Nitrate Leaching from Nitrogen‐Fertilized and Manured Corn Measured with Zero‐Tension Pan Lysimeters

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Abstract
Excessive N fertilization increases the potential for nitrate (NO−3) leaching, but no research has evaluated NO−3 leaching from corn (Zea mays L.) receiving economic optimum N rates (EON). This study assessed (i) flow‐weighted average concentration and mass of nitrate‐N (NO3‐N) leached from nonmanured and manured corn treated with five fertilizer N levels and at EON, and (ii) the relationship between NO3‐N mass in the 1.2‐m soil profile following harvest and the flow‐weighted average leachate concentrations. Following application of liquid dairy manure each April, the field was chiseled and disked prior to planting. Ammonium nitrate was broadcast at planting (0–200 kg N ha−1 in 50‐kg increments and 0–100 kg N ha−1 in 25‐kg increments) in the nonmanured and manured corn. Eighteen (0.465 m2) pan lysimeters were placed 1.2 m below the soil surface in zero, intermediate, and high N treatments. Zero‐N plots had 3‐yr average flow‐weighted leachate concentrations less than 10 mg NO3‐N L−1. At EON, the 3‐yr averages were 18.8 and 19.3 mg NO3‐N L−1 for nonmanured and manured corn. Nitrogen rate influenced mass of NO3‐N leached only when collection efficiency estimates were used to account for pan bypass flow. In the nonmanured corn, the 3‐yr average amount of NO3‐N leached was 107 kg ha−1 or 36% of the N applied at EON. Total mass of NO3‐N in the 1.2‐m soil profile following harvest was useful to predict annual flow‐weighted average leachate NO3‐N concentrations, but this is not practical in most soils of the Northeast.

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