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Journal of Environmental Quality Abstract -

Soil Nitrates Following Four Years Continuous Corn and as Surveyed in Irrigated Farm Fields of Central and Eastern Colorado1


This article in JEQ

  1. Vol. 5 No. 1, p. 82-86
    Received: Apr 21, 1975

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  1. A. E. Ludwick,
  2. J. O. Reuss and
  3. E. J. Langin2



High rates of fertilizer N used in many intensive farm management systems have been cited as a potential pollution hazard to surface and ground waters. The purpose of this study was to evaluate soil NO3 accumulations following 4 years continuous corn (Zea mays L.) grown with different nitrogen and irrigation regimes, and to compare these results to present NO3 concentrations found in irrigated farm fields of central and eastern Colorado.

Soil NO3 content in the 300-cm sampled profile was significantly influenced by both fertilizer N and irrigation treatments; the greater accumulations were associated with the two higher fertilizer N rates and two lower irrigation rates. Nitrate increased linearly in relation to fertilizer N between 67 and 269 kg N/ha and could be described by two simple regression equations separating the irrigation treatments into two groups (l-2 and l-3, low rates; l-4 and l-5, high rates). Coefficients of determination for the two groups were 0.981 and 0.975, respectively.

Two hundred and seventy irrigated farm fields were sampled to a depth of 90 cm in central and eastern Colorado. Mean soil NO3-N content was 173 kg/ha and contents were not significantly different between coarse and fine textured groupings. Fields sampled immediately following beans (Phaseolus vulgaris L.) contained similar amounts as those following corn. Mean soil NO3 content decreased with greater soil depth.

Observed NO3 concentrations appear to be the result of gradual accumulations from annual or near-annual fertilizer N and/or manure applied over a period of time. Data from the 4-year corn experiment clearly illustrate that NO3 can accumulate in a soil profile even when fertilizer N is applied at rates below that required for maximum production.

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