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Giddings 4' hydraulic soil probe mounted onto a John Deere Gator
In 2008 we made the move to WardLabs for all of our soil, tissue and manure/compost analyses.  When we were certain that we could place a high degree of confidence in the results we were obtaining, we decided to move a little deeper than typical surface 0-8 inch soil samples.
Table 2. Lbs of Nitrogen/foot of soil per Client - 2010 Data
That same year we began taking samples to 3 feet – having a complete analysis performed in the top foot, and analyzing for nitrate nitrogen in the 2nd and 3rd foot.  Acquiring cores from the 3rd foot on ground that had been in cotton the previous year, was rather difficult.  This past season, the fall of 2010, we purchased an hydraulic probe from Giddings (Photo to the right and lower left) that had a rotating head, and the saw tooth bit.  We then had the ability to easily go to 3’ in very hard ground, and 4’ otherwise.  Now we analyze for nitrogen and sulfur at 1’, 2’, 3’ and 4’.  By doing so, we have been able to track total nitrogen in the soil profile for the previous three years for our clients.
Samples are taken within management zones.  These zones are created using the previous three years of aerial images, yield maps (if available) and now beginning to modify zones with EC maps (VERIS).  We log each point with real world coordinates, in order to eliminate as much variability as possible.  Cores are taken within a 5-10 foot radius of those in previous years.  All data and points are processed and managed via Farmworks Office Pro/GIS.
Table 1 is a graphic representation of nitrogen use, per client, from 2008-2010.  We are now much better able to tell if we are accumulating nitrogen (over applying), or ‘mining’ that deep nitrogen (under applying).  
Table 1.  Lbs of Nitrogen/Client/3' Profile - 2008-2010
Dr. Brent BeanTexas Agri-Life, Amarillo, Texas, conducted some of the early research in West Texas with soil electrical conductivity.  The equipment that he used was a VERIS 3100 - Veris Technologies.  Some very extensive work is currently ongoing in Mississippi, through the efforts of Dr. Jeff Willers and Mr. Pat English.

One of the most recent pieces of that precision ag puzzle is having the ability to map electrical conductivity across a field, and correlate that to soil type, salinity, and high/low productive areas within that field.  We are in the process of acquiring data on our first two fields that will be planted this spring using a variable rate planter. Variable rate planting (VRP) maps will be created by kriging/merging data from these EC maps and multiple years of yield maps and three years of aerial IR imagery.  

Once we have EC data, then moving on to variable rate irrigation (VRI) will be a much simpler matter – late 2011 or early 2012.  When we have the ability to variably irrigate via the pivot, we also have the ability to apply variable rates of nitrogen via those pivots.  With the increasing costs of nitrogen, energy, and impending water regulation, it appears that we will see systems being retrofitted in the very near future.

Data from VERIS - Soil Texture as % Sand/Silt/Clay
and Salinity. Courtesy of Veris Technologies.
Map genterated using shallow (0-12:") and deep (0-36") data.
Courtesy of Veris Technologies
Veris data, Shallow (0-12"), Jase Merritt Farms, 2011
Processing courtesy of Dr. Jeff Willers, USDA/ARS, Mississippi State Univ.
Veris data, Deep (0-36"), Jase Merritt Farms, 2011
Processing courtesy of Dr. Jeff Willers, USDA/ARS, Mississippi State Univ.
Nitrogen, pounds/acre/foot of soil, for 2010 was tabulated for each client (Table 2), and those values are used in making recommendations for the next season.