Interpretation of Soil Factors – FFA Land CDE

Questions about Interpretation of Soil Factors

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

Previously Texas had it’s own guide to FFA Land Career Development Events, but the Texas FFA Board of Directors (BOD) have decided to use the Land Judging Manual for Oklahoma. This decision might have been driven by a desire to adopt the State Manual where the National FFA events have been customarily been hosted.

In an instance where the surface soil texture is moderately coarse and the subsoil texture is course. The Texas and Oklahoma Guides seem to have a contradiction with respect to permeability. I have heard over the last few years that Oklahoma rules trump Texas rules. What do I do?

Texas Guide said on page 6 “permeability should be based upon the most limiting horizon regardless of its position in the soil profile.” The Oklahoma Guide says in the second paragraph of Permeability on page 5 left hand column, and in the shaded box on page 5 at the top of the right hand column:

 ...the subsoil texture sample in the box will be used to determine permeability.

Trust that the Event Steward would have liked to choose a different site that makes their efforts less stressful. However, with the time investment necessary to get permission to excavate from Texas811locate and the excavation time itself it is often logistically unsound to move the site when these conditions present themselves.

The career soil scientists chooses the most limiting horizon as stated in the Texas Guide. However, Texas no longer uses the Texas Guide. It is retired by the Texas FFA BOD regardless of it being more correct. The FFA Land CDE in Texas FFA now uses the Oklahoma guide. Therefore, the marked subsoil texture sample in the box, bag, or bucket is to be used to determine the permeability.

Soils influenced by over-banking of water courses –either in the past or presently– are not uncommon in many parts of Texas. Often this results in a surface texture that is finer –heavier– than the subsoil texture. This one is not going away. Event sites will continue to be excavated on these landscapes.

Please have patience with the professionals who are stewards at these excavations. It is difficult to adjust to recording incorrect information for the sake of an FFA Event.

My question involves permeability. Again, in the Oklahoma guide, permeability is defined as a function of texture. Coarse texture has rapid permeability, moderately coarse and medium textured soil has moderate permeability, moderately fine soil has slow permeability, and fine soil has a very slow permeability. Is this how we determine permeability in our Texas State contest? As I read the Oklahoma book, it does not mention soil structure in determining permeability. The permeability is strictly based upon the soil texture. I was hoping you could clarify this for me.

Since adoption of the Land Judging in Oklahoma manual by the FFA BOD structure is no longer considered for the FFA Land CDE. Collegiate judgers do account for structure. Professional judgers also do account for structure. NOT the highschool FFA Land CDE. Just subsoil texture that is presented and marked in the bag, box, or bucket by the Event Steward.

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