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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 shown in cross-hatch are ‘danger areas’ that are on track to have 16 or more inches of rainfall from April 1 to June 30. Areas shown in purple or pink have already reached 16 inches and are expected to have widespread problems with N deficiency in well-drained soils. Areas shown in blue are on track to have widespread problems if precipitation continues at the same rate through the rest of June.
Aerial photos can help to assess the need for additional N on corn between waist-high and tasseling and are available from AgriVision.
