farmgate: Supplemental Nitrogen: How Do You Avoid Wasting Money Where It Is Not Needed?
Across the Eastern Cornbelt about all of the corn that is going to be planted has been planted. Corn specialists, such as Bob Nielsen at Purdue, are recommending that corn planters be parked because of the doubt that exists for the economic and agronomic viability of any unplanted corn. But even though getting corn planted has been a major challenge for thousands of farmers, what about the issue of nitrogen?
The late harvest of 2008 caused many farmers to run out of time before they could get any fall plow down nitrogen on their 2009 cornfields, then came the wet spring this year that prevented spring nitrogen application for many farmers. In the meantime, the value of the nitrogen was lost to millions of acres of corn because it dissipated while corn planters were kept out of the field by incessant rain. So, what is the solution? MO Extension agronomist Peter Scharf says the solution is sensor-guided sidedressing. In a nutshell, nitrogen is applied between corn rows with the appropriate volume determined by a tractor mounted sensor which determines the color of the corn leaves. If an area of the field has sufficient nitrogen the leaves will be a deeper green and the controller reduces the volume flowing to the applicator. A corn grower will save money by not applying nitrogen where there is a sufficient amount.
Scharf says University of Missouri experiments last year found that corn that was side dressed with nitrogen out yielded that with pre-plant nitrogen application by 44 bu. per acre. And he says with the warm soils and continuous rainfall, much of the pre-plant nitrogen for the 2009 corn crop may have leached out. With soil and ponding variations in a given field, Scharf says the nitrogen available to the new crop could be widely variable and late planted corn may not be capable of rapid uptake until July, with additional losses of nitrogen expected.
Scharf reports on field trials in a variety of areas with different types of nitrogen used, but noting great variations in corn color attributed to nitrogen availability. He says cooperators are impressed to see the flow of nitrogen reduced when the sensors tell the controller that sufficient nitrogen exists, and the flow increased when the applicator moves into an area where the corn is more yellow than dark green. Scharf says the process is not good for adding just 30 additional pounds per acre, but is very good at determining whether the area of the field needs “a little, a medium amount or a lot.”
One issue that Scharf says needs to be addressed is the need for high variations in pressure, both for liquid nitrogen and anhydrous ammonia. But he says new nozzle technology has allowed a four-fold pressure increase. Without that, your equipment may only allow a doubling of the pressure between the bottom and top rates of application. He says changing the rate for a dry application only requires speeding up the delivery belt and spinners.
The optimum rate of nitrogen application is based on green reference points in the corn, but those can be highly variable themselves. Scharf says one problem occurred in the sensors detecting a specific need late one day in a field and a different need for nitrogen the next morning, although there was little difference in the corn. He says that problem could have been solved with a recalibration of the equipment the second day, which would have accounted for the heavy dew that threw off the sensors from where they should have been. He says the problem can be resolved with frequent recalibrations.
Scharf says a constant field standard can be set with a heavy application of nitrogen across the direction of the rows before the field is planted. At that point the equipment has a top end to for constant recalibration every time the equipment passes over the strip.
Another issue is how many of the sensors are needed, which can be a significant cost. Scharf says he believes three reaches the point of diminishing returns, although some suppliers sell them in packages of four and six. His newsletter article addresses several different suppliers of the technology and his viewpoints on their values.
Summary:
Delayed corn planting also allowed preplant forms of nitrogen to dissipate, leaving some fields with wide variations in their need for supplemental nitrogen applications. One potential solution is tractor-mounted sensors which detected the greenness of the corn which reveals whether it has sufficient nitrogen or needs additional side-dress application. Such a process may require a capital outlay for the sensors and the controller, however may result in significant savings in not having to apply nitrogen where sufficient supplies already exist.
Posted by Stu Ellis on June 22, 2009 12:44 AM to farmgate