If it isn't one thing, it's another. That's what many farmers may be thinking after the drought decimated crops last summer and rainy weather – in some cases significant flooding – came calling just a few months later.
That's why Fabian Fernandez, a nutrient management extension specialist in the Department of Crop Sciences at the University of Illinois, said evaluating your N will be more important than ever this growing season.
Fernandez explained that most of the fall-applied nitrogen is either ammonium (NH4+) or a form that transforms rapidly into ammonium. The conversion of ammonium to nitrate (NO3-), or nitrification, is a bacteria-mediated transformation.
This means that the amount of nitrification that occurs in the soil is dependent on soil temperatures and the amount of time between application and when the soil is saturated with water.
So, while wet soil conditions this spring may be a reason for concern that last fall's nitrogen has been lost, cold temperatures that followed the rain might have substantially reduced nitrification, Fernandez said. But, he added that warming temperatures will boost nitrification.
"When nitrate is present and soils warm up, nitrogen loss will start under saturated water conditions mostly through denitrification in fine-textured soils and through leaching in coarse-textured soils or intensively drained soils," he said.
Fernandez pointed out that an important aspect to keep in mind is that the portion of the applied nitrogen that is in nitrate form is only subject to denitrification or leaching. However, just because nitrogen is in the nitrate form does not mean that nitrogen is lost; it simply means that it is susceptible to loss.
After determining how much of the nitrogen is in the nitrate form, Fernandez said it is possible to estimate how much nitrogen is potentially lost through denitrification based on 4-inch soil temperature and the number of days the soil has been saturated.
If leaching is a greater concern than denitrification, for each inch of precipitation, nitrate moves approximately 5 to 6 inches in silt loam and clay loam soils and approximately 12 inches in coarser textured-soils, he said.
"This year an important concern is the potential for loss of the carryover nitrogen for fields going back to corn this year," Fernandez said. "Some fields had substantial amounts of nitrogen after last growing season. Most of this nitrogen was in the nitrate form, thus the potential for loss by leaching since last fall was not related to temperature, but by the amount of excess precipitation.