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Implementing optical sensing requires growers to think differently about the application process,as well as potential benefits. Minnesota farmer Robert Goettl emphasizes not simply relying on the technology. “Every year the vegetation is different, and even different varieties can have different color changes,” he says. “You need to think about what the corn looks like before you even start. You also have to match the soil type.
“If the corn is really dark, you may think you have plenty of N, but the variability will still be there,” he says. “If you set parameters and the system doesn’t want to apply any N, you need to adjust it by altering growing degree days, N use efficiency or NDVI (Normalized Difference Vegetation Index) on the controls.”
Applicator equipped GreenSeeker optical sensors use N-rich strips to variable-rate apply liquid N in-season. Robert, Jerome and Justin Goettl rely on a coulter-cart system similar to this one to boost yields with fewer gallons of liquid N.
In-crop optical sensing, also called canopy sensing, is boosting yields and cutting costs for Robert Goettl, his brother Jerome and nephew Justin. Their GreenSeeker crop sensing system allowed the Le Center, Minn., farmers to shift away from reliance on all fall nitrogen (N) application. For the past four years they have combined a base fall rate with variable in-season applications using a coulter cart. Yields were up 10 bu./acre or more in the drier-than-normal 2012 season.
“We like to try for a base of 130 lbs. of nitrogen and then top off with the in-season liquid,” says Robert. “In the past we might have put on 200 lbs. of N, but not get 200 bu. of corn. With the GreenSeeker system, it is almost a one-to-one relationship.”
Micah Eidem, GreenSeeker market manager for Trimble, suggests adoption of optical sensing is finally pushing past early adopters. It has been two decades since GreenSeeker first hit the market, with OptRx from Ag Leader and CropSpec from TopCon being introduced more recently. Reaching this tipping point hasn’t been easy. Even the terminology, such as NDVI (Normalized Difference Vegetation Index) sensing, can be challenging. Add to that the technical differences in how the sensors work.
“Educating potential users is the biggest challenge,” says Eidem. “The university guys understand what the technology does and that there is solid data behind it. Research continues to come back positive, and now the growers are starting to understand it, as well.”