Before yield monitors, farmers knew where to find the best- and worst-yielding areas of each field. After yield monitors came along, farmers knew the yield from pass to pass, but didn’t have a map of yield variation.
“Now, GPS lets us make maps, so we can study layers of data to discover what’s happening in every part of the field,” says Farm Journal Field Agronomist Ken Ferrie. “It’s like the difference between looking at an oil painting and a photograph. We can even see beneath the surface.”
Here are some tips to help you translate your data into higher yield and ROI:
1. Start with accurate yield maps.
“Only half of our new customers have good spatial yield maps,” Ferrie says. “The rest are accurate to scale tickets, but don’t give good details of the field. A good spatial map with accurate data points — not one that has been ‘krieged’ or interpolated to create zones — will talk to you. Once you see one, you’ll want to make one every year, and use years (layers) of data to improve yield and ROI.”
When combine operators know the importance of good maps, he says, they will create accurate ones.
2. Solve mysteries by adding layers of data.
Soil-type maps and topography maps (called LIDAR, for Light Detection and Ranging) are key information sources.
“GPS soil-type maps are free on the internet,” Ferrie says. “Laying one over an accurate, spatial yield map instantly adjusts your focus.
You can collect topography maps from equipment in the field or get them from the internet. While these maps are still somewhat coarsely focused, they can explain a lot of yield swings.”
Ferrie and his team have used LIDAR maps to fix many surface drainage issues. He says: “Sometimes you need to remove only 3" or 4" of soil to cut a ditch to a wet pocket, and you see the effect the next year.”
3. Let yield, soil and topography maps guide your soil test.
“Soil test zones should represent how a field yields,” Ferrie says. “When you collect samples, try not to mix low- and high-yielding areas or silt loams and sand loams.” This information can guide you into variable-rate fertilizer application, making you an effective steward while boosting your profits.
4. Decide what you can fix.
“Fertility is still a somewhat coarse adjustment, suitable for treating larger areas such as sand knobs and hilltops.” Ferrie says. “We can focus on very small zones, but if our applicator spreads a 90'- or 120'-swath and a zone is only 50' across, it’s too small to fix. But technology will soon provide the tools to do this.”
On the other hand, he says, you can vary plant population and hybrid or variety by row and by foot of row, to treat small areas such as sand lenses and gravel veins running at an angle across the field but only 50' wide. Then you can hit areas with lower population and defensive hybrids.
Some technology can map soil properties deeper than a standard soil test can read. “We can pinpoint subsoil features such as sand lenses and depth horizons that explain issues invisible to the eye but visible in a yield map,” Ferrie says.
5. What data do you need?
That depends on what you will use it for. “Aerial photos and NDVI (Normalized Difference Vegetation Index) images can reveal differences in the crop throughout a field,” Ferrie says. “Some of the free satellite photos available on the internet are of low resolution, very coarse and cheap, while photos taken from a plane or drone are higher resolution, but also more expensive. Aerial images can be as high resolution as you want to pay for, so decide what quality you need, and ask what resolution your images will be — for example, 5 m x 5 m or 1’x1' — before you commit.”
Each image shows only one moment in time, Ferrie says. So you might want to take multiple images through the season to avoid missing something.
“Elevation data can be collected from a combine, and LIDAR topography maps, which are much higher resolution, are free from the internet. Both types of data can help us decide where to put drainage, although neither is accurate enough to guide a tile plow,” he says.
Soil data can be obtained with electroconductivity mapping, which involves running coulters through the soil, or by swath mapping, in which a sled is pulled over the surface. But don’t sacrifice accuracy by running a mapper at wide intervals and “krieging” the data to make a map, Ferrie warns. You also can outfit your planter to map soil temperature, conductivity, moisture at seed depth and organic matter as you plant.
6. How to use your data.
“Look for zones tied to perennial yield swings on your yield map,” Ferrie says. “Aerial images will reveal both perennial yield swings, which you may be able to fix, and annual issues such as spray drift or overlapping spray from a neighbor’s field, which you just need to know about.”
If high-resolution images show repeated yield drops that layers of ground data can’t identify, Ferrie suggests taking a closer look. Soil tests, tissue tests and parasite tests in those areas can help identify the problem.
”If it isn’t fixable, adjust your yield goal and variable rate your fertilizer, population and pesticides,” he says.
Your goal is to get repeatable data with good resolution, Ferrie says. Then, use it to plan changes. Problem areas too small to remedy now will become fixable as technology develops, if you have the right data.
SWAT Maps (Soil, Water and Topography)
- Soil texture, organic matter and topsoil depth can impact yield and fertilizer response.
- Water has the biggest influence on yield and fertilizer response.
- Topography can influence soil moisture, erosion, organic matter levels, pH, and soil fertility levels.
Mark Your Calendar
Join Ken Ferrie and team for the 2023 Farm Journal Corn and Soybean College.
July 25 - 26
Heyworth, Ill.
