An irrigation system supplies water to farms through artificial supply channels or canals. A rice farm also has supply channels which provide water to crops and pastures. Crops may be grown in several types of irrigation layouts which may all be used on the one farm. The three main layouts used on a rice farm are:
1. Natural contour or landformed contour irrigation systems
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Contour systems are the main irrigation layouts used in the rice growing areas of eastern Australia. Banks are built along the natural contours. In natural condition the soil surface between the banks may be uneven which causes uneven water depth and the irregular shape of the bays causes inefficiency with machinery operations. Hence most rice farms have upgraded layouts using laser levelling to create a uniform grade and soil surface with parallel contour banks and regular sized bays. The machine that makes the level irrigation system is called a laser level and the process is called land forming.
The contour irrigation system used for rice production enables rice bays to be flooded and the water held at specific depths. The water depths are different depending on the stage of the rice crop. The rice farmer needs to be able to quickly raise and lower the water depth. As the rice grows, the farmer must make sure that the depth of water is sufficient to inhibit weed growth; to protect against cold temperature damage; and to maintain enough water to replace evaporation during the hot summer months.
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This layout is the most popular with rice farms in Australia, especially those with crop rotations of rice, wheat and pastures.
2. Border check systems
The border check system is mainly used on steeper land not naturally suited for rice farming. With this system, banks are built down the slope to ensure adequate drainage for a range of crops and pastures. If rice is grown, the banks need to be removed and erected at intervals across the slope as for the contour layouts. Because of the changeover in banks border check systems usually have longer rice rotations. It is usually two to three years of rice followed by a 4- 8 year crop and pasture phase.
3. Furrow systems
Furrow systems are raised irrigation beds that are built down the slope or on flat slopes with banks on terraces. Raised beds may vary from 1-2 metres wide. They are widely used for summer crops of maize and soybeans and winter crops in the Murrumbidgee valley. Research has demonstrated rice can be grown in bed layouts but so far only a few growers are growing rice in bed layouts since yields and water use efficiency are no better than for the other layouts. The advantage of rice in beds is for the following double winter crop because of the good drainage gained from the furrows.