Nitrogen watch for well- and moderately well-drained soils

Well-drained soils are vulnerable mainly to nitrogen loss from leaching. This process can start shortly after fertilizer application (with some delay for ammonia). We have used April 1 to represent a preplant N application date. For ammonia or for applications later than April 1, risk is lower; for applications before April 1, risk is higher. 

Areas with diagonal shading are ‘danger areas’ that are on track to have 16 or more inches of rainfall from April 1 to June 30.  This does not mean that significant loss of N has already happened, just that producers in these areas should be watchful and aware of the potential for N loss and deficiency.

Areas shown in cross-hatch are ‘problem areas’ that have already received 16 or more inches of rainfall since April 1.  I expect a majority of fields to have substantial yield loss due to N deficiency when all N was applied pre-plant.  I suggest that producers look at their fields and when N stress is seen apply additional N.  Rescue N applications are likely to be profitable until tasseling or later in fields with deficiency symptoms.  Canopy sensors potentially provide a way to improve distribution of this N application, putting more N where stress is greatest and little or none where corn looks good.