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.
He adds that some state crop asso-ciations use NDVI maps to validate their test plot results and even go so far as to throw out yield results that don’t mesh with the maps.
Along with correcting compaction problems, Rupp will use information from NDVI maps to fine-tune management zones in his fields.
Bauer anticipates the NDVI information will help Rupp make his variable-rate nitrogen applications more exact next season.
NDVI maps are also useful for analyzing drainage in a field. "Doug has tiled his fields well, but even so, he found at least one area where he’s planning to go back in and increase the amount of tile," Bauer says. "I don’t know that we would have known the field needed additional tile without the maps."
Evaluating the Payoff. The NDVI aerial imagery service costs between $2 and $4 an acre, on average. While there are no startup fees, most companies do require their customers to commit to a minimum number of acres. GeoVantage has a 2,000-acre minimum, but two or three farmers can pool their acres to reach that number.
Allied Environmental Group, based in Xenia, Ohio, is another company that provides NDVI services as part of an overall focus on precision technologies and data integration. Monsanto Company is launching its new IntelliScan program this fall on a limited basis to corn and soybean growers in the Midwest. IntelliScan provides information on field productivity levels, based on satellite imagery and aerial mapping, says Bob Starke, regional agronomy lead for the company.
Farmers interested in NDVI mapping may also want to check into technology, such as the AutoCopter, which allows growers to conduct their own field mapping. More information on this technology and equipment is available here.
Morrow says farmers who want to give the technology a try should expect a good return on their invest-ment in those fields that contain varying soil types and terrain.
"That’s where you’ll get your greatest payback," he says. "You want to pick those areas and the fields that you know you really want to improve."
Morrow also encourages farmers to work with their local seed retailer, Extension specialist or consulting agronomist to locate companies that provide NDVI mapping services. Such resources can help farmers evaluate and implement decisions based on information the maps ultimately provide.
Technology helps when Mapping out Plant Health
The Normalized Difference Vegetation Index (NDVI) is a spatial measurement that uses a combination of near-infrared and red light reflectance to assess relative vegetation biomass and vigor in fields.
Measurement results are aligned with an image file, such as an historical map, satellite image or aerial photograph. The resulting information then forms the basis for a detailed, color-coded map that visually showcases trouble areas in fields.
NDVI measurements that detect healthy vegetation in a field show up as green areas on the map. Green turns to shades of yellow and red wherever the NDVI measurements detect variations and less-than-desirable plant health. The colors used to denote plant-health variations are selected by the company providing the NDVI mapping service.
Plant-health variations result from factors including inadequate nutrient levels, poor drainage, compaction, disease and insect problems and even equipment malfunctions.
Top Producer, October 2010
- October 2010