Corn Suitability Ratings & Soil Interpretations

CSR2 (Corn Suitability Rating 2) is an index used in Iowa to rate the productivity potential of soils for row-crop agriculture, especially corn. It ranges from 5 to 100, with higher values indicating better soil quality and yield potential. CSR2 is based on soil properties, climate, slope, and landscape position, and provides a standardized way to compare farmland productivity across the state. It replaced the original CSR system to improve consistency and transparency using updated soil data and models.

CSR2 Equation and Methodology

CSR2 Equation and Component Values – Equation (Mar 2015)

CSR2 Maps and Visual Data

County Weighted Average CSR2 – Map (May 2017)
Iowa CSR2 Distribution – Map (Jan 2016)

Guides and Articles

ISU Extension: Computing the Iowa Corn Suitability Rating for Your Farm – Article (Jun 2014)
Iowa Farmer Today: ISU Tweaks CSR – Article (May 2015)
Integrated Crop Management News: CSR2 Equation Updated – Article (Apr 2015)

Comparison and Background

A Comparison of Iowa’s Original CSR Index to the New CSR2 Index – Poster (Apr 2015)
CSR2 Background, Update, and Frequently Asked Questions – FAQ (May 2013)
ISU CALS: ISU Updates Method for Rating Soil Productivity – News Release (May 2013)

Additional Maps and Context

Major Land Resource Areas (MLRA) within Iowa – Map (May 2015)
USDA-NRCS Areas and Office Locations within Iowa – Map (May 2015)
Average Precipitation for Iowa (1981–2010) – Map (Sep 2012)

Regional and Soil Association Maps

Landform Regions in Iowa – Map
Soil Associations of Iowa (STATSGO Database) – Map
Principal Soil Associations and Major Soil Areas in Iowa – Map

Soil Order Distribution Maps

Distribution of Alfisols in Iowa – Map (2013)
Distribution of Entisols in Iowa – Map (2014)
Distribution of Histosols in Iowa – Map (2013)
Distribution of Inceptisols in Iowa – Map (2013)
Distribution of Mollisols in Iowa – Map (2013)

Topography, Slope, and Capability Data

Estimated Iowa Farmland by Slope Gradient – Figure (2015)
Summary of Slope Ranges Within Each Slope Class – Table (Oct 2013)
By-County Land Capability Class (LCC) Summary – Table (Jan 2011)
Iowa Land Capability Class (LCC) Distribution – Map (Jan 2016)

Soil Rankings and Carbon Index

Summary of Soil Orders in Iowa – Table (Nov 2013)
Top 10 Soil Series and Map Units – Table (Mar 2010)
County Weighted Average Carbon Index – Map (Apr 2005)

These keys provide a simplified way to identify and compare dominant soils within two major soil regions of Iowa: loess-derived soils in the east-central region and prairie-derived upland soils in the northwest. Each key classifies soils based on properties such as parent material, organic matter, drainage, and landscape position. Understanding these associations helps guide land use, management decisions, and conservation planning across Iowa’s diverse agricultural landscapes.

Explore our Map Library to access a wide range of resources, including high-quality images, downloadable GIS data, and our interactive Soilscapes map—designed to visualize soil patterns and land use across Iowa and Nationwide.