Nitrate Losses from a Corn-Alfalfa Rotation: Lysimeter Measurement of Nitrate Leaching
- John D. Toth * and
- Richard H. Fox
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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