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GreenSeeker Matches Nitrogen to Crop Needs

By Susanne Retka Schill | September 08, 2008
Remote sensing technology initially developed for satellite imagery is being applied on the ground to fine-tune fertilizer applications. GreenSeeker sensors developed by NTech Industries Inc. in Ukiah, Calif., in cooperation with Oklahoma State University, use optical sensors that emit and capture red and near-infrared light to sense crop vigor. The GreenSeeker sensors are mounted on a fertilizer applicator and coupled to the equipment's variable rate applicators.

NTech Chief Operating Officer Ted Mayfield explains that in corn, the amount of nitrogen available from natural sources such as mineralization or rainfall can vary widely from year to year. Looking at university nitrogen response trials, there are growing seasons when crop yields on plots with no applied nitrogen equal plots with high levels of nitrogen.

GreenSeeker aims to capitalize on that phenomena. "Getting the rate right for this year is a huge component that GreenSeeker is trying to accomplish," Mayfield says. In addition, the sensors identify crop variability. "This part of the field isn't doing very well," he says as an example. "Let's not waste nitrogen on it. This part of the field looks pretty darn good, but not as good as the reference strip. That's where we're going to get a good economic return on added nitrogen."

When planting a field, a farmer applies a high rate of nitrogen on a calibration strip that is generally the width of the applicator to be used for topdressing. The rest of the field gets enough nitrogen to get the crop off to a good start, but well below the optimal level. "Say the farmer generally puts on 150 pounds of nitrogen per acre," Mayfield says. "He will apply 75 to 80 pounds on the whole field, and on a reference strip, he puts down 180 pounds." When the corn crop is between the eight- and 12-leaf stage, the farmer goes out with the GreenSeeker sensors mounted on his applicator and calibrates the equipment against the strip that received the high nitrogen rate. Then, the rig is run over the entire field, applying a variable rate of nitrogen based on the sensors' readings. "We're going to pick up areas of the field where there are less healthy plants or thin stands, and less nitrogen will be applied in those areas," he says. An example would be areas with stunted plants that flooded during the season.

Mayfield says with high fertilizer prices, interest in the technology is increasing from the handful of producers who tried it when GreenSeeker was introduced four years ago. "Nitrogen is 25 (percent) to 35 percent of the cost of production in raising corn," he says. Costing approximately $22,000, the system has given a payback in the first year in some cases, he adds, and it's expected to return the investment in two years in fertilizer cost-savings.

The GreenSeeker sensors can be added to a variety of equipment. Some producers mount the sensors on the toolbars of nitrogen side-dressers. Others mount the sensors on high-clearance spray rigs that have been fitted with drop nozzles to dribble the additional nitrogen between the rows. GreenSeeker can be used with liquid, dry or anhydrous formulations, and is compatible with existing rate controllers. "It's all about trying to make the grower more efficient," Mayfield says. "We're trying to maximize the return they get on the money invested in nitrogen. The great thing is that it's good for the environment, too, because if you only put on the nitrogen that the plant is going to uptake, then it's not going to get out into the environment."