyond the life span of any state or federal program and that are still considered functional. This Continuous Conservation Reserve Program (CRP) practice offers land managers an incentive to implement a practice that will reduce water and wind erosion and improve water quality.

For CP15B to be utilized, the terrace system must be functional. Functional terraces are defined as having at least 50 percent of their designed capacity. If the terrace is determined to be non-functional, repairs must be made at the applicant's expense, by filling low areas and elevating the ridge, to be eligible for practice CP15B.

The CRP-372 notice allows seeding grass on the terrace, a 10-foot buffer above the cut slope of the terrace channel, and a 10-foot buffer below the end of the fill slope of the terrace ridge on broad-based terraces. It also allows seeding 10 feet above and below the terrace ridge on grassed back and narrow-based terraces. A minimum width should be used to solve the resource concern but the maximum width cannot exceed 60 feet.

Dense grass stands covering the entire channel will increase the needed flow depth by 50 percent. To eliminate the need to increase channel capacities, an increase in residue levels on the cropland between terraces is necessary. In high residue systems such as no-till and those systems with 50 percent surface cover, terraces may be seeded to the entire 60 feet. Establishing grass on only the ridge portion of the channel has no significant impact on the flow depth of the terrace. In low residue management systems, seeding should be limited to the front slope, back slope, and the 10-foot buffer below the end of the fill slope of the terrace ridge. Contour grass strips on terraces will be alternated with wider cultivated strips.

When planning the system, it is advisable to parallel the cropped land between the grassed terraces whenever possible. The maximum size standard allows for a 10-foot buffer above the channel cut slope and below the toe of the back slope. If the seeding covers only the ridge of the terrace, the 10-foot buffer would only apply below the toe of the back slope. The maximum would then be determined by adding the average width of the terrace ridge and the 10-foot buffer below the terrace ridge not to exceed 60 feet.

When terraces are established to grass, it naturally promotes contour farming, enhancing sheet and rill erosion control. This practice also eliminates gully and ephemeral erosion from concentrated flow that is associated with nonfunctional terrace systems.

Every terrace in the field does not have to be grassed under the provisions of this practice. The planner should try to include those areas of least production, of greatest erosion potential, and closest to water conduits. Not seeding each terrace will still promote contour farming, but the planner should be aware of terrace alignment and take advantage of the natural alignment to provide the best farming conditions possible when implementing this practice.

Improving the alignment of the system eliminates several turns and point rows and, in turn, reduces excess nutrient and pesticide applications. Benefits to water quality will be realized by reduced erosion, less nutrients applied, and less pesticides applied.

Another enhancement to the resource management system might be wind erosion control. The height of the grassed terrace adds greater protection to the downwind area than cross wind trap strips installed on level surfaces. The ridge elevates the grass planting and provides greater height to the barrier.

Seeding mixes consistent with Practice Standard and Specifications for Upland Wildlife Habitat (645) or Range Seeding (550) will be used to provide cover consistent with the desires of the land user. If areas of the terrace are presently in vegetative cover, those areas are not eligible. For fields where the sheet and rill erosion exceeds "T", it is suggested to use seeding mixes documented in Critical Area Planting (342) to increase survival and speed establishment on the more erosive areas.

Grassed terraces provide an area for wildlife and large numbers of predatory insects that enhance pest management without added cost to the producer. The area may also harbor pests that are potentially damaging to crops. Scouting for pests early provides the opportunity to use the grass strips as trap areas and treat problems prior to field infestations.

The attached CP15B Worksheet will be completed to document that CP15B practice requirements have been met. The worksheet will be provided to the Farm Service Agency County Committee and maintained in the producer case file.

The NRCS component practices for CP15B that may be used for reporting purposes are Contour Buffer Strips (332) and Cross Wind Trap Strips (589).

These practice codes may be reported in the Performance and Results Measurement System for all CP15B's when the practice standards (332 or 589c) are met. Do not report any acreage that was previously reported through the NRCS reporting system.

/s/

TOMAS M. DOMINGUEZ
State Conservationist

DIST: A, F, S, NPR, FSA (3), L. Frees-S. Hutchinson FO, Krueger, Davis, T. Conway, Schroeder (KDWP)

The following document requires Acrobat Reader.

Attachment (PDF; 60 KB)