A panel of Indiana Certified Crop Advisers addressed concerns about nitrogen loss in corn following heavy rains, according to a May 27 discussion. The panel included Betsy Bower, Purdue Extension senior research associate; Abby Horlacher, Nickel Plate Consulting; Brian Mitchem, Farmer 1st Agronomy Consulting Services; and Dan Quinn, Purdue Extension corn specialist.
Bower said that applying a rescue nitrogen application should be carefully planned. “Consider nitrogen source, soil type, rainfall timing, nitrogen application methods, nitrogen stabilizer use, and current health of the crop.” She explained three main mechanisms of nitrogen loss: volatilization of ammonia when urea-based fertilizers are surface-applied; leaching of nitrate on sandier soils; and denitrification on poorly drained soils. Bower recommended taking soil samples at 12 inches deep to determine if there is a deficiency: “By knowing the nitrogen concentration in the upper foot and stage of crop, you can then understand if you have any nitrogen deficiency.”
Horlacher said that deciding on rates and timing for supplemental applications is challenging with this year’s weather. She recommended using the pre-sidedress nitrate test for more accurate field assessments: “For accurate results, sample at least three representative areas within the field to gain a better understanding of overall field conditions.” Horlacher also advised considering available equipment or aerial application if ground access is limited.
Mitchem said saturated soils can lose significant amounts of nitrate each day depending on temperature and duration: “Warm and saturated soils can lose 4% to 5% of the nitrate each day the soil is waterlogged.” He suggested estimating lost nitrogen first and looking for yellowing symptoms before deciding on additional applications. Tissue sampling from multiple areas was also recommended as a diagnostic tool.
Quinn explained that losses may occur through denitrification or leaching depending on soil type and fertilizer source. He said visual symptoms such as yellowing lower leaves indicate possible need for supplemental applications: “If significant nitrogen loss is suspected, rescue applications made before pollination or just after can help preserve yield potential.” Quinn recommended liquid forms applied with high-clearance equipment targeting affected areas only.
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