Other Factors – FFA Land CDE

By Donald G. McGahan, Ph.D.
Revised: April 9, 2017


I have always been taught and told that wetness as a factor makes a site a land class 3. However, I cannot find that written in any manual. Is this correct?
No. Wetness keeps the land out of Class I. Installing drainage systems on wet Class V land is typically not economical and is not recommended for the FFA Land CDE. Under Other Factors on page 8 of the Land Judging Manual Oklahoma under Wetness it mentions a category of “moderately-wet” as if it was a Wetness Class. Coaches and the high school kids likely do not have any idea what that is or how to determine moderately-wet from any other. For simplicity sake, if you see the site (or field) conditions having  Wetness, you can proceed using practice 18 under treatments unless it is a Deep soil as determined in Part 1. For Deep soils that have Wetness the condition sheet will have to provide an alternate Surface Runoff term. It is probably self evident that a soil with Wetness might have Very Slow Surface Runoff but this may not be the case! All slopes classes are allowed in Table 5. Therefore, Deep soils with Wetness will have to have a Surface Runoff given to modify the Wetness as follows:

Wetness: Mod. Wet
Wetness: Wet
Wetness: Flooding

The wording in the Land Judging Manual Oklahoma is contradictory, but this is perhaps the best way to handle this. This does not get the student out of the box of having contradictory and conflicting Surface Runnoff terms used in Part 1 and Part II. To further reduce confusion the official might consider adding to the condition sheet the desired response for Surface Runoff in Part I. For more information not specific to the FFA Land CDE, but for edification 🙂 Wetness is actually a term used in describing Drainage Class, and the Classes —or categories– of Drainage Class are used in arable and non-arable soils. I have a thumbnail description of the Soil Drainage Categories at http://bionicprofessor.com/soil-drainage-classes/ From the National Soil Survey Handbook

618.16  Drainage Class

A.  Definition.—“Drainage class” identifies the natural drainage condition of the soil.  It refers to the frequency and duration of wet periods.

B.  Classes.—The eight natural drainage classes are listed below.  Chapter 3 of the Soil Survey Manual provides a description of each natural drainage class.

(1)  Excessively drained
 (2)  Somewhat excessively drained
 (3)  Well drained
 (4)  Moderately well drained
 (5)  Somewhat poorly drained
 (6)  Poorly drained
 (7)  Very poorly drained
 (8)  Subaqueous

C.  Significance.—Drainage classes provide a guide to the limitations and potentials of the soil for field crops, forestry, range, wildlife, and recreational uses.  The class roughly indicates the degree, frequency, and duration of wetness, which are factors in rating soils for various uses.

D.  Estimates.—Infer drainage classes from observations of landscape position and soil morphology.  In many soils the depth and duration of wetness relate to the quantity, nature, and pattern of redoximorphic features.  Correlate drainage classes and redoximorphic features through field observations of water tables, soil wetness, and landscape position.  Record the drainage classes assigned to the series.

E.  Entries.—Enter the drainage class name for each map unit component.  Use separate map unit components for different drainage class phases or for drained versus undrained phases, where needed.”

End


In Land on the additional info of the condition sheet if it were written occasional flooding would it be a major factor and class V. I believe flooding is flooding. I can’t find anywhere in the land section where it states what occasional or frequent means.
I am going to use the USDA-NRCS National Soil Survey Handbook  Part 618 (Subpart A) at 618.30 as part of the information to address this. First, contradictions do exist in the Land Judging Manual Oklahoma.

strong>Flooding is an "Other Factor" that can be added to the FFA Land CDE condition sheet for a field and on page 8 it states:
Flooding is not considered on slopes over 3 percent. Flooding would place an area in Class V. Practices 14 and 20 would be possible treatments.

A contradiction for Deep soils is that the guide also has Flooding listed as a Surface Runoff within Table 5 on page 11. It is likely that a judger will be confused here because on page 5 the guide states:

Four classes of runoff are recognized in Oklahoma land judging.

These four classes of runoff listed on page 5 are Rapid, Moderate, Slow, and Very Slow. There is no mention of the Runoff Classes of Mod. Wet, Wet, and Flooding listed in Table 5. Furthermore, in Table 5 it states that “All” slopes might fit in a “Surface Runoff” of Flooding. As a career soil judgers treat Drainage Class (often confused with Wetness) and Flooding separately even though they are –like so many things– related.

Flooding Frequency Class.—Flooding frequency class indicates the number of times flooding occurs over a period of time.

The Flooding Frequency Class of “Frequent” is:

Flooding is likely to occur often under usual weather conditions; more than a 50 percent chance of flooding in any year (i.e., 50 times in 100 years), but less than a 50 percent chance of flooding in all months in any year.

The Flooding Frequency Class of “Occasional” is:

Flooding is expected infrequently under usual weather conditions; 5 to 50 percent chance of flooding in any year or 5 to 50 times in 100 years.

The “Land Judging in Oklahoma” states “or frequent flooding” as one of the limitations that might place it in Class V and “unsuitable for cultivation. However, in Table 5 no mention of “Flooding Frequency Class” are evoked. Just occasional flooding alone is not enough to place it into Class V for the FFA Land CDE. But, note that if it were deemed to have “very poor surface and internal drainage” that can also place it in Class V for the FFA Land CDE. Perhaps where Land and Homesite CDE’s are separated, as they often are in Texas, there is a disservice to the student. Try reading Page 18 in the Homesite CDE section for more on what the Guides authors were intending. What is internal drainage? Drainage class” identifies the natural drainage condition of the soil. It refers to the frequency and duration of wet periods. “Very poorly drained” is a class within the “Drainage Class” classification.

618.16  Drainage Class

A.  Definition.—“Drainage class” identifies the natural drainage condition of the soil.  It refers to the frequency and duration of wet periods.

B.  Classes.—The eight natural drainage classes are listed below.  Chapter 3 of the Soil Survey Manual provides a description of each natural drainage class.

(1)  Excessively drained
 (2)  Somewhat excessively drained
 (3)  Well drained
 (4)  Moderately well drained
 (5)  Somewhat poorly drained
 (6)  Poorly drained
 (7)  Very poorly drained
 (8)  Subaqueous

C.  Significance.—Drainage classes provide a guide to the limitations and potentials of the soil for field crops, forestry, range, wildlife, and recreational uses.  The class roughly indicates the degree, frequency, and duration of wetness, which are factors in rating soils for various uses.

D.  Estimates.—Infer drainage classes from observations of landscape position and soil morphology.  In many soils the depth and duration of wetness relate to the quantity, nature, and pattern of redoximorphic features.  Correlate drainage classes and redoximorphic features through field observations of water tables, soil wetness, and landscape position.  Record the drainage classes assigned to the series.

E.  Entries.—Enter the drainage class name for each map unit component.  Use separate map unit components for different drainage class phases or for drained versus undrained phases, where needed.”

For edification you might want to see my web blog on soil drainage classes at http://bionicprofessor.com/soil-drainage-classes/. End


 

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