By Tyler Kelley
Many farmers today are splitting their nitrogen (N) applications and following pre-plant N applied at lower rates with a sidedress or topdress application during the growing season. Split N applications are becoming more popular because farmers are adopting the 4Rs of Nutrient Stewardship, one of which is good timing to put down the N when the plant needs it. Applying 100 percent of N prior to planting is not optimal in most cases, says Darin Lickfeldt, Ph.D., senior technical development manager for Verdesian Life Sciences.
Lickfeldt suggests the farmers follow the best management practices for splitting your N between pre-plant applications and a topdress or sidedress application during the growing season.
- Know what your soils need. Less than ideal soils, including sandy soils, soils with lower organic matter (OM), lower cation exchange capacity (CEC) or a shallow A horizon (meaning the top soil is not deep), should apply about 50 percent of their total N in a pre-plant application and the rest with an in-season application. If farmers have close to ideal soils that hold N better with less risk of N loss, they may be able to apply up to 75 percent of their N in a pre-plant application with the rest in an in-season application.
- Time in-season application as late as your equipment allows. The later you can apply a sidedress or topdress application, the better, says Lickfeldt. For applications with a standard spray rig, the preferred timing is usually around the V6-V8 stage before the canopy closes. If you try to apply when the corn is taller, it would require a high-boy rig to apply the N to avoid damaging stalks.
- Do not apply in wet conditions. Applying in-season N in wet conditions can lead to soil compaction.
- Consider sidedress application to put N where the plant needs it most and avoid risking injury to the crop. One challenge with a topdress application broadcast over the top of the crop is that some of the fertilizer 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 farmers sidedress the N application between rows. “One of the 4Rs of Nutrient Stewardship is applying the 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 sidedress to avoid injury to the crop. There are also new technologies that can apply N directly on or very near the corn row rather than on the center.”
- Protect your N from loss. Because the weather is very unpredictable, farmers should take steps to protect their applied N from loss to the environment. If it ends up being dry, farmers could lose their applied N to volatilization; if it ends up wet, you could lose N to denitrification; and if you have water moving through the soil, you could lose N to leaching. Farmers need to make sure to follow the 4Rs of Nutrient Stewardship and apply the right product at the right time at the right rate and in the right place to minimize N loss. But sometimes even when farmers follow the 4Rs, conditions can sometimes be conducive to lose N to the environment. NutriSphere-N® Nitrogen Fertilizer Manager helps protect applied N from all three forms of N loss, giving you insurance 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 on granular urea, liquid UAN and anhydrous ammonia.
- Following the application, monitor the results. Monitoring results allows farmers to adjust their technique to avoid injury or possibly mirror successful techniques with variable rate applications the following year.
Following these best management practices will help farmers realized both economic and environmental benefits by ensuring more of their applied N is taken up by the plant and less is available to be lost to the environment. For more information on the 4Rs Nutrient Stewardship, visit http://www.nutrientstewardship.com/4rs. For more information on NutriSphere-N and other products from Verdesian Life Sciences, visit www.vlsci.com.