Inventory the Resources

The first step in assessing the possibility of a wind erosion resource concern is to consult the appropriate Soil Survey for the area of interest. All NRCS soil survey data can be found online using the Web Soil Survey tool.32 In Web Soil Survey, after selecting the Area of Interest, select the Soil Data Explorer tab, and then the Soil Properties and Qualities tab, and finally Soil Erosion Factors. The wind erosion factors are made up of the Wind Erodibility Group (WEG) and the Wind Erodibility Index (WEI). Although these factors were originally intended to serve as indices for the Wind Erosion Equation (WEQ) on cultivated land, which NRCS has abandoned for use as a wind erosion model, the values can still be used to gauge the soils’ susceptibility to wind erosion for the selected area. WEGs range from 1 through 8, where group 1 is very highly erodible and group 8 is not susceptible to wind erosion. WEG is further explained in the National Soil Survey Handbook,47 Part 618 (see Appendix B, Exhibit 5-2). 

The WEI is the base variable in the WEQ and represents the potential erodibility of a soil, expressed in tons/ac/year before any other variables are applied through the equation. Keep in mind that the WEG and the WEI were intended to be used only on cultivated lands. However, these values can also serve as an indicator where there may be resource concerns on rangeland or other associated agricultural lands. Likewise, the Ecological Site Description (ESD) might provide some insight to the susceptibility of the site to wind erosion in various states. States are currently developing ESDs to a new standard; as ESDs become more robust in their interpretations, they will have increasing value for the inventory stage of conservation planning.

On cropland, identifying a wind erosion resource concern can be as simple looking for field clues. Wind-blown soil will deposit in field ditches, crop furrows, along fencerows, in low areas, and at the windward base of any wind barrier, including walls or even a sign post. Even the crops themselves or in adjacent fields might show evidence of sandblasting. Oftentimes, sandblasted seedlings will quickly desiccate, wither, and die.

As discussed in Chapter 3, the tool used to evaluate and estimate soil erosion on cropland is the Wind Erosion Prediction System (WEPS), now integrated into the NRCS Integrated Erosion Tool. The tool, developed by USDA Agricultural Research Service, is the model NRCS has determined provides the best estimation of erosion (expressed as tons/ac/year) over the wide range of soil and climatic conditions, agronomic systems, erosion control methods, and tillage equipment used across the Nation. It is important to note that the system provides an estimation of erosion, and it is not an absolute value. By accounting for local climatic conditions, on-site soil conditions, exact crops grown and their planting and harvesting dates, irrigation or lack thereof, and the tillage and harvesting equipment used, the model is very good at evaluating alternative cropping systems. This allows the planner to easily adjust planting and harvesting dates, alter irrigation scheduling, reorganize tillage patterns, and select different crops to offer the farmer alternatives that would make the least impact on the soil resource.



32.  Web Soil Survey.

47.  U.S. Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI.