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Stu Ellis, Farmgate  |   December 2, 2011 resize text

Do you have all of your nitrogen applied for next year? Have you applied just part of it?  Are you planning to apply nitrogen just in side-dress? The direction of nitrogen application technology is toward all side-dress because you will be using sensors that detect the nitrogen in the corn plant. And it is not just star wars farming, but efficiency, because the sensors call for less nitrogen than you would normally apply, and the yield turns out to be the same as if you had over-applied nitrogen before the crop was growing.

What is your current decision making process for nitrogen application? Has your rate changed in recent years? Are you applying nitrogen based on average yields? Or is your nitrogen application based on a maximum return to that resource, as recommended by the Iowa State University decision aid? Nitrogen application is not taken lightly, because of its financial boost to a valuable crop. A study published in the current Agronomy Journal details the findings of 55 on-farm tests involving crop sensors that were able to detect nitrogen levels in corn plants and adjust the rate of nitrogen being applied.

The result of the tests was to increase yield by almost 2 bushels per acre and reduce 25% of the nitrogen being applied. There seem to be some positives there.

Many researchers and farmers are beginning to have concerns about excess nitrogen being applied and making efforts that are directed toward better environmental outcomes. University of Missouri agronomist Peter Scharf says the sensor-driven nitrogen application may seem to be like a win-win, and there have not been many other systems that have actually achieved what this technology has achieved. He says optimal N rates vary substantially within a field and between fields, but most fields and most farms receive the same rate of nitrogen application, with much of the application occurring long before it is used by the corn plant. 

With higher input costs, there is more financial pressure to cut costs, and that will continue if 2012 crop prices continue to fade. Scharf’s research on nitrogen application locations in a field evolved into letting the corn plant determine if it needed nitrogen, and began using sensors to detect deficiency. Attaching sensors and flow regulators to applicators being used on farms, the results of the modified units were compared to parts of the field where sensors were not used. The nitrogen was applied between the V6 and V16 growth stages.

Across the 55 field tests an average reduction in 14 lbs of nitrogen per acre was used when the sensors were regulating the application rate. During the wet spring of 2008 the modified applicators increased the yield by an average of 8 bushels per acre.  Scharf said the sensors chose higher rates than did farmers, which compensated for nitrogen lost through the excess rain. Those results, plus the increased yield from other tests raised profit by a $17 per acre average across all farms.

So what is the downside? Scharf says the sensor system costs $10,000 to $16,000 and there is a learning curve in being able to use it. He says that is the only hurdle to wider adoption, but he also says it will take a culture change in farmers switching from fall application to a spring side-dress application of nitrogen. However, with heavy rains that either prevent the fall application or leach out nitrogen before it can be used by the corn, there is more of an incentive to apply it closer to the time it is used by the corn plant.

Summary:
A perfect world would have the corn plant use all of the nitrogen that is applied to satisfy its needs; however that is difficult to achieve. In too many cases excess nitrogen has been applied and in other cases nitrogen has been leached from the root zone before it could be used by the corn. One means of more accurate application is with the use of sensors which detect nitrogen deficiency in the corn and regulate the flow to apply the appropriate amount.  The result has been a reduction in the amount of nitrogen applied, compared to typical rates, along with no negative impact on yield.

Source: FarmGate blog

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