The Movement of Water and Nitrate Around Bands of Sodium Nitrate in Soils and Glass Beads1
- G. R. Burns and
- L. A. Dean2
The movement of water and nitrate (NO3-) around bands of NaNO3 was studied in soils and glass beads in the laboratory. A hypothesis was developed and tested concerning the predominantly downward movement of NO3- from a band of NaNO3 in soils with moisture contents greater than field capacity. The hypothesis of events is as follows: Soil water moves, under the osmotic force generated, to the band of NaNO3; then the NaNO3 dissolves and diffuses away from the band. However, the effect of the diffusion is reduced when sufficient mobile water is present in the surrounding soil to maintain the influx of water. As a result, the NaNO3 solution accumulates in the vicinity of the band. Once the accumulating solution exceeds that which can be held by the capillary forces of the soil, the excess NaNO3 solution literally drops out of the band under the force of gravity. The drop-out of NaNO3 solution continues until essentially all of the NaNO3 has been dissolved.
This drop-out phenomenon occurred in systems in which the water was present initially in quantities greater than field capacity, was moved through the system by leaching, or was moved into the system by capillarity from a shallow water table. Evidence supporting the details of the hypothesis resulted when various shields were used to alter the NO3- movement around the fertilizer bands under the leaching and “static” moisture conditions.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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