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r <br />r 22 <br />~i*+~**~ wi11 have less fall time (aryl dLStanoe) to the soil surface thus <br />less surface thus less erosive energy. The average calculated erosion for the <br />reclamation area was 2.99 tons/acre/year, with a range fr'cmm 0.11 to 4.87. <br />Seeding of the reclamation arYa was done by seed drilling normal to the <br />slope. This introduces the erosion control practice factor (P) to the USLE. The <br />erosion control practice factor is defined as the ratio of soil lass with a given <br />surface condition to soil loss with up-ard-down hill plo~ring. Practices that <br />reduce the velocity of rwioff and the teniesx.-y of nmoff to flow directly <br />downslope reduce the P factor. In agricultural uses, (which approximate <br />reclamation practices) , P is users to describe plowing . arcs tillage practices. <br />When the erosion control practice factor is included in the USIE, erosion frtmm <br />the reclamation area averaged 1.74 t~s/acre/year, with a range frYmt 0.06 to 2.92 <br />(Table 7). The P factor cannot be applied to undisturi~ed soils. <br />M <br />Conservation Practice Factor (P) <br />The practice of tillage and planting on the contour is effective in reducing <br />soil erosion. In limited field studies, the practice provided almost ca~lete <br />protection against erosion frrmm storms of moderate to low intensity, but provided <br />little protection for storms that caused extensive brealaovers of the contoured <br />crows. Oontouring appears to be most effective on slopes of 3 to 8 percent <br />(Fjiar}+mnier and 57nith, 1978). <br />The effectiveness of contouring is also influenced by the slope length. <br />Sr'eakovers of corrtotlr rows may tern to concentrate werlarci flow arcs result in <br />increased soil erosion. A series of P values for contouring has been developed <br />for slopes arcs slope length limits (Table 8) (Wischmeier and Smith, 1978). These <br />limits on slope-length can serve as a planning tool. <br />