Nitrate Leaching from Nitrogen-Fertilized and Manured Corn Measured with Zero-Tension Pan Lysimeters
1994
Jemison, John M. | Fox, Richard H.
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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