332 - 1

NATURAL RESOURCES CONSERVATION SERVICE

CONSERVATION PRACTICE STANDARD

CONTOUR BUFFER STRIPS

(Ac.)

CODE 332

DEFINITION

Narrow strips of permanent, herbaceous 

vegetative cover established around the hill 

slope, and alternated down the slope with 

wider cropped strips that are farmed on the 

contour.

PURPOSE

This practice is applied to support one or more 

of the following purposes:

• Reduce sheet and rill erosion. 

• Reduce water quality degradation from the 

transport of sediment and other waterborne contaminants downslope. 

• Improve soil moisture management 

through increased water infiltration. 

• Reduce water quality degradation from the 

transport of nutrients downslope. 

CONDITIONS WHERE PRACTICE APPLIES

This practice applies on all sloping cropland, 

including orchards, vineyards and nut crops. 

Where the width of the buffer strips will be 

equal to or exceed the width of the adjoining 

crop strips, the practice Stripcropping (code 

585) applies.

CRITERIA

General Criteria Applicable to All Purposes

Surface flow from contoured crop rows must 

be delivered to a stable outlet.

Design the width of the cropped strip to 

accommodate some multiple of full equipment 

width.

Do not plant buffer strips with any plants listed 

on the noxious weed list of the state.

Do not use buffer strips as travel lanes for 

livestock or equipment. 

Buffer strips are not a part of the normal crop 

rotation (however, they may be harvested or 

grazed), and will remain in place until they 

need to be renovated or re-established.

Row Grade. When the row grade of any crop 

strip reaches the maximum allowable design 

grade, establish a new baseline up or down 

slope from the last buffer strip for the layout of 

the next crop strip. 

Arrangement of Strips. A crop strip will 

occupy the area at the top of the hill, unless 

unusually complex topography requires 

vegetation in this area in order to establish a 

farmable system. 

When used in combination with terraces, 

diversions or water and sediment control 

basins, the layout of the buffer strips shall be 

coordinated with the grade and spacing of the 

other practices so that the buffer strip 

boundaries will parallel the practices as closely 

as possible. Locate the buffer strip 

immediately upslope from the terrace channel, 

or diversion, or the storage area of the water 

and sediment control basin.

Additional Criteria to Reduce Sheet and Rill 

Erosion

Minimum Row Grade. The cropped strips 

will have sufficient row grade to ensure that 

runoff water does not pond and cause 

unacceptable crop damage.

Maximum Row Grade. The maximum row 

grade will not exceed:

• One-half of the up-and-down hill slope 

percent used for conservation planning, UORU

2%, whichever is less. 

NRCS, NHCP

September 2014

Conservation practice standards are reviewed periodically and updated if needed. To obtain 

the current version of this standard, contact your Natural Resources Conservation Service 

State Office or visit the Field Office Technical Guide.
332 - 2

• Up to 3% row grade is allowed for a 

maximum of 150 feet as crop rows approach a 

stable outlet. 

Width of Strips. The minimum width will be

• At least 15 feet wide for strips planted to 

grasses or grass-legume/forbs mixtures

with at least 50% grass and 

• At least 30 feet wide when legumes/forbs

are used alone or legumes make up more 

than 50% of the stand.

Increase buffer strip widths as needed to keep 

the width of the cropped strips uniform. The 

width of the individual buffer strips may vary.

Cropped strips will be of uniform width 

between buffer strips and will not exceed 50% 

of the slope length (L), used for the erosion 

calculation.

Vegetation. Establish buffer strips to 

permanent vegetation consisting of grasses, 

legumes/forbs, or grass-legume/forb mixtures.

Establish species that are adapted to the site, 

and tolerant of the anticipated depth of 

sediment deposition. 

The buffer strips will have at least 95% ground 

cover during periods when erosion is expected 

to occur on the cropped strips.

The stem density for grasses and grasslegume/forb mixtures will be at least 50 stems 

per square foot, and for pure legume/forb 

stands at least 30 stems per square foot.

Additional Criteria to Reduce Water Quality 

Degradation from the Transport of 

Nutrients Downslope

Minimum Row Grade. Follow the criteria 

outlined in the Additional Criteria to Reduce 

Sheet and Rill Erosion.

Maximum Row Grade. Follow the criteria 

outlined in the Additional Criteria to Reduce 

Sheet and Rill Erosion. 

Vegetation. Establish buffer strips to 

permanent sod-forming vegetation with stiff, 

upright stems.

Width of Strips. Buffer strips will be at least 

15 feet wide. Increase the buffer strip widths 

as needed to keep the width of the cropped 

strips uniform.

