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United States Department of Agriculture

Agricultural Research Service

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Title: MODELING MULT-ROW WIND BARRIER DENSITY

Authors
 Fryrear, Donald - CUSTOM PRODUCTS & CONSULT Bilbro Jr, James Yates, Charles Berry, Ernest

 Submitted to: Journal of Soil and Water Conservation Publication Type: Peer Reviewed Journal Publication Acceptance Date: September 13, 2000 Publication Date: N/A Interpretive Summary: The use of hedge fences, shelterbelts or wind barriers to reduce wind damage to growing crops and protect the soil has continued since Samuel Deane fist experimented with locust trees in 1790. The interest in wind barriers continues even today, but to describe the protection offered by a wind barrier requires that the open space within the barrier be described. The open space allows the wind to pass through the barrier. A barrier with few open spaces is called a dense barrier. To describe the density of multi-row barriers requires expensive intruments and considerable time. ARS scientists have developed a way of computing the density of multi-row barriers with different densities in each row and with different spacings between the rows. This technique is called the EQUIVALENT OPTICAL DENSITY and can be used in new wind erosion equations. Technical Abstract: Multi-row wind reduction patterns can be expressed with a Barrier Effectiveness Index (BEI), but BEI cannot be used to model wind barrier effects on wind erosion. The effect of the wind passing through field barriers was simulated in a laboratory wind tunnel to develop an empirical relationship between BEI and total drag (r^2 = 0.79). Row spacings and densities between rows were tested to develop and verify an equation for computing the Equivalent Optical Density (EOD). EOD values were computed and then tested on additional field barriers, and the resulting correlation r^2= 0.92 was highly significant. With the EOD equation, wind barrier effects can be computed for barriers with up to 8 rows (N), any density (OD), or spacing between rows (RS). The EOD values can be used in wind reduction equations to compute wind reduction patterns for the Revised Wind Erosion Equation (RWEQ) model. This permits the evaluation of row numbers or plant density within each row to design wind barrier systems that will be most effective for the farmer.