Soil Class Update

Modified on 2023/11/20 18:22 by Adam — Categorized as: Uncategorized

Update to Class on Soils Report

5/15/2015

The Irrigated and non-irrigated capability class on the soils report now defaults to Dominate Condition instead of weighted average on major components. This will align with the default settings on the NRCS web soil survey. Note: web soil survey does not have a weighted average for class.

Each soil type on the soils report is generally made up of 2 or more components and each component makes up a % of that soil type and has a capability class rating.

For Example Soil Type: "Kennebe-Nodaway silt loams, rarely flooded"

Has the following components:

Comp% compname majcompflag nirr-class
50 Kennebec Yes 1
45 Nodaway Yes 2
5 Zook No 2

Dominant condition will sum the Comp% for the class II soils for a total of 50% and compares that to 50% of the class I soil. In the case of a tie the most limiting soil(the class II) is used so this would be considered a class 2 soil.
The Surety soils report was using weighted average on major components only which would make this a class I soil.
This change will cause some class ratings on soil types to change on the soils report. Below is the percent of soil types where the class will change. Generally over ½ of these are class 5 or greater meaning they are not crop land. ND and SD have PI indexes so most people don’t look at class.


State Percent
ND 20.7
SD 14.6
MT 9.7
ID 8.0
OR 7.6
WA 6.0
OK 5.8
TX 5.2
MN 5.1
CO 4.7
KS 3.9
IN 3.8
NE 3.4
MO 3.0
AL 2.8
LA 2.1
GA 2.0
OH 1.7
IA 1.4
IL 0.6

The soils report will now contain an “*c” after the “non-irr class” and “irr-class” on the soils report with a foot note that says: “ *c: Dominant Condition Aggregation Method” to indicate the change.

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