The maximum width of cropped strips will be 

one-half of the field slope length or 150 feet, 

whichever is less. 

Arrangement of Strips. In addition to the 

buffer strips established on the hillside, 

establish a buffer strip at the bottom of the 

slope. Make the bottom strip two times the 

width of the narrowest buffer strip in the 

system. 

Additional Criteria to Improve Soil Moisture 

Management Through Increased Water 

Infiltration

Row Grade. The grade along the upper edge 

of the buffer strip shall not exceed 0.2%

Width of Strips. The minimum width will be:

• At least 15 feet wide for strips planted to 

grasses or grass-legume/forb mixtures 

with at least 50% grass and 

• At least 30 feet wide when legumes/forbs

are used alone or legumes/forbs make up 

more than 50% of the stand.

Increase buffer strip widths as needed to keep 

the width of the cropped strips uniform. The 

width of the individual buffer strips may vary.

Cropped strips will be of uniform width 

between buffer strips and will not exceed 50% 

of the slope length (L), used for the erosion 

calculation.

Vegetation. Establish buffer strips to 

permanent vegetation consisting of grasses, 

legumes/forbs, or grass-legume/forb mixtures.

Establish species that are adapted to the site, 

and tolerant of the anticipated depth of 

sediment deposition. 

The buffer strips will have at least 95% ground 

cover during periods when erosion is expected 

to occur on the cropped strips.

The stem density for grasses and grasslegume/forb mixtures will be at least 50 stems 

per square foot, and for pure legume/forb 

stands at least 30 stems per square foot.

CONSIDERATIONS

General. Several factors influence the 

effectiveness of contour farming to reduce soil 

erosion. These factors include: 10-year, 24-

hour rainfall in inches; ridge height; row grade;

slope steepness; soil hydrologic group; cover 

and roughness; and slope length. Cover and 

NRCS, NHCP

September 2014
332 - 3

roughness, row grade, and ridge height can be 

influenced by management and provide more 

or less benefit depending on design.

Contour farming is most effective on slopes 

between 2 and 10 percent. This practice will 

be less effective in achieving the stated 

purpose(s) on slopes exceeding 10 percent 

and in areas with 10-year, 24-hour rainfall over 

6.5 inches. The practice is not well suited to 

rolling topography having a high degree of 

slope irregularity because of the difficulty 

meeting row grade criteria. 

This practice is most effective on slopes 

lengths between 100 and 400 feet. As slopes 

lengthen, the volume and velocity of overland 

flow are more likely to overwhelm the capacity 

of contour ridges and narrow buffer strips to 

contain them. Additional residue cover and 

other conservation techniques (including 

widening buffer strips) will decrease overland 

flow velocities, thus increasing the length of 

slope on which this practice is effective.

Contour buffer strips are more difficult to 

establish on undulating to rolling topography 

because of the difficulty of maintaining parallel 

strip boundaries across the hill slope or staying 

within row grade limits.

Areas of existing or potential concentrated flow 

erosion should be protected by conservation 

practices such as grassed waterways, water 

and sediment control basins, or diversion 

terraces.

Where contour row curvature becomes too 

sharp to keep equipment aligned with rows

during field operations, increasing the buffer 

strip width can help avoid sharp ridge points. 

In drainage ways, establishing grassed 

waterways at least up to the point of sharp 

curvature can allow the equipment to be lifted 

and/or turned to meet the same rows across 

the turn strip.

Prior to design and layout, remove any 

obstructions or make changes in field 

boundaries or shape, where feasible, to 

improve the effectiveness of the practice and 

the ease of performing farming operations. 

Prior to layout, inspect the field’s position on 

the landscape to find key points for starting 

layout or getting the width of one set of strips 

(one cultivated and one buffer) to pass by an 

obstruction or ridge saddle. 

Additional row markers consisting of field 

boundaries, hedgerows, fence lines, access 

lanes, terraces, etc. may be established as 

needed. Permanent vegetated buffer strips 

can serve as permanent contour or row 

markers to maintain design row grades during 

field operations.

Consider re-establishing the native plant 

community. Use native species that are 

appropriate for the identified resource concern 

and management objective. Consider 

vegetation that provides multiple benefits to 

improve other resources. 

Food and Cover for Wildlife and Beneficial 

Organisms. The following management 

activities may be carried out to enhance 

benefits for pollinators, natural enemies of crop 

pests, and wildlife benefits as long as they do 

not compromise the effectiveness of the buffer 

strips:

• Plant herbaceous species that provide 

habitat enhancement for the wildlife 

species, pollinators, or other beneficial 

organisms of concern.

