Location: Watershed Physical Processes ResearchTitle: Forage harvest representation in RUSLE2) Author
Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/11/2013
Publication Date: 1/10/2014
Citation: Dabney, S.M., Yoder, D.C., Ferruzzi, G. 2014. Forage harvest representation in RUSLE2. Agronomy Journal. 106(1):151-167. Interpretive Summary: The Revised Universal Soil Loss Equation, version 2, (RUSLE2) is widely used by NRCS to determine farm program eligibility and for developing conservation plans. In earlier versions of RUSLE2, it was very difficult to develop good descriptions of hay and pasture lands. A new technique for modeling perennial forage production has been implemented in RUSLE2 that is easier to use and results is more accurate estimates of runoff and erosion from hay and pasture lands. The resulting erosion estimates are usually lower than from the older approach. This report provides details and examples for developing land management descriptions using the new perennial vegetation modeling technology in RUSLE2 and describes the NRCS database that has been developed. When implemented as the official version of RUSLE2 by NRCS, this new technology will increase the conservation credit given to well managed forage areas.
Technical Abstract: The Revised Universal Soil Loss Equation (RUSLE and RUSLE2) has long been used by 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, ignoring the normal death of vegetative residue and 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, as described and validated in Dabney and Yoder (2012). A complementary comprehensive RUSLE2 harvest process developed to interact with the new vegetation growth model is described in this report. This harvest process includes an extensive set of options that provide great flexibility in describing perennial vegetation management systems. The ability of the new growth model and harvest process to dynamically adjust residue creation in response to alternative forage harvest schemes is illustrated 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/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.