The Effect of Discharge Rate and Intermittent Water Application by Point-source Irrigation on the Soil Moisture Distribution Pattern1
- I. Levin2,
- P. C. van Rooyen3 and
- F. C. van Rooyen4
A comparison was made between the results of laboratory and field experiments regarding predictions of soil moisture distribution from a point source on the one hand, and those theoretically calculated by a computer simulation model (Bresler, 1975) on the other hand. A good agreement was found between computed and experimental data. When the verified model was used for predictions regarding soil water distribution under point-source irrigation, it was found that when the same total amount of water (12 liters) was added to the soil with a 2, 4, or 8 liters/hour continuously applied trickle source, a loss of 26% of the total amount applied was affected below the 60 cm depth after 12 hours. The initial water content of the soil was adjusted to the field capacity value. Under identical conditions I liter/hour continuously applied and 2 liters/hour pulsed (intermittent) irrigation resulted in only a 12% loss. The lateral distribution of the water showed that in the first group of treatments 80% of the water in the wetted soil volume was distributed 45 and 43 cm horizontally from the point source after 12 and 24 hours respectively. In the second group of treatments the distribution was to 29 and 40 cm. Thus the second group of treatments showed a clear advantage in reducing water loss under the root zone while still not significantly affecting the horizontal distribution. The pulse treatment can therefore replace the advantageous low (1 liter/hour) discharge rate while to a large extent avoiding the difficulties of blocking of outlets by maintaining a higher (2 liter/hour) discharge rate.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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