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item Hagen, Lawrence
item Wagner, Larry
item Armbrust, Dean
item Skidmore, Edward

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 3/6/2000
Publication Date: 3/6/2000
Citation: Modeling for the 21st Century: thirty years of crop modeling: 2000 Mar 6-8, 2000; Temple, TX.

Interpretive Summary:

Technical Abstract: The primary purpose of the WEPS (Wind Erosion Prediction System) plant growth submodel (dubbed CROP) is to simulate production of biomass and its component parts by crop and non-crop plants. The amount of biomass produced produced determines how much residue may be available to provide protection from soil loss by wind and water erosion. In the arid and semiarid regions regions of the Western USA biomass production is highly variable. The primary cause of variability in biomass production is the weather, in particular precipitation and temperature. CROP calculates daily accumulation of biomass as a function of intercepted solar irradiance, and water and or temperature stress factors, thus accounting for the dominant factors of variability. However, yield, and therefore residue production, can be affected by many factors, including weeds, insects, salinity, slope, etc., as well as tillage practices such as no-till and minimum till. These and other factors are not currently accounted for by CROP submodel and could cause large differences between modeled average yields and observed long-term average yields at a given site. Failure to accurately estimate yield and residue production can lead to errors in calculations of soil loss by wind erosion. This research develped an automated method that adjusts modeled yield (and residue) when the WEPS user provides an observed yield as an iniput. An example of a county-level application fo the yield adjustment method follows: County-level average yield data of a crop are extracted from the National Agricultural Statistics Service (NASS) data files. If the modeled yield is significantly different than the county- level long-term average yields, a yield adjustment factor (YAF) is calculated.