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An equation that estimates potential wind erosion requires that all vegetative cover (dry weight per area) be expressed as a small grain equivalent. Wind-tunnel tests were used to determine that equivalent for selected range grasses, either as single species or mixtures, at three grazing-management levels. Compared with flat small grain, range grasses evaluated effectively prevented erosion, with buffalograss (Buchloe dactyloides) the most effective and big bluestem (Andropogon gerardi) the least effective among those tested. A possible procedure for extending the results to other grasses or mixtures is suggested. The data on range grass to small grain equivalent for erosion control may be used to predict the wind erosion potential of range sites or to determine the amounts of range grass needed to hold potential erosion to tolerable limits. Managing vegetative cover is the most effective practical method for controlling wind erosion (Woodruff et al. 1977). Effectiveness of wind erosion control depends on the quantity, kind, and orientation of vegetation in relation to the soil surface (including areal distribution) (Chepil 1944; Siddoway et al. 1965; Lyles and Allison 1976). Current procedures for evaluating or designing management systems for wind erosion control utilize the following equation (Woodruff and Siddoway 1965): E =flI, K, C.L. V), 111 where E is the potential annual soil-loss rate; I, the soil erodibility; K, the soil ridge roughness factor: C, the climatic factor; L, the unsheltered distance across a field along the prevailing wind erosion direction; and V, the equivalent vegetative cover. To use the equation, one must express all vegetative cover (dry weight per unit area) in terms of its equivalent to a small grain standard. The standard (reference) has been defined as 25.4 cm of dry small grain stalks lying flat on the soil surface in rows perpendicular to wind direction with 25.4-cm row spacing, with stalks oriented parallel to the wind direction. Although equivalents data are available for several agronomic crops, none have been obtained for range grasses. Consequently, we initiated this study to determine the small grain equivalents of several perennial range grasses as single species or mixtures at three levels of simulated grazing management. Experimental Procedure Native perennial range grasses made available by the U.S. Dep. Authors are agricultural engineer, Science and Education Administration, Agricultural Research, U.S. De artment of Agriculture; and research assistant, Agronomy De artment, Kansas &i I tate University, Manhattan, respectively. IS research is a contribution from the Sci. and Educ. Admin., Agr. Res., U.S. Dep. Agr., in cooperation with the Kansas Agricultural Experiment Station. Dep. of Agronomy Contribution No. 79-61-J. Manuscript received December 28, 1978. Agr., Soil Conservation Service, from ungrazed sites in Nebraska were buffalograss (Buchloe dactyloides), sideoats grama (Bouteloua curtipendula), western wheatgrass (Agropyron smithii), and needleandthread (Stipa comata). Big bluestem (Andropogon gerardi), little bluestem (Andropogon scoparius), switchgrass (Panicum virgatum), and blue grama (Bouteloua gracilis) were obtained from the Plant Materials Center, Manhattan, Kansas (Table 1). All grasses were harvested after dormancy with 5.1 cm of intact roots for anchoring. In the laboratory, the plants were washed and air-dried before wind-tunnel testing. Properly grazed and overgrazed management levels were simulated by clipping the ungrazed material to various heights (Table 1). The wind-tunnel, 1.52 m wide, 1.93 m high, and 16.46 m long, was a recirculating push-type tunnel with airflow generated by a loblade, variable-pitch axivane fan. The appropriate kind, amount, and height of grass was placed in standard test trays 148 cm long, 16.5 cm wide, and 4 cm deep (inside dimensions). The trays were then filled with sand 0.297 to 0.42 mm in diameter so that the grass stood in clumps, and were exposed for 5 minutes at 13.36 m/set freestream Table 1. Heights of standing perennial range grasses that were evaluated in a wind tunnel at three levels of grazing management for wind-erosion protection. Grass species Height (cm) properly OverUngrazed grazed grd Symbol

Range Grasses and Their Small Grain Equivalents for Wind Erosion Control