By Kurt Steinke and Dennis Pennington et.al
Whether you applied nitrogen before the rain or got delayed, here’s how spring timing impacts your winter wheat.
Spring 2026 is off to a wet start across Michigan with many regions experiencing repeated rainfall events, runoff and periods of standing water. Prolonged wet conditions raise important questions about nitrogen (N) management in winter wheat, particularly for fields that received early spring nitrogen applications. Understanding how nitrogen behaves in the soil—and how wet conditions interact with nitrogen form, soil temperature and crop growth stage—is essential for making sound in-season management decisions.
Field conditions, nitrogen forms and loss pathways
Nitrogen applied to winter wheat is commonly supplied as urea, urea–ammonium nitrate (UAN, 28%) or ammonium sulfate. All these fertilizers are either applied as ammonium or become ammonium in the soil. Once applied, nitrogen exists in several soil forms:
- Urea (CO(NH2)2
- Ammonium (NH4?)
- Nitrate (NO3?).
It is important to remember that all ammonium converts to nitrate, but the form present at the time of excessive rainfall may influence the risk for nitrogen loss.
UAN contains approximately 25% of its nitrogen in the nitrate form at application allowing for leaching or denitrification nitrogen losses during wet conditions. Ammonium nitrogen sources may provide some stability due to being positively charged and held on negatively soil exchange sites, but ammonium losses can still be a concern in very sandy soils due to limited cation exchange capacities.
Source : msu.edu