Splitting N Applications Improves Efficiency

Proper management of split applications provides nitrogen when plants need it most

Published online: Apr 19, 2017 Fertilizer, New Products
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Many growers looking to improve their nitrogen efficiency and their nutrient stewardship are turning to splitting their nitrogen applications and following pre-plant nitrogen applications at lower rates with a side-dress or top-dress application during the growing season.

“More farmers are adopting the 4Rs of nutrient stewardship, which includes good timing to put the nitrogen down when the plant needs it,” says Darin Lickfeldt, senior technical development manager for Verdesian Life Sciences. “Applying 100 percent of nitrogen prior to planting is not optimal in most cases, so split nitrogen applications are becoming more popular.”

Growers in the Midwest, Northeast and North-Central states interested in splitting their nitrogen applications should follow some best practices, including knowing what their respective, individual soil types need. Less than ideal soils, including sandy soils, soils with lower organic matter, lower cation exchange capacity, or a shallow A horizon (meaning the topsoil is not deep) should apply about 50 percent of their total nitrogen in a pre-plant application and the rest with an in-season application, Lickfeldt says. If growers have close to ideal soils that hold nitrgoen better with less risk of nitrogen loss, they may be able to apply up to 75 percent of their nitrogen in a pre-plant application, with the rest done in an in-season application.

Timing in-season applications is another factor to consider. Lickfeldt says the later growers can apply a side-dress or top-dress application, the better. For applications with a standard spray rig, the preferred timing is usually around the V6 to V8 growth stages for corn, before the canopy closes. If growers try to apply when the corn is taller, it would require a high-clearance sprayer to apply the nitrogen to avoid damaging stalks. 

Growers are cautioned to avoid applying nitrogen in wet conditions, which can lead to soil compaction. Another concern is that nitrogen applied under wet conditions is more susceptible to loss to the environment.

Another consideration when splitting nitrogen applications is minimizing risk of crop injury. One challenge with a top-dress application broadcast over the top of the crop is that some of the fertilizer granules could get caught in the whorl, which can cause injury to the crop. At those vegetative stages, any injury to the crop will hurt your yield, says Lickfeldt. That’s why a lot of growers side-dress the nitrogen application between rows.

“One of the 4Rs of nutrient stewardship is applying fertilizer at the right place, and it makes a lot more sense to place it right next to the corn plant rather than having a portion get caught in the whorl,” says Lickfeldt. “One trend is using a urea ammonium nitrate (UAN) liquid as a side-dress to avoid injury to the crop. There are also new technologies that can apply nitrogen directly on, or very near, the corn row rather than on the center.”

Following the 4Rs of nutrient stewardship and best management practices for nitrogen applications are critical, but conditions can still be conducive to nitrogen loss to the environment. Because weather is unpredictable and nitrogen lost to the environment does not help the crop, growers should protect their nitrogen when possible.

NutriSphere-N Nitrogen Fertilizer Manager helps protect applied nitrogen from being lost to the environment via volatilization, leaching and denitrification, so farmers can be confident they won’t lose applied nitrogen, regardless of what the weather may be,” says Lickfeldt. “Over 500 trials have been conducted on NutriSphere-N use on corn and have shown more than a 90 percent positive yield response over the control. NutriSphere-N has been commercialized for more than 10 years and has been used on more than 46 million acres. NutriSphere-N has formulations that can be used with granular urea, liquid UAN and anhydrous ammonia.”

The last tip to make the most out of split nitrogen applications is to monitor the results. This will allow growers to adjust their technique to avoid injury or possibly mirror successful results with variable-rate applications the following year.

Following these best management practices will help growers realize both economic and environmental benefits by ensuring the plant takes more of their applied nitrogen up and less is available to be lost to the environment.