7. Small-grain equivalent of mixed vegetation for wind erosion control and prediction.
Agron. J., 84, 1992, pp. 98-101
The purpose of this analysis was to examine this discrepancy and derive an improved expression to determine the small-grain equivalent of mixed vegetation.
Control and prediction of wind erosion requires knowledge of the effectiveness of surface vegetative cover. Scientists realized early the value of crop residue for controlling wind erosion and reported quantitative relationships.
Amounts of wheat (Triticum aestivum L.) straw needed to protect most erodible dune sands and less erodible soils against strong winds were determined. Standing stubble was much more effective than flattened stubble. Standing sorghum (Sorghum bicolor (L.) Moench) stubble controlled wind erosion more effectively with rows perpendicular to wind direction than with rows parallel to wind direction.
Siddoway et al. (1965) quantified the specific properties of vegetative covers influencing soil erodibility and developed regression equations relating soil loss by wind to selected amounts, kinds, and orientation of vegetative covers; wind velocity; and soil cloddiness. They found a complex relationship among the different kinds and orientations of residue in terms of relative effectiveness.
The relative value of kinds and orientations of residue in controlling erosion must be quantified by soil, wind velocity, and variable characteristics of the residues.
Therefore, control and prediction of wind erosion require knowledge of the effectiveness of surface vegetative cover. The effectiveness is usually referenced to as small-grain equivalent. The procedure used to convert mixed vegetation to small-grain equivalent was found faulty.
Improper weighting of regression coefficients caused the conversion procedure to predict that adding crop residue decreased small-grain equivalent. Therefore, the purpose of this analysis was to improve the conversion of mixed vegetation to a small-grain equivalent. The new expression derived for this purpose gave a logical conversion where the previous procedure failed. It did not predict a decreasing small-grain equivalent with increased soybean (Glycine max (L.) Merr.) residue in the 0 to 300 kg/ha range as did the former method. Applied to the same data that were used for testing the previous procedure, the new procedure reduced the error by almost 50%. The new procedure improves the conversion of mixed vegetation to small-grain equivalent.
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Erosion and desertification control
Asia, Philippines, survey, technology transfer, farmer-participatory research
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