Soil Surveys and Precision Agriculture

Winter meeting have begun and we have been busy with them.  Two weeks ago at the 2nd annual AgData Conference in Iowa City we heard two presentations about the shortcomings using soil surveys to define management zones for precision agriculture.  Tom McGraw, consulting soil scientist brought up the issue in his presentation on the Flaw of averages.  Afterward, I had a discussion with him about the topic.  His comment was that the USDA Soil Survey is the best in the world, but it is not good enough in many cases, to make site specific management decisions.  The Veris tool is a popular way to define management zones based on Electrical conductivity and soil color.  I have seen the Veris work very well and I have seen it not work well. 

Shannon Gomes, like me an old USDA soil scientist made a similar presentation later on.  Gomes is using lots of deep soil borings and an EM meter to define ones.  Gomes says that rather than try to use all the standard soil features to define ones, we can narrow it down to a few such as topsoil texture, color and depth, subsoil texture and dept, available water holding capacity,  and cation exchange capacity.  His methodology sounded kind of expensive, but considering that the work should last, until further refinement is necessary, perhaps it is not too bad.  Gomes did mention that he is looking over all at the five factors of soil formation.  They are:

1. Parent Material
2. Biota (including native vegetation)
3. Topography
4. Climate
5. Time

We try to refine the soil survey in by using GPS to define the boundaries between soils that have similar management considerations based on the five factors of soil formation.  We sometimes end up with rather large ones that contain similar soils,  The large zones are broken down further to end up with 10 acre or smaller zones.  Our process is not expensive, but require us to be o n the ground, and it requires a trained eye.  The photograph below shows zone boundaries as I have defined them in Pike County.  The purple lines are the Soil Survey lines.  You can see that we are gaining signifigant refinement with a relatively simple process. 

Pike County Soil Survey vs GPS defined zones.