Considerations Of Applying Nutrients To Frozen Ground

PRINCETON, KY.
   Some producers are taking advantage of frozen ground conditions to apply nitrogen to wheat fields or manure to corn fields. While this practice reduces the risk of compaction or rutting of fields, there are other factors to consider. When nutrient applications are made to frozen ground, one must consider what happens during rainfall events when the ground is still frozen or saturated. When the soil is frozen or saturated, water is not able to infiltrate into the soil profile and the water and accompanying nutrients can runoff to adjoining properties or waterways.
   NRCS Code 590, as well as conditions set forth in many environmental permits, prohibits the application of manure to frozen ground for this reason. While it is true that producers not participating in NRCS nutrient management programs are not obligated to follow NRCS Code 590 guidelines, the science behind these recommendations are solid. If a light rain occurs over an extended period of time, then the risk for runoff is small to frozen ground.  However, if a heavy or intense rainfall occurs, the risk for runoff is considerably greater.
   On January 30th, the depth of frozen soil was measured at Princeton, KY on a Zanesville silt loam soil and a Pembroke silt loam soil. Soil was frozen to a depth of 6 to 9 inches and no “thawed ground” was observed even though air temperatures were above 32 degrees Fahrenheit. When the ground is frozen to these depths, it will take several days for the ground to thaw. With rain forecasted over the next several days, little infiltration will occur with a substantial or intense rainfall event and added nutrients will move with the water, often offsite. Although the ability to traffic a field may be the primary consideration for a producer, they should also think about what happens if a significant rainfall event occurs (offsite movement of nutrients). In addition to the environmental consequences, the loss of nutrients is an economic loss. Although it is tempting to “get over the ground” while it is frozen, be aware of the potential agronomic, economic, and environmental consequences associated with this decision. Be patient and wait to apply nutrients when soil and environmental conditions are more favorable.∆
DR. EDWIN RITCHEY: Extension Soils Specialist, University of Kentucky