Where is that perfect irrigator?
Many years ago, Alan Brown from MAF Ashburton commented to me that no one had invented the perfect irrigation system. Decades later, there is still no perfect irrigation system, but we have made considerable progress. Improvements have been and will continue to be made with physical components and with electronics.
In my view, the three methods that particularly stand out in terms of the ability to provide the most efficient application of water for field irrigation using current technology are centre-pivots, fixed grid and subsurface drip. They allow precise control of water application and have the added bonus of requiring very little labour to operate.
Centre-pivots, which now cover more irrigated land than any other system in NZ, have enabled water to be applied as and when needed in an efficient manner. While there are still some challenges such as high application intensities under some pivots, generally the pivot irrigation industry has adopted good design practices to enable efficient application of water. With pivots, variable rate irrigation or its equivalent is widely used enabling application depths to be controlled at any location in a field. Low energy precision application systems such as drag hoses with associated flow control adaptors are being introduced into NZ, and high-tech nozzles with multiple functions are now being used.
Fixed grid or solid-set sprinkler systems have advanced considerably, especially with their ability to apply water when and where needed. While the electronic control of these systems has improved markedly over the last few years, there are still some design challenges to resolve around how best to use this method on hill slopes. However, work is being done to address these issues and they should be resolved.
Subsurface drip irrigation (SDI) is a very advanced method of irrigation. Other than cost, the biggest challenge with buried drip tube is preventing emitter blockages and stopping crop roots intruding into the emitters. Once again, recent developments have helped. Now, it is relatively easy to set up systems for automatic filtration and flushing to keep emitters clean. While previously, acids and pre-emergent chemicals were used to control root intrusion, today metals such as copper are being impregnated into the drip tube to provide the protection.
Where the irrigation industry is changing most rapidly is in the integration of irrigation equipment with sensors to optimise operation and control. Irrigation control systems now allow for full remote control of pivots and other equipment, such as pumps, fertilizer injectors, pressure sensors, flowmeters, soil moisture sensors and climate stations. These systems can be operated via the internet on a mobile phone, PC or laptop. The next generation of digitisation has the potential to make irrigation a completely automated process.
As electronic systems and associate software have become more reliable, real-time measurements can be used to determine crop water needs and fully controllable irrigation infrastructure can apply water where and when needed based on those measurements. Even without the automation, real-time soil moisture and crop water use monitoring is already providing considerable value to farmers and growers for making irrigation decisions.
Solar power is starting to have an impact on energy use in the irrigation industry. Solar water pumps have been used for many years. As PV systems are easily scalable, there is no reason why they can’t play a much greater role in irrigation.
And about the perfect irrigator, maybe we should be thinking of replacing long-line sprinklers with solar powered robot irrigators. After all, people are already using robots to mow their lawns! Believe it or not, prototype robot irrigators already exist.
