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Solid Data Drives Input Decisions

16:17PM Mar 26, 2019
Data layers

We can’t have too many good layers of good data. But we can easily have too much bad data. One bad layer can cause us to make a costly mistake as we implement VIT.( Lindsey Benne )

Garbage in, garbage out. Remember that old computer adage? Your variable-input management plan will only be as effective as the information upon which it is based.

“The foundation for a sound variable-input technology [VIT] program is collecting accurate data,” says Farm Journal Field Agronomist Ken Ferrie. “Mere information isn’t sufficient—it must be high-quality, accurate data.”

Reliable historical data lets you identify strengths and weaknesses of soil management zones and hybrids. VIT lets you make plans to take advantage of the strengths and manage around the weaknesses. With VIT, collecting data becomes an important, ongoing process—the more data you have, the more accurate your management decisions will be.

The layers of data are the bricks in the foundation of your VIT plan. You will want to collect data from many levels—from the height of a satellite, to the tractor and combine seat, to boots on the ground.

“We can’t have too many good layers of good data,” Ferrie emphasizes. “But we can easily have too much bad data. One bad layer can cause us to make a costly mistake as we implement VIT.”

The first level of data comes from your analysis of each field, looking for strengths and weaknesses. “Start collecting data with a calibrated yield map,” Ferrie says.

“Not all yield maps are useful, so begin by separating bad maps from good ones,” he adds. “When you look at a calibrated map, you can quickly tell the areas of high and low yields in a field. Those zones will jump off the page.”

But that information won’t be there unless the map was made with a calibrated yield monitor. “If the monitor was not calibrated, the map will not show spatial variability,” Ferrie says. “It may show a total yield close to the one on the scale ticket, but it will be impossible to identify high and low yield zones.

“If you have to use kriging software, which estimates unknown values based on known values at other locations, to produce a map that shows special variability, you don’t have a calibrated yield map. If this foundation block of data is not accurate, the rest of your VIT program will collapse.”

What if there’s no yield mapping technology for your crop—sweet corn, silage, popcorn or hay, for example? “Aerial imagery, from aircraft or satellites, can help identify a field’s strengths and weaknesses,” Ferrie says. “Even though those images can’t tell the actual yield, they can show where differences exist.”

Scouting and your experience farming a field can be combined with aerial imagery. “You have farmed some fields long enough to know where the best and worst areas are located,” Ferrie says. “Although it’s harder to work with, this kind of information can be used to set up a VIT management program.”

Once you have a series of calibrated yield maps, comparing them will reveal more details. “Some of the most valuable maps show weather extremes,” Ferrie says. “For example, in 2012, central Illinois experienced a severe drought. In 2015, that same area was unusually wet.

“Contrasting yield maps are worth their weight in gold for telling you even more about a field’s strengths and weaknesses and planning VIT management,” he adds. “Identify areas that cranked out corn despite the drought and where the ponds, sidehill seeps and strong-yielding hilltops occurred in the wet years. These maps can tell you volumes about waterholding capacity of the soil, infiltration capacity and where drainage is poor. This knowledge will help you make better choices such as picking the best hybrid and whether to apply a seed treatment or install more tile.”

The next layer of data is soil type. “You can access soil maps online. When you layer soil maps over yield maps, you begin to see what causes variations in yield.”

Topographic maps will sharpen your focus, so you can create even more precise management zones. “They reveal where changes in elevation cause changes in yield,” Ferrie says.  

Another helpful tool to identify management zones is aerial images, captured during the growing season. They can be obtained with satellites with high resolution, manned aircraft or drones.

Once you identify management zones, and the reasons behind yield differences, you can start writing your VIT management plan. In addition to researching hybrids and population, plot a fertility program for each zone, based on regular soil tests.

“Use GPS, and continue to sample in the same zone for years to come,” Ferrie says. “Take enough samples for a good representation of the soil in each zone.” If possible, use the same lab and the same soil testing procedure (which varies among labs) every year to identify trends.

After implementing your VIT plan, monitor results and make changes as necessary. A final form of data is collected during the growing season, by scouts in the field. The farm’s pest boss and their team can gather this information while they do regular scouting for insects and diseases.

“Scouts should look for the reasons why yield falls off in certain management zones,” Ferrie says. “Did the area run out of water, or is the problem a lack of nutrients or the presence of insects or diseases?”

Scouts should check whether target populations and ear counts were achieved in every management zone. “Ear count should be within 6% of the planted population in each zone,” Ferrie says. “If it isn’t, scouts should look for the reason. If crusting or soil structure, for example, creates a history of not hitting your population and ear count goals, adjust your seed rate or management practices.

“Also verify your nutrient management plan for each management zone and hybrid. Make sure hybrids didn’t run out of nitrogen during the growing season. You might need different nitrogen programs for various hybrids and soil types.”

There’s one aspect of data collection that doesn’t involve soil or hybrids but must be considered when implementing VIT. “Various management zones will have different requirements for input application,” Ferrie says. “Look at your labor and equipment requirements from planting through harvest. Make sure you have enough people and big enough equipment—whether they come from on or off the farm [such as dealers and consultants]—to ensure timely planting, application and scouting for every management zone.

“If your plan involves adding a pass, such as a late-season nitrogen application on some zones and hybrids, study as-applied maps and actual records to make sure you have the manpower,” Ferrie adds. “Those maps and records are one more layer of data that form the foundation of your VIT plan.”


Tools are available to vary the rate of every input for every soil type in a field. Ready yourself for variable-input technology by following along with this seven-part series at bit.ly/VIT-series