The irrigation season in Canterbury has begun with a dramatic shift. After a wet early spring, soil moisture levels have dropped rapidly since early October, demonstrating a sharp contrast to last year, when the decline didn’t occur until late November or December.
This season, the fall in soil moisture has been far more pronounced. Many of our clients are now seeing moisture levels well below the lowest points recorded last year.
In several cases, irrigation appears to have had minimal impact on replenishing soil moisture. Interestingly, rainfall of the same volume produces a much greater effect. This is clearly illustrated in the following graph — while recent irrigation has barely lifted soil moisture, the 28mm of rain received on October 27–28 resulted in a significant increase.
Image 1 - Rainfall (