Irrigation systems for growing vegetables
Sprinklers should be chosen for the prevailing conditions that the irrigation system will be operating in. In the warmer months in Western Australia (namely October through to March), these conditions are often windy, with average wind speeds above 9km/hr. Butterfly sprinkler systems spaced at 6 x 6 m give high uniformity under windy conditions however the cost of installing these systems is high.
Drip irrigation systems work well for some vegetable crops and provide the opportunity for efficient irrigation and nutrient management.
Hydroponic production of vegetables can also be a highly efficient production system and is gaining popularity for tomato, capsicum and cucumber cultivation
For extensive areas of vegetable crops centre-pivot irrigation is a cost effective method of irrigation, although in summer on the Swan Coastal Plain, the area planted under large centre-pivots has to be managed because the high water requirements regulary exceed the application capacity of the pivot.
Impact sprinkler systems are the most common system used for vegetable production on the Swan Coastal Plain. For impact sprinklers systems, laterals and sprinklers should ideally be spaced at 30% of the throw diameter of the sprinklers being used, and should not exceed 50% of their throw diameter (i.e. a sprinkler that throws 24m should be 4
In the majority of vegetable growing properties using impact sprinklers, laterals spacings will be 12m or greater. Jet sizes 4.5mm or above (size 12) are usually required to produce the required application rate and throw diameter to achieve acceptable distribution uniformity at lateral spacings from 12-15 m and sprinkler spacings from 9-15 m. Below is a summary sprinklers testing that was done with recommendations made for windy conditions to achieve distribution uniformity above 80%.
A list of sprinkler type, nozzle and operating detail combinations that achieved distribution uniformities above 80% when measured in windy conditions (Lantzke et al. HAL final report) can be found at the following link, Impact sprinkler suitable for windy conditions.