On a plain, 8½"x11" sheet of white paper, red, green and yellow streaks reveal the rows where Leon Knirk’s corn fields had adequate nitrogen this year and, likewise, where they didn’t.
“We could even tell where my dad had buried the foundation of an old building at one time, because it showed up red on the map,” says Knirk, who farms and runs a cattle business with his wife, Jennifer, near Quincy in south-central Michigan.
The map Knirk references resulted from remotely sensed imagery of his fields, a type of high-tech aerial photograph based on Normalized Difference Vegetation Index (or NDVI; see sidebar for more information).
“NDVI imagery gives us a really accurate layer of spatial information that we can use to help Leon and other farmers fine-tune their management and agronomic practices,” explains Missy Bauer, Farm Journal Associate Field Agronomist.
Bauer is one of Knirk’s advisers for the 2010 Ultimate Farm Quest program. The program is designed to help Knirk take his operation to a higher level of performance. Farm Journal will report on his experiences with the program throughout the coming year.
The accuracy of the map is significant, Bauer says. NDVI maps show information on a meter-by-meter basis as opposed to yield maps, which provide data based on a 20' to 35' swath, depending on the width of the combine header that is used.
Timing is important. Two of the best times to implement the aerial mapping process are just prior to tasselling and just before drydown, says Nicholas Morrow, a field representative for GeoVantage, Inc., based in Swampscott, Mass. The company provides NDVI imagery mapping services.
“When you implement it depends on what you want to achieve,” he says. “There are literally hundreds of uses for this technology.”
Bauer says that when NDVI mapping is executed early in the season, farmers can see and correct certain problems such as insufficient nitrogen levels in corn.
Along the same lines, Morrow adds that NDVI mapping after canopy closure supports what he calls guided crop scouting.
“You can get a lot more acres scouted in a day, because the imagery tells you the 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 technology helps to verify what farmers are seeing from their combine and on their yield monitors.
In addition, he adds that some state corn and soybean associations use NDVI maps to validate their test plot results and even go so far as to throw out yield results that don’t mesh
- October 2010