Rain and wet weather has inundated the Upper Midwest recently, from South Dakota to Minnesota and on. Because of all the moisture, South Dakota State University Extension Soil Specialist Ron Gelderman says some fields may experience nitrogen (N) loss. Whether N leaching has occurred depends on many factors, he says.
"There are many considerations including: soil type, amount of rainfall, rainfall intensity, when N was applied, nitrification inhibitors used, organic matter levels and many more," Gelderman says.
Two modes of nitrogen loss
With heavy rains, Gelderman says the two primary modes for N loss include leaching – where nitrate-N can be moved down in the soil profile and sometimes out of the root zone (4-5 ft.). Denitrification is the other mode of N loss. Denitrification is where nitrate can be biologically converted to gaseous nitrogen forms and lost to the atmosphere.
"With present soil temperatures in the low to mid-60s, N fertilizer should mostly have converted to nitrate by now," Gelderman says. "It usually takes urea two to four weeks to convert to nitrate depending on temperatures. So we can assume normal spring N applications were susceptible to both leaching and denitrification."