RUSLE2-GRAZE: Predicting Management Effects On Residue Production and Soil Erosion.

Calculating residue production only during periods of canopy decline or in response to operations underestimates residue cover creation, resulting in overestimates of soil erosion from pasture and hay lands. To solve this problem, new vegetation routines were developed for RUSLE2 that better reflect the amount of residue added by perennial vegetation during its growth, and that make it is easier to model haying/grazing scenarios. The new routines improve prediction of the impact of management on plant growth, forage harvest, residue returns, and soil erosion. Work conducted jointly by the USDA-ARS, the University of Tennessee, and the USDA-NRCS has resulted in the creation of version of RUSLE2 that includes a “vegetation wizard” allowing advanced users to create vegetation descriptions that respond to management in realistic ways. Users describe the potential growth of vegetation in terms of: total annual production under good management, monthly production percentages, the average lifespan of vegetation, maximum canopy and height at peak live biomass, the cutting height that allows potential growth, and the tendency of the vegetation to thicken (form a sod) in response to repeated defoliations.  Potential yield levels are changed to reflect different fertility or available water levels and the program automatically calculates the effects of cutting or grazing management alternatives on forage harvested and the amount of above and below ground residues that are returned to the soil. The resulting vegetation descriptions are brought into erosion calculations using normal the RUSLE2 operation/management approach.  USDA-NRCS grazing specialists are in the process of developing regional databases of vegetation descriptions that will allow the new capabilities of RUSLE2 to be used in field offices nationwide. The new version of RUSLE2 will allow erosion estimates to be a factor considered as part of grazing planning.