As harvest wraps up, many growers will turn their attention to 2024 field preparations. One of the most important decisions will be whether to apply nitrogen (N) in the fall or wait until planting.
The benefits of applying N in the fall include lessening spring workload and applying N in more favorable soil conditions.
Traditionally, fall application of N is practiced in areas where soil temperatures usually remain below 50°F from late fall to spring. Lower soil temperatures reduce the activity of nitrifying soil bacteria that convert ammonium to nitrates. However, if soil temperatures rise above 50°F, N is at risk of loss through leaching or denitrification.
Anhydrous ammonia, urea, and urea-ammonium nitrate solutions are the most commonly used nitrogen fertilizers for North American corn production. Nitrogen in ammonium form is traditionally recommended for fall applications because it is held in the soil and not subject to movement with water.
To minimize N loss, fall applications should be carefully managed.
“Growers should really pay attention to soil type,” says Mike Koenigs, Corteva Agriscience Marketing Development Specialist and member of the Corteva Nutrient Maximizer team. “Course or sandy soil cannot hold a fall application of nitrogen through the winter.”
While soil type is important to fall-applied N, utilizing nitrogen stabilizers or additives can help keep N in the soil through the winter.
Nitrogen stabilizers, like Instinct® and N-Serve®, slow the conversion from ammonium to nitrate and therefore reduce the risk of loss. Corteva Agriscience field trials conducted over several years found that the use of nitrification inhibitors increased corn yield by an average of around six bu/acre.
Because the risk of nitrogen loss is always present, growers should take precautions to reduce losses when possible. When applying fall N, selecting the appropriate nitrogen source and using a nitrogen stabilizer can help protect that investment.
Growers should consider the risk of loss for a particular field, including local climatic conditions, topography, soil type, residue level, a form of nitrogen fertilizer applied, and timing of application relative to crop growth prior to making any N decisions.