Questions on Fall Nitrogen
This time of year with the milder than usual weather conditions minds tend to ponder the status of fall applied ammonia.
Taking a look at one of United Prairie’s weather stations near Camargo, Illinois, it is safe to say we are well on our way to recharging soil moisture with 6+ inches of rain accumulated since mid-November. The graph below created from our Data on Touch™ platform shows each of the rainfall events (blue line) along with both ambient air temperatures (gold line) and the soil temperature at the 5 inch level (orange line). The temperature scale is located on the left-hand side and the rainfall scale is on the right side.
With all this rain, is my nitrogen disappearing? For most of us, the source of nitrogen applied this fall was anhydrous ammonia (NH3) and a large percentage of those tons were treated with a nitrogen stabilizer. When applied to soils, NH3 quickly bonds with water, to become ammonium (NH4+). In this form it binds tightly with soil particles (- negatively charged) and will not leach. What can and eventually will change this tight bond is nitrification which is a biological process that converts NH4+ to the leachable nitrate (NO3-). The biological activity responsible for this conversion is slowed considerably at soil temperatures of 50° F and lower, which is why fall applied ammonia applications are delayed until average soil temperatures fall into this range.
Another look at the graph and you will note spikes of soil temperatures (orange line) at the 5” depth above 50° F on several occasions. Is this cause for alarm? And what about the stabilizer I applied with the NH3? First, nitrification does not stop at 50° F. It is slowed considerably at that temperature and lower. Stabilizers such as N-Serve® will slow that conversion process even more. Brief spikes in soil temperature should have little impact on fall nitrogen loss particularly if NH3 was applied later in the fall as experienced this year.
Early springtime weather tends to be a more important indicator to help determine the possibility of fall N application loss. With soil moistures high now, there is a potential for excessively wet soil conditions next spring when soil temperatures are on the rise. With 27 installed weather stations operating in the United Prairie region today, we look forward to begin assessing the state of soil applied nitrogen for our customers. **Plan now to attend our Winter Grower Seminar on January 5 at the IHotel in Champaign to learn more about our new developments and trial results from 2015.