AGVISE: 80 percent of Minnesota samples used zone testing

NORTHWOOD, N.D. -- As farmers strive to make the best use of their money in a down commodity price climate, an increasing number are choosing precision soil testing.

NORTHWOOD, N.D. - As farmers strive to make the best use of their money in a down commodity price climate, an increasing number are choosing precision soil testing.

AGVISE Laboratories Inc., based in Northwood, North Dakota, is a dominant handler of soil sample analysis in North Dakota, and is a significant player in the business with its second laboratory in Benson, Minn., serving clients in Minnesota and South Dakota. Officials say an increasing number of their soil samples are coming from so-called "zone" or "grid" samples, rather than the "whole field" model, which has been traditionally used.

John Lee, a soil scientist with the company, says AGVISE handles about a half-million samples a year for major crop consulting and fertilizer retailers in the region.

In 2016, about 80 percent of the soil samples from Minnesota were either grid or zone samples, compared to about 74 percent in South Dakota, 38 percent in Manitoba and North Dakota, and 27 percent in Montana, Lee says.

Dave Franzen, a North Dakota State University Extension Service soil scientist, says he's encouraged by the "trend line," but wishes it was higher. He thinks adaptation might be more significant in the east where there are more crop consultants advising farmers. "I hope that in the future, it's way higher," he says.


55 percent precision

Of the samples tested by AGVISE, the overall percent of more precision-level sampling has grown from about 40 percent in 2008 to 55 percent in 2016. All soil sampling has increased, but the number of precision samples handled in Northwood climbed from about 2,000 in 2003 to 17,000 in 2016. Similarly, the number of precision-based soil samples handled in Benson has climbed from about 1,000 in 2003 to more than 14,000 in 2016.

To compare, whole-field composite samples represent entire fields. In a typical situation in recent years, a quarter-section of about 160 acres might involve 15 to 20 soil core samples, which then would be blended and a single sample sent to a laboratory for testing.

"That's become less and less common because farmers see the yield go up and down in parts of the field because of yield monitors so they know all parts of a field shouldn't be treated the same," Lee says. More farmers are getting too much fertilizer, and parts aren't getting enough. Some areas of a field have limitations, including drown-outs or salinity, for example.

As needed

Zone testing typically identifies at least three areas of productivity within a field - low, medium and high. Soil sampling is done within those zones. "As we get squeezed with lower commodity prices, this activity increases," Lee says. "They don't want to put fertilizer on a portion of a field with no return and they want to apply it where it is needed."

MZB Technologies LLC, based in Watertown, South Dakota, started in 1998 and is now owned by Wheat Growers of Aberdeen, South Dakota. It is one of the companies in the region that has sprung up to capitalize on research led by NDSU, Lee says.

Jordan Tackett, an MZB Technologies regional sales manager for the Corn Belt, an area that includes southern Minnesota and South Dakota, says the company advises on 4.5 million acres of cropland in seven states. The high-quality techniques catch on faster where ag retailers are quicker to adapt. MZB stands for Management Zone Based.


MZB's zone sampling techniques are designed to be as accurate as 1.33-acre grids, Tackett says. MZB clients get yield potential goal-setting that ties in with variable-rate fertility and seed recommendations. The recommendations are based on layered data sets. The data include electro-conductivity data at one-foot and three-feet deep, as well as RTK satellite-based elevations and in-season satellite imagery of past crops.

Field size changes

Grid and zone sampling has become more important as field size has grown, Lee says. Some fields are about 320 to 640 acres, so increased numbers of zones within that square mile are useful. And productivity is something that can change because a farmer fixes or enhances areas within those zones, using techniques such as tile drainage or surface drainage.

Of course, in order to make precision sampling pay for itself, the farmers have to follow up with the application action. "You either have to manage it yourself, or hire someone to 'float' it on for you. If you don't have the ability to do precision application, there's no reason to split the field into parts."

University research is becoming geared toward getting the best economic returns on fertilizer, but often that's based on zone- or grid-sampling precision.

Grid sampling typically involves sampling at smaller increments. "That's more common in the heart of the Corn Belt, so it has more history with higher fertilizer rates," Lee says.

Lee says areas of grid sampling in southern Minnesota might not have the two-foot nitrate test that is standard in the Dakotas or northern Minnesota, where there is less rainfall. Southern Minnesota soils don't freeze as readily, so it's more reliable to do fertilization application recommendations based on previous-crop contributions of fertilizer.

"In North Dakota, we can test for nitrogen in the fall and know it's going to be there in the spring," Lee says. That's not true farther south, where nitrogen can be lost because soils freeze and thaw through the winter.

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