The management submodel of the Wind Erosion Prediction System

Authors: Wagner, Larry; Fox, Jr, Fred

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2013
Publication Date: 6/1/2013
Publication URL: http://handle.nal.usda.gov/10113/58618
Citation: Wagner, L.E., Fox, F.A. 2013. The management submodel of the Wind Erosion Prediction System. Applied Engineering in Agriculture. 29(3):361-372.

Interpretive Summary: The Wind Erosion Prediction System (WEPS) is a process-based wind erosion model that predicts soil erosion by simulating the physical processes that impact wind erosion. The management submodel component of WEPS simulates the cultural practices used in crop land production, such as tillage, planting, cultivation, harvesting, irrigation, burning, etc. To do so, each specific practice or operation's impact on the soil, surface and vegetation is represented as a list of the physical processes causing those changes. Examples of such physical processes are the destruction of surface crust, flattening and burial of residue, mixing of soil layers, etc. The definitions and equations are presented for every physical process simulated within the WEPS Management submodel code.

Technical Abstract: The Wind Erosion Prediction System (WEPS) is a process-based, daily time-step, computer model that predicts soil erosion via simulation of the physical processes controlling wind erosion. WEPS is comprised of several individual modules (submodels) that reflect different sets of physical processes, e.g.: a) erosion (entrainment, transport and deposition of airborne particles); b) hydrology (water movement within the soil); c) plant growth (development of leaf, stem and reproductive plant components); d) residue decomposition (decay of plant materials); e) soil (surface soil conditions changed by daily weather conditions); and f) management (simulation of applied cultural practices). These submodels are supported by four databases: soil, management rotations (consisting of date listed operation and plant growth/decomposition records), wind barriers and weather, including wind data. The WEPS management submodel component attempts to simulate the effects of typical cropping management practices at an operation level such as tillage, cultivation, planting, harvesting, irrigation, residue burning, etc. upon surface conditions that modulate wind erosion. The variety of land management operations are simulated by identifying the primary physical processes involved and representing each individual operation as a sequenced set of those processes. They include: 1)surface modification (creation or destruction of ridges and/or furrow dikes that form oriented surface roughness, changes in surface random roughness, and destruction of soil crust); 2) mass manipulation (changes in aggregate size distribution and soil porosity, mixing of soil and residue among soil layers, and soil layer inversion); 3) biomass manipulation (burying and resurfacing residue, clipping standing residue, flattening standing residue, killing live crop biomass, and removing biomass); and 4) soil amendments (applications of residue/manure for cover, seeding or planting crops and irrigation water). The processes are simulated via a physical basis, if possible, incorporating conservation of mass concepts and relying on field and laboratory data for the functional relationships, if available. Because use of a minimum number of parameters with readily available and/or attainable values was a goal of submodel design, simplifications were made in representing some processes. Simulation of other processes was constrained simply by a lack of knowledge about those processes. However, because of its inherent design, the WEPS Management submodel, can be expanded and improved as new knowledge is gained relating to the physical processes affecting the soil, surface, and biomass due to human initiated (management) events. Also, because WEPS represents an operation as a sequence of physical processes, it not only allows for flexibility in how to describe specific operations, but also allows new implements to easily be created and used within WEPS.