Herbaceous Wind Barriers (Feet)

603 - 1 NATURAL RESOURCES CONSERVATION SERVICE CONSERVATION PRACTICE STANDARD

HERBACEOUS WIND BARRIERS (Ft.)

CODE 603

DEFINITION Number of Rows. Barriers may consist of one row of plants, providing the required porosity can be Herbaceous vegetation established in rows or narrow achieved with a single row that contains no gaps and strips in the field across the prevailing wind the previous criteria is met. When two or more rows direction. are required to achieve the required porosity and to avoid gaps, the rows shall be spaced no more than 36 PURPOSE inches apart.  Reduce soil erosion from wind. Additional Criteria to Reduce Soil Erosion and/or  Reduce soil particulate emissions to the air. Particulate Generation from Wind  Protect growing crops from damage by wind Barrier Height. Barriers designed for this purpose or wind-borne soil particles shall have a minimum expected height of 1.5 feet during the wind erosion period for which the barriers  Enhance snow deposition to increase plant- are designed. available moisture. Barrier Porosity. Barriers established for this CONDITIONS WHERE PRACTICE APPLIES purpose shall be designed to achieve a porosity of 40- 50 percent. This practice applies to lands where crops or forages are grown. Barrier Direction and Spacing. The spacing between barriers shall be measured along the CRITERIA prevailing wind erosion direction during the critical wind erosion period (s) being planned for the field. General Criteria Applicable to All Purposes Spacing shall not exceed 10 times the expected Herbaceous barriers will be designed to reduce wind height of the barrier plus additional width permitted by the soil loss tolerance (T), or other planned soil velocities to meet purposes and resource objectives. loss objective. Calculations shall account for the Vegetation. Herbaceous wind barriers may be effects of other practices in the conservation system. composed of perennial or annual vegetation, living or dead. Plant materials shall be selected for the Additional Criteria to Protect Growing Crops from Damage from Wind or Wind-borne Soil following characteristics: Particles  Adaptation to local soil and climate During those periods when wind sensitive crops are conditions. susceptible to damage by wind and wind-borne soil  Stiff, erect non-spreading growth habit. particles, wind erosion shall not exceed the crop tolerance as specified in the National Agronomy  Resistance to lodging. Manual (Part 502), other accepted references or other  Good leaf retention. planned crop protection objectives. Assessments shall account for the effects of other practices in the  Tolerance to soil deposition resource management system.  Minimum competition with adjacent crops. Barrier Height. Barriers designed for this purpose Barrier Direction, Spacing and Composition. The shall have a minimum expected height of 0.5 feet barrier direction, spacing, and composition needed to during those periods when growing crops are achieve the desired purpose shall be designed using susceptible to damage by wind or wind-borne soil the currently approved wind erosion technology. particles. The designed height of the barrier will depend on the distance between the barrier and the

