84 | Stephen McNally, Principal Technical Advisor, INZ. IRRIGATION » Irrigation New Zealand • from page 83 the latest in irrigation technology, says Vanessa. “The three components of that are that the irrigation system can apply water really efficiently, that the water is used in a justified manner and that there’s a monitoring system in place providing evidence of efficient and justified use. It’s about testing your soil and understanding what your roots need, what the weather patterns are and how they will impact a crop the days before and after. It’s about being a lot more in tune with the data and information around you.” While there are good examples of SMART irrigation being used in the horticulture and viticulture sectors, Vanessa says there is also inconsistency and a lack of sharing knowledge in respect to good irrigation practices.“That’s partly because SMART irrigation is relatively new and, in terms of farm environmental plans and approaches, there hasn’t been the focus on viticulture and horticulture that there has been in other primary industries. When there’s a focus on an industry and the application of water and nitrogen, you get better outcomes. So there’s definitely room for improvement, and we have some amazing designers coming through now.” SMART irrigation reduces wastage and reduced wastage means reduced cost, straight off the bottom line.“Roots under trees and vines are not being watered unnecessarily, and they absorb the right amount of water at the right time, so it’s also better for the health of the plant. We’re definitely seeing movement towards smarter technologies and understanding. We’re seeing more horticultural specialists, and we’ve done quite a bit this year with Zespri and HortNZ, in particular around improving irrigation management of orchards.” Ninety percent of New Zealand’s fruit and veges require irrigation. Vanessa suggests we could do such a better job if all ninety percent had SMART systems in place, really understood what their plants needed at that point in time and stored the water as they needed it — rather than relying on rainfall. “You can imagine how much improvement there would be in the sector.” The ability to capture/hold rainfall within the soil pro ile is key to enhancing irrigation e iciency and reducing environmental impact. This usually means running a soil moisture de icit (during irrigation) to hold rainfall. It also means withholding (stopping) irrigation in the days immediately prior to signi icant forecast rain to optimise that capture. The challenge has been, and always will be balancing the risks. New Zealand’s weather patterns provide a huge challenge for irrigation scheduling. Running a signi icant moisture de icit (say 10mm) on light soils (say Plant Available Water = 40mm) is a scary proposition for many. Stopping irrigation for a day or two when Evapotranspiration is running 5 6mm/day in the face of predicted rain requires a leap of faith. A relatively new tool to help with these important decisions around irrigation scheduling is predictive soil moisture. If you are familiar with soil moisture probes and tapes and the role they play in irrigation decision-making, then predictive soil moisture is simply the “forward-looking” version of that. The technology typically combines forecasting data from a local source (eg: a forecasting weather station) with local probe data to create moisture predictions, (eg: 4 days in advance). Scenarios can be created to compare “with” and “without” irrigation (see graph). The idea is it allows users to quickly assess the impact of stopping irrigation on their soil moisture and therefore assess risk. Predictive Soil Moisture Probes the Way Forward The tool helps answer scheduling questions such as: • Rain is predicted, do I turn o irrigation now to save water and what is the risk? • Soil moisture is tracking well, can I shut o for a day or two to reduce a potential drainage event if rain arrives later? • If I turn o irrigation today, how many days storage do I have before I must irrigate? To help with decision-making, powerful algorithms create irrigation recommendations. Combined with automated alarms/alerts, the idea is the burden of risk is reduced and more informed decisions can be made. Contact your local WaterForce Branch on 0800 436 723 or visit waterforce.co.nz.
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