SPRINGFIELD, Ill. — The Illinois Nutrient Research and Education Council (NREC) offers recommendations for Best Management Practices (BMPs) based upon nine years of NREC-funded research. The research was conducted (and will continue to be conducted) on actual farmers’ tile-drained fields.
“Tile-drained fields are essential in the research because tile load has been identified as the primary source of nutrient loss to the waterways and environment,” said Julie Hewitt, NREC’s Executive Director.
The following BMPs follow both the Illinois Nutrient Loss Reduction Strategy (INLRS) and the University of Illinois researchers’ recommendations: The BMPs include:
1. Use the Right Nitrogen Rate and do not apply the full rate in the fall. NREC recommends saving 30-40% of the rate to be applied next year’s pre-plant or side-dress. This helps to manage both environmental and agronomic risk since farmers will not know what the weather will be over the next six months. The Illinois Nitrogen Rate Calculator is updated each year with the results of dozens of nitrogen rate trials performed throughout the State. The current recommended rates for corn following soybean are:
- Northern Illinois: 171 – 194 lbs. per acre
- Central Illinois: 181 – 200 lbs. per acre
- Southern Illinois: 200 – 225 lbs. per acre; nitrogen should not be fall-applied in southern Illinois.
2. Wait until mid-day soil temperatures in bare soil at the 4″ depth is 50 degrees and the weather forecast indicates temperatures will not rebound, but rather will continue to cool. While the Illinois Fertilizer and Chemical Association (IFCA) will post the State Water Survey soil temperature each day, it is recommended growers take the soil temperature themselves.
3. Use a USEPA labeled nitrification inhibitor with all fall-applied ammonia (N-Serv and Centuro). These products are registered as pesticides because they inhibit bacterial activity that can convert ammonium to nitrate. These bacteria are active until the soil freezes. The inhibitor is intended to provide protection against nitrification in the late fall, early winter, and spring. Protecting ammonia with a nitrification inhibitor helps but is less effective if soils remain warm.
According to NREC’s Research Manager, Dr. Shani Golovay, “There is a lot of anxiety around nitrogen cost and availability, so farmers are tempted to get that fall nitrogen in the ground even if the soil temperature is a little too warm. However, even with the inhibitor, nitrogen is lost to nitrification and loses money for the farmers when soil remain at 500 or above. It is only when soil temperatures are at freezing that the nitrification process stops and keeps the nitrogen in place until spring.”
Lowell Gentry from the University of Illinois adds that “timing of fertilizer N is important in that fall N is definitely leakier and that 7-percent of fall fertilizer N lost to tile accounts for more than 30-percent of the tile load.” Gentry further suggests that in a warm winter and spring, farmers need to include a cover crop in their production strategy.
NREC-funded research shows that there is no yield penalty for applying N in the fall, but there is a water quality penalty especially in tile-drained fields. NREC research shows that fall applied N loses up to 12 lbs. more per acre than N applied in the spring.
NREC publishes research results on its web site at www.illinoisnrec.org.
The Illinois Nutrient Research & Education Council (NREC) was created by state statute in 2012. Funded by a 75-cent per ton assessment on bulk fertilizer sold in Illinois, NREC provides financial support for nutrient research and education programs to ensure the discovery and adoption of practices that address environmental concerns, optimize nutrient use efficiency, and ensure soil fertility. A 13-member NREC Council annually solicits, reviews and funds projects that fulfill the organization’s mission.
— Illinois Nutrient Research & Education Council