ISHS Acta Horticulturae 792: V International Symposium on Irrigation of Horticultural Crops
IMPROVING TRICKLE IRRIGATION: BETTER MATCHING TRICKLE SYSTEMS DESIGN TO SOILS |
| Authors: | P.J. Thorburn, F.J. Cook, K.L. Bristow, P. Fitch |
| Keywords: | soil structure, infiltration, WetUp, unsaturated flow, irrigation scheduling |
| Abstract:
It is recognized that trickle irrigation systems can deliver water (and chemicals) to the root zone of plants more efficiently than most other forms of irrigation. For trickle systems to operate efficiently, the two variables most easily manipulated when designing systems, the distance between emitters and emitter flow rates, must be matched to both the soil's wetting characteristics and the amount and timing of water to be supplied to the crop. This principle is rarely adopted during system design, possibly because most practitioners do not realize the variability in wetting patterns amongst different soils. To illustrate this variability, an analysis of wetting patterns was undertaken based on hydraulic properties of a wide range of soils from the Bundaberg area in Queensland, a region area with large areas of trickle-irrigated small crops. There was a wide range of wetting patterns in these soils, but there was no relationship between the wetting pattern and texture, indicating that soil texture is an unreliable predictor of wetting. The results have practical implications, suggesting that emitter spacings and flow rates commonly used in small crops in this region are unlikely to be well matched to the wetting patterns. This is likely to be the case in other crops as well. To demonstrate the variability in soil wetting for trickle system designers and irrigators, a simple software tool "WetUp" was developed based on the models and databases used in the analysis. Once it is seen that the soil structure allows a sand to “behave” like clay and vice versa, more effort should be put into obtaining site-specific information on soil wetting prior to design and installation of trickle irrigation systems. Then, trickle irrigation may deliver the irrigation efficiencies expected from the system. | |
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