NRCS, NHCP January 2010 603 - 2 crop being protected. limits of the criteria above, to accommodate widths of farm equipment to minimize partial or incomplete Barrier Porosity. Barriers established for this passes. purpose shall be designed to achieve a porosity of 40- 50 percent during the period when growing crops are Selection of plants for use in barriers should favor to be protected. species or varieties tolerant to herbicides used on adjacent crops. Barrier Direction and Spacing. The spacing between barriers shall be measured along the Certain plants may be alternate hosts for pests that prevailing wind erosion direction during those may cause injury to adjacent crops and may not be periods when sensitive crops are susceptible to satisfactory for use in barriers. damage by wind and wind-borne soil particles. Consider plants that serve as a habitat for beneficial, Spacing shall not exceed 10 times the expected pest-eating insects or parasitizing insects, as well as height of the barrier plus additional width permitted pollinating insects. When enhancement of insect by the crop tolerance to damage from wind erosion as pollinator habitat is a secondary objective, diversity specified in the National Agronomy Manual (Part of flowering plant species should be encouraged. 502), applicable Field Office Technical Guides, other accepted technical references, or other planned crop Consider planning barriers to attract undesirable protection objective. insects away from crops. Calculations shall account for the effects of other Where compatible with the primary purposes of the practices in the resource management system. practice, priority should be given to plant species that will also provide food and cover for wildlife. The Additional Criteria to Enhance Snow Deposition selected species should be adapted to the site and to Increase Plant-Available Moisture meet the needs of the targeted wildlife species. Barrier Height. Barriers designed for this purpose In addition, when enhancement of wildlife habitat is shall have a minimum expected height of 1.5 feet a secondary objective, plant species diversity should during period of expected snow cover. Select be encouraged. Barriers that result in multiple vegetation to achieve appropriate barrier height to structural levels of vegetation within the barrier will manage snowdrift depth and length for manipulation maximize wildlife use. of snow storage. If the barrier is also designed to provide escape or Barrier Porosity. Barriers established for this nesting cover for wildlife, locate barriers where they purpose shall be designed to achieve a porosity of 60- connect areas of existing perennial vegetation 75 percent during periods of expected snow cover. whenever possible and include plants that will have a Select appropriate vegetation and density to provide minimum expected height that provides adequate needed barrier porosity to account for local cover for the targeted species. Barriers that connect conditions and desired snowdrift and depth. areas such as woody draws often provide additional Barrier Direction and Spacing. The effective escape and travel cover. Two or more rows are often spacing shall be measured along the prevailing wind more effective than one row, with a minimum width erosion direction during periods of expected snow of two feet between rows. Stiff stems are important cover. For uniform distribution of the drifting snow, in providing cover during severe winter storms. spacing shall not exceed 12 times the expected height Where damage to barriers by grazing animals is a of the barrier. concern, selection of plant species less palatable to animals may reduce damage. CONSIDERATIONS Where water erosion from melting snow, Transport of wind-borne sediment and sediment- accumulated within the barrier system, is a concern, borne contaminants offsite are reduced by this supporting erosion control practices such as residue practice when used in a resource management management can reduce the hazard. Where feasible, system. Consider need for other practices in aligning barriers across the slope can enhance combination with herbaceous wind barriers to meet moisture infiltration and reduce erosion from runoff. the resource objectives. Encourage the use of adapted native plant materials Herbaceous wind barriers are more suitable than field whenever possible. windbreaks for use under center pivot and linear move irrigation systems due to height considerations. Avoid use of invasive species. Windbreaks may be located outside the windward Consider using species of plants that sequester more edge of the system. carbon and/or increasing the width of the herbaceous Spacing between barriers may be adjusted, within the barrier to improve carbon sequestration. NRCS, NHCP January 2010 603 - 3 Consider barriers to enhance the micro-environment planting at recommended dates, leaving rows for plant growth. standing and maintained throughout the critical period for which the barrier was designed. PLANS AND SPECIFICATIONS Gaps in perennial barriers shall be replanted as soon Plans and specifications for the establishment and as practical to maintain barrier effectiveness. maintenance of this practice shall include: After establishment, perennial barriers shall be 1. Purpose fertilized as needed. Weeds shall be controlled by cultivation, spot treatment when using chemicals, or 2. For individual barriers other acceptable methods. a. Vegetation type (annual or Wind-borne sediment accumulated in barriers shall perennial) be removed and distributed over the surface of the b. Species field as needed. c. Number of rows per barrier Barriers shall be re-established or relocated as needed. d. Distance between barrier rows Barriers composed of perennial vegetation to also e. Seeding/planting rate enhance wildlife habitat should not be mowed unless f. Seeding/planting depth their height or width exceeds that required to achieve the barrier purpose, or they become competitive with g. Planned effective barrier height the adjoining land use. When mowing of vegetation h. Barrier width or prescribed burning is necessary, it should be done outside the primary nesting season for grass-nesting 3. For a barrier system birds. a. Number of barriers in system Harvest of hay or seed from perennial barriers, b. Distance between barriers grazing, burning, or mowing for weed control, shall be managed to allow regrowth to the planned height c. Total area in barriers before periods when wind erosion, crop damage, or d. Total amount of seed/number of drifting snow are expected to occur. Annual barriers plants required will be managed so barriers are of sufficient height and condition to meet their intended purpose. 4. Site preparation requirements 5. Method of seeding/establishment REFERENCES 6. Fertilizer and soil amendments needed Brandle, J.R., D.L. Hintz and J.W.Sturrock. 1988. Wind Break Technology. ISBN 0-444-43019-9. 7. Mulch material (if required) Elsevier Science CORE4 Conservation Practices – The Common Specifications shall be recorded using approved Sense Approach to Natural Resource Conservation. specification sheets, job sheets and narrative 1999. USDA, NRCS statements in the conservation plan, or other National Agronomy Manual. 190-V. 3rd ed., Part acceptable documentation. 502, Wind erosion. 2002. USDA, NRCS The plans shall include a sketch map or photograph Skidmore, E.L. and N.P. Woodruff. 1968. Wind of the field showing the approximate location of the Erosion Forces in the United States and their use in barriers. predicting soil loss. Agriculture Handbook 346. USDA OPERATION AND MAINTENANCE USDA-NRCS. PLANTS Database. 2010. Annual barriers shall be re-established each year by http://plants.usda.gov. (verified April 2010).

NRCS, NHCP January 2010