Field agronomist Missy Bauer and Doug Rupp evaluate how NDVI field mapping alerted them to soil fertility needs and disease and pest pressure.
Doug Rupp stares intently at a sheet of printer paper in his hand. The paper shows details of one of his best corn fields, awash in varying shades of green. Red lines that look out of place zigzag back and forth across the page. Rupp says the lines indicate pinch-row compaction problems caused by his center-fill planter last spring.
"We could see the wheel tracks in every field, even on our heavier ground, because they showed up red on the map," Rupp says. "Without the map, we wouldn’t have known there was a problem."
The map Rupp references is the result of remotely sensed imagery, a type of high-tech aerial photograph of his fields based on the Normalized Difference Vegetation Index (NDVI). (See sidebar below for more information.)
"NDVI imagery gives us a really accurate layer of spatial information that we can use to help Doug and other farmers fine-tune their management and agronomic practices," says Missy Bauer, Farm Journal associate field agronomist.
Bauer is one of Rupp’s advisers for the 2010 Ultimate Farm Quest program. The program is designed to help Rupp take his northwest Ohio operation to a higher level. Top Producer will be reporting on his experiences with the program throughout the coming year.
The accuracy of NDVI-based maps is significant, Bauer says. Such maps show information on a meter-by-meter basis as opposed to a yield map, which provides data based on a 20' to 35' swath, depending on the combine header used.
That accuracy is good news for Rupp, Bauer says, because now he knows he needs to make adjustments to his planting practices next spring. Bauer adds that corn rows affected by pinch-row compaction yield an average 7 bu. to 10 bu. per acre less than unaffected rows.
Set Some Goals. Two of the best times to implement the NDVI aerial mapping process are just prior to tasselling or just before drydown, says Nicholas Morrow, a field representative for GeoVantage, Inc., which provides NDVI mapping services. Morrow is based in Fort Collins, Colo.
"When you implement it depends on what you want to achieve," Morrow says. "There are hundreds of uses for this technology."
Bauer says that when NDVI mapping is done early in-season, farmers can see and correct some problems in corn such as insufficient nitrogen levels. Along those same lines, Morrow adds that NDVI mapping after canopy closure supports what he calls guided scouting.
"You can get a lot more acres scouted in a day, because the imagery tells you those areas that need your attention and those that don’t," he says.
At harvest, NDVI mapping provides information that correlates closely to yield maps. Morrow says the maps help verify what farmers see from their combine and on their yield monitors.
- October 2010