• Add native forbs to the seeding mixture to 

increase habitat diversity or to provide 

pollen and nectar for beneficial insects.

• Mow the buffer strips every other year or 

every third year depending upon 

geographical location. The standing cover 

provides early and late season nesting and 

escape cover for many species of wildlife 

displaced from adjacent disturbed areas.

• Delay mowing until after the nesting period 

of ground-nesting species, but mow early 

enough to allow for regrowth before the 

growing season ends.

• To maximize nutrient interception, choose 

deep-rooted grasses that will efficiently 

remove nutrients that enter the soil profile 

within the buffer strip. Harvest hay 

regularly to remove surplus nutrients 

intercepted

PLANS AND SPECIFICATIONS

Prepare plans and specification for each field 

or treatment unit. Specifications shall describe 

the requirements to apply this practice to

NRCS, NHCP

September 2014
332 - 4

achieve the intended purpose.

As a minimum, record the following 

specification components in an approved 

Contour Buffer Strips, 332, Implementation 

Requirements document. 

• Percent land slope used for conservation 

planning;

• The minimum and maximum allowable row 

grades for the contour system;

• The designed widths of the buffer strips

• The species to be established in the 

buffers strips

• A sketch map or photograph of the field 

showing:

• The approximate location of the baselines 

used to establish the system;

• The location of stable outlets for the 

system;

• Width of equipment to be used on cropped 

rows.

OPERATION AND MAINTENANCE

Conduct all farming operations parallel to the 

strip boundaries except on headlands or end 

rows with gradients less than the criteria set 

forth in this standard.

Time mowing or harvest of buffer strips to 

maintain appropriate vegetative density and 

height for optimum trapping of sediment from 

the upslope cropped strip during the critical 

erosion period(s).

Fertilize buffer strips as needed to maintain 

stand density.

Mow or harvest sod turn strips and waterways 

at least once a year.

Spot seed or totally renovate buffer strip 

systems damaged by herbicide application 

after residual action of the herbicide is 

complete.

Redistribute sediment that accumulates along 

the upslope edge of the buffer strip/crop strip 

interface as needed. This sediment shall be 

spread evenly upslope over the cultivated strip 

when needed to maintain uniform sheet flow 

along the buffer/cropped strip boundary. 

If sediment accumulates just below the 

upslope edge of the buffer strip to a depth of 6 

inches or more, or stem density falls below 

specified amounts in the buffer strip, relocate 

the buffer/cropped strip interface location. 

Cultivated strips and buffer strips shall be 

rotated so that a mature stand of protective 

cover is achieved in a newly established buffer 

strip immediately below or above the old buffer 

strip before removing the old buffer to plant an 

erosion-prone crop. Alternate repositioning of 

buffer strips to maintain their relative position 

on the hill slope. If an established buffer is 

removed, a equipment width will be added to 

one crop strip and subtracted from another.

Renovate vegetated headlands or end row 

area as needed to keep ground cover above 

65 percent.

REFERENCES

Foster, G.R. and Seth Dabney, 2005. Revised 

Universal Soil Loss Equation, Version 2 

(RUSLE2) Science Documentation. USDAARS, Washington, DC. website: 

http://www.ars.usda.gov/sp2UserFiles/Place/6

4080510/RUSLE/RUSLE2_Science_Doc.pdf 

and 

http://www.nrcs.usda.gov/wps/portal/nrcs/main

/national/technical/tools/rusle2/ (verified March 

2014)

Renard, K.G., G.R. Foster, G.A. Weesies, D.K. 

McCool, and D.C. Yoder, coordinators. 1997. 

Predicting soil erosion by water: A guide to 

conservation planning with the Revised 

Universal Soil Loss Equation (RUSLE).U.S. 

Department of Agriculture, Agriculture 

Handbook 703. website: 

http://ars.usda.gov/SP2UserFiles/Place/64080

530/RUSLE/AH_703.pdf (verified March 2014)

USDA, NRCS. 2011, National Agronomy 

Manual, 4th Edition, Washington, D.C. 

http://directives.sc.egov.usda.gov/viewerFS.as

px?hid=29606 (verified March 2014)

X. Zhou, M.J. Helmers, H. Asbjornsen, R. 

Kolka, M.D. Tomer, and R.M. Cruse. 2014. 

Nutrient Removal By Prairie Filter Strips in 

Agricultural Landscapes. Journal of Soil and 

Water Conservation. Jan/Feb 2014-Vol. 69, 

NO. 1.

NRCS, NHCP

September 2014