Forage Harvest Representation in RUSLE2

Abstract

The Revised Universal Soil Loss Equation (RUSLE and RUSLE2) has long been used by the USDA and others for management planning based on soil erosion and sediment delivery estimates. It has worked well for normal annual agronomic crops but proved to be awkward for forage crops. This is partly because RUSLE and earlier versions of RUSLE2 calculated vegetative residue production only during periods of canopy decline or in response to management operations, resulting in underestimation of residue amounts, with subsequent overestimation of soil erosion from pasture and hay lands. To solve this problem, a new vegetation model was implemented in RUSLE2 to track the growth, death, and characteristics of perennial vegetation. A complementary comprehensive RUSLE2 harvest process developed to interact with the new vegetation growth model was also developed. This harvest process includes an extensive set of options that provide great flexibility in describing perennial vegetation management systems. In this study, the ability of the new growth model and harvest process to dynamically adjust residue creation in response to alternative forage harvest schemes was investigated through comparison with published studies involving bahiagrass (Paspalum notatum Flügge), bermudagrass [Cynodon dactylon (L.) Pers.], and ryegrass (Lolium perenne L.). The new modeling tools make it easier to model haying and grazing scenarios in perennial systems, to create better estimates of the amount and timing of plant residue added by perennial vegetation during its growth, and thus to improve runoff and soil erosion estimates for conservation planning.