Nitrate Losses from a Corn-Alfalfa Rotation: Lysimeter Measurement of Nitrate Leaching
1998
Toth, J. D. (John D.) | Fox, Richard H.
An array of 18 zero-tension pan lysimeters installed 1.2 m below the soil surface in 1988 was used to examine NO₃ leaching in 1991 to 1995. The experiment was designed to study NO₃ losses from continuous, fertilized corn, alfalfa, and the first year of corn rotated from alfalfa as a function of crop type, applied N fertilizer rate and longer-term weather variability. The flow-weighted mean leachate NO₃-N concentration from the 3-yr alfalfa stand was 4 mg L⁻¹. Annual leachate NO₃-N concentrations from continuous, fertilized corn and corn following alfalfa at the estimated Economically Optimum N (EON) rate averaged 15 mg L⁻¹. Annual flow-weighted average NO₃-N concentrations in leachate from post-alfalfa corn receiving 50 and 100 kg N ha⁻¹, which were above the EON rate, were 18 and 24 mg L⁻¹, respectively. The masses of NO₃-N leached from the root zone of continuous corn at the estimated EON rate were 81 and 55 kg ha⁻¹ in 1991 to 1992 and 1994 to 1995, respectively. Nitrate-N losses from alfalfa in 1991 to 1992 were 9 kg ha⁻¹. Nitrate concentrations in leachate from an alfalfa stand were one-quarter to one-fifth as high as from corn receiving the EON rate. This research provides evidence that including alfalfa in a rotation would result in a considerable reduction in the amount of NO₃ leaving a farm in leachate.
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