1 March 2017, 02:49PM
As we come off one the back of a sizzling summer and into an autumn forecast to be warmer and drier than average, it is not surprising farmers are looking ahead and planning for how to better manage their water usage for the growing season ahead.

The challenges facing producers today means more and more people are looking for drought solutions even in areas where irrigation is not traditionally used. In many areas, surface irrigation (“flood”) is still a common technology. There are some advantages to this method; initial investment is relatively low, and you can, to some degree, substitute unskilled labour for equipment. Besides, what could be simpler than running a stream of water downhill in a furrow?

However, there are disadvantages, as well. Efficiency and effectiveness are two desired elements of a good irrigation system. By “effective,” we mean no less water than necessary. By “efficient,” we mean applying no more water than necessary. When you add the variable of “uniformity” (treating every area of the field effectively and efficiently), surface irrigation leaves a lot to be desired. Furrow-irrigated fields tend to be overwatered at the upper end of the field and under-irrigated farther down the length of the furrow.
Over-watering leads to deep percolation (water draining below the root zone) or running off the field, lost to the crop. This affects not only its efficiency (surface systems are typically 40 – 60% efficient), but also tends to leach nutrients out of the root zone. This adds to fertilizer costs, increases the risk of groundwater contamination and leads to reduced production due to water-logged soils.

Although the initial investment is higher for a centre pivot, there are several advantages that make it a worthwhile drought solution. Let’s start with effectiveness and efficiency. First, remember that management is critical to success with any system. A poorly managed system can be ineffective and inefficient regardless of technology. 

Centre pivots are (or should be) very effective. The system is designed with the capacity to maintain maximum yield. Designers use their knowledge of crop evapotranspiration (ET), or crop water use, to provide a system that allows timely irrigation to meet crop needs. A pivot should also be efficient. With regular applications of small depths of water, there should be no surface runoff, nor should there be any deep percolation. Typically, we expect a well-designed, well-managed centre pivot to achieve water application efficiencies in the 85 – 95% range. Pivots can also provide effective, efficient irrigation to sloping areas not suited to the surface method.

When we add the uniformity component, pivots again shine. A good sprinkler package will maintain high application uniformity over the entire field. Sprinklers also allow the operator to leave room in the root zone for rainfall events. This prevents losses due to deep percolation when a significant rainfall event occurs during the growing season.
Another potential advantage of centre pivots is the opportunity for fertigation. Fertigation involves adding fertiliser to the water stream, which allows the application of fertiliser at any time the pivot runs. This improves efficiency by allowing a producer to “spoon-feed” nutrients to the crop exactly when they are needed. It also lowers application costs and guarantees uniformity will be the same as the uniformity of water application.

As you plan and prepare for the season ahead, we hope this provides a little information to help you make informed decisions.

For more specific information on what a centre pivot can do for your yields, speak to the experts at TEAM Irrigation, one of the largest regional irrigation companies in Australia, on 02 6885 5220.

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