Concept
The maps of the forage species suitability zones are based on the concept that new GIS (Geographic Infomation Systems)-based mapping technologies and information systems can aid in developing agricultural and natural resource management systems that are economically sustainable.
This project is based on a collaborative effort to create a web-based, comprehensive knowledge resource to assist land managers and other decision makers in choosing forage and conservation species that are optimally matched with their environment.
The overall goal has been to improve agricultural productivity, natural resource management, environmental protection, and urban beautification using advanced computer technologies.
 
Process
To develop the species suitability maps, climate and soil factors are compared with species tolerances. Climate data is obtained from the PRISM Climate group at Oregon State University (https://prism.oregonstate.edu/). This group is recognized as the leading US climate data resource. Three factors are used: 1) annual precipitation, 2) January minimum temperature (Tmin), and 3) July maximum temperature (Tmax). Soil data is obtained from the USDA's Natural Resources Conservation Service (NRCS) from the STATSGO2 database (https://catalog.data.gov/dataseet/u-s-general-soil-map-statsgo2). Factors used to evaluate forage suitability are soil pH, soil drainage, and soil salinity. 
 
We recognize that there are other factors important in climate and soil conditions, but defining a manageable number of factors has been an important consideration. 
 
Creating functions
Response functions for each of the six factors were developed with R Statistical Software and Python programming language. Logistic functions were used for precipitation, Tmin, and Tmax. A Gaussian function was used for pH and drainage. An exponential function was used for salinity.
 
Data for tolerance values and yields were obtained from the USDA NRCS National Range and Pasture Handbook and other online research and extension-based resources.
 
Four suitability zones were based on potential yield:
  • <25% yield = Unsuited
  • >25% to <50% yield = Marginally suited
  • >50% to <75% yield = Moderately suited
  • >75% yield = Well suited

GIS tools

ArcGIS Pro was used as the GIS tool. A map atlas was created by making an index layer with a georeferenced polygon over the U.S. for each species and parameter.  Suitability layers were created by running the Python code laid over a separate layer.  Maps were exported at PNG files for the website.

Nine maps are being developed for each species; one for each of the climate and soil factors, a combined climate map, a combined soil map, and a comprehensive map combining all factors.  This will allow users to eliminate factors that do not limit their production. For example, if forage is irrigated, eliminate the precipitation factor, or if drainage lines are in place, eliminate soil drainage.

Support

Primary funding for the mapping and species information work has been provided by the AFRI Sustainable Agricultural Systems Coordinated Agricultural Project (SAS-CAP) grant no. 2021-68012-35917 from the USDA National Institute of Food and Agriculture.  Prior to this project, funding for marketing grass and clover seed was provided by the USDA's Foreign Agricultural Service Emerging Markets and Market Access Programs, the International Cooperation and Development's Research & Scientific Exchanges Division, the Oregon Seed Council, Oregon Tall Fescue Commission, Oregon Clover Commission, and the Oregon Economic & Rural Development Department.