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NRCS-MLRA 103 Soil Survey Project

The “Clarion loam, 2 to 6 percent” SDJR project encompassed map units within MLRA 103 totaling over 1.6 million acres, across 48 counties in the states of Iowa and Minnesota. This is one of the most extensive soils in MLRA 103, is Prime Farmland, and is considered a Benchmark soil. Products include:

MLRA Map Units with updated attribute data

  • Clarion loam, 2 to 6 percent slopes – This map unit is considered moderately well drained, and is found in fine-loamy, calcareous glacial materials in the low relief till plains common in the central and northern part of MLRA 103. It includes several re-advances of the Des Moines lobe from the continental ice-sheet
  • Clarion loam, Bemis moraine, 2 to 6 percent slopes – This map unit is considered well drained, and is found in loamy, calcareous glacial till on the southern Bemis moraine representing the terminus of the Des Moines lobe from the continental ice-sheet.


On-going water table studies are showing that the adage “many soils are wetter than we believe” to be true in most of MLRA 103. However a study conducted by Iowa State University on the Bemis moraine identifies deeper saturation than Clarion mapped elsewhere. The Bemis moraine has sandy loam textures below 85 centimeters and slightly higher sand content in the upper horizons relative to the central concept of the soil which identify loam textures. University of Iowa/Iowa Geological Survey lab data confirmed this trend in particle size, and their geologists supported the concept. Therefore a Bemis moraine phase was recognized due to coarser parent material and better defined landscape drainage.

Documented future needs

The Clarion series will continue to be evaluated based on the findings from the MLRA evaluations.

  • Future workload includes:
  • Modeling slope length on differing landforms to better support conservation planning.
  • Employing emerging spatial technologies to more accurately predict soil properties, soil-landscape relationships, and quantify ecosystem services.
  • Measuring water flow (Hydraulic Conductivity) to support water quality modeling.
  • Updating the soil laboratory database to further provide actual, rather than estimated data values. This includes collecting reference data such as organic matter, bulk density, and pH.
  • Investigating potentially thinner mollic horizons (i.e., less soil carbon) on the Bemis moraine.
  • Collecting Dynamic Soil Property data to improve data such as: productivity indices, Corn Suitability Rating(s), and to support the Soil Health Initiative.
  • Continuing investigations on depth to saturation and landscape hydrology in the Clarion concept across the unique landscapes identified in this project.

These issues for investigation are documented through the future projects:
MLRA 103 - Clarion loam, Bemis, 2 to 6 percent slopes
MLRA 103 - Clarion loam, central, 2 to 6 percent slopes

Depth to saturation is also being evaluated through the current project:
MLRA 103 - Clarion catena water table study

 NRCS-MLRA 103 Soil Survey Project