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This article in SSSAJ

  1. Vol. 41 No. 3, p. 496-499
    Received: Jan 9, 1976
    Accepted: Sept 27, 1976

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Miscible Displacement of Nitrate and Chloride under Field Conditions1

  1. C. Misra and
  2. B. K. Mishra2



In an attempt to develop the capability for predicting the reduction loss of NO3-N during leaching of nitrate fertilizers in an Oxisol field profile, a 2-cm pulse of Ca(NO3)2 solution containing 304 ppm of NO3-N was displaced through a 300-cm by 300-cm field plot saturated with water down to the depth of 55 cm. On the following day an identical pulse of NH4Cl solution containing 795 ppm of Cl was leached through the same plot. The results were analyzed by means of a convective diffusion type transport equation that incorporated an irreversible first-order sink term. The agreement between the observed and the theoretical breakthrough curves allowed the determination of the first-order reduction rate constant for NO3-N as 0.1 hour−1 at an average soil temperature of 34°C. Under these conditions, the recovery of added NO3-N in the leachate was 70% whereas that of Cl was 100%, approximately, when the two pulses moved past the 55-cm soil depth. The apparent diffusion coefficients for NO3-N and Cl were velocity dependent and ranged between 41 cm2 hour−1 to 80 cm2 hour−1, corresponding to the pore velocity range of 11.5 cm hour−1 to 17 cm hour−1. Although the present model was reasonably successful in predicting transport of ions undergoing microbial transformation in a natural soil, a more appropriate treatment should consider ion movement in stagnant and mobile phases in the soil pores in view of greater precision in working out the kinetics of biodegradable solutes.

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