Mike Olson explains how the OptRx sensors measure the health of plants by using the reflectance of light shined on growing plants during the “Where Technology Meets Dirt” Road Tour. The information provides farmers the opportunity to sidedress various rates of nitrogen based on the needs of the plants, helping to improve the efficient use of nitrogen.
Mike Olson explains how the OptRx sensors measure the health of plants by using the reflectance of light shined on growing plants during the “Where Technology Meets Dirt” Road Tour. The information provides farmers the opportunity to sidedress various rates of nitrogen based on the needs of the plants, helping to improve the efficient use of nitrogen.
GOODFIELD, Ill. — Managing nitrogen should be the concern of every farmer.

“You may do what’s good for your farm in terms of nitrogen management, but you should be concerned about what your neighbors are doing and what farmers are doing 10 counties from your farm,” said Rachel Halbach, agronomist with Hagie Manufacturing Co. “Because eventually regulation is probably going to be part of what you have to base the programs around.”

There are several different forms of nitrogen, including urea, ammonia, nitrates, nitrites and ammonium, Halbach said during the “Where Technology Meets Dirt” Road Tour.

“We are most concerned with nitrates because they move the most rapidly, and corn likes to take up and utilize nitrates,” she added.

Nitrates dissolve in water, and when water moves through soil, the nitrates move, too.

“The nitrates may move out of the root zone of the corn, to the ground water, to the creek and so forth,” Halbach said. “We like nitrates, but they’re also our enemy because we can’t keep them where we need them.”

Why Nitrogen?

There are several reasons to apply nitrogen to corn.

“Nitrogen is very important for nutrient uptake,” Halbach explained. “When there is nitrogen deficiency, that inhibits the plant from getting the rest of the nutrients it needs.”

Nitrogen impacts cell division and growth, and this really comes into play in the fall, the agronomist said.

“If we have a nitrogen-deficient plant at the time of grain fill, the plant will take the nitrogen out of the cells in the stalk and put it into the grain,” she said. “That may mean lodging and standability issues in the fall.”

Leaching is one way nitrogen is lost.

“In a year with average rainfall, you will loose 15 to 50 pounds of nitrogen naturally due to leaching,” Halbach said. “It takes one pound of nitrogen to produce one bushel of corn, so that’s 50 bushels of corn.”

Denitrification occurs in saturated soils and areas of the field with standing water.

“The bacteria changes nitrates into gases, and the nitrogen goes up into the atmosphere,” the agronomist said. “Within three days, you can lose 10 percent of the nitrates and every day on top of that another 10 percent.”

Halbach noted the importance to match the application of nitrogen with the uptake of the plant to reduce the risk for loss.

“At V12, the plant has only used 40 percent of the total nitrogen for the season,” she said. “The highest rainfall amounts are in April, May and June, which are the highest risks for loss of nitrogen and corn isn’t taking up nitrogen very quickly during this time.”

Nitrogen management will change from year to year because of different weather conditions, Halbach said.

“We can become more efficient by spoon-feeding or sidedressing nitrogen multiple times, and that takes time and more intensive management,” she said. “But we’re reducing the risk for loss because we’re putting smaller amounts on when the crop is able to take it up.”

The ability to apply nitrogen to the corn crop at the appropriate time can be a challenge for farmers. If you don’t have a tool bar and you rely on your local retailer to rent equipment, you may be the first or the last on the list, Halbach said.

“And if you didn’t pre-pay or you have an unplanned nitrogen application, the costs could be higher,” she said.

Sensor Option

One option for farmers to use to evaluate the health of their crops is the OptRx crop sensor.

“OptRx is short for optimum prescription, and the sensor is mounted on a tool bar or sprayer to measure the crop health as you go through the field,” explained Mike Olson, with Ag Leader Technology.

The OptRx sensor determines a vegetative index that includes the biomass and health of the crop, Olson said.

“We can apply nitrogen based on the health of the crop,” he said. “In areas that are struggling, we put more nitrogen down.”

Olson stressed that the sensors are not a silver bullet.

“If your P and K levels aren’t right, the sensors will detect the stress and nitrogen will be put down, but there could be other issues,” he noted.

“We ran the sensors across the field at V5 stage, and we can pretty much predict the yields,” he said. “The losses and stresses at V5 carried all the way through to harvest, so that gives us an opportunity to improve that situation by hitting the crop with sidedressing nitrogen.”

Ag Leader recommends using the OptRx sensors when the corn crop is at the V5 stage or about one-foot tall.

“That’s when we have enough canopy to be able to measure the crop and to be able to see what it’s doing,” Olson explained. “Prior to V5, we get a lot of dirt and background noise in the sensor data.”

The operator of the applicator has total control of the amount of nitrogen applied in a field.

“You are in charge,” Olson stressed. “You can enter a minimum rate and a maximum rate you want to apply.”

Calibrating the OptRx sensor is important just like any other sensor system.

“You can calibrate the sensors anywhere in the field, so go to a good part of the field and base your calibration off that part of the field,” Olson advised.

“As long as the different hybrids have similar characteristics like the same maturity rates and planted in a similar timeframe so they are in the same growth stage, you don’t have to do different calibrations for different hybrids,” he said.

However, Olson added, if the corn is in different growth stages, recalibration will be necessary.

“A three-sensor system from Ag Leader will run about $11,000, but don’t let the price scare you,” he said. “With $20 per acre more profit, it only takes 525 acres to pay for the sensors, so you can pay for them pretty quickly.”

For more information about Ag Leader Technology, see www.agleader.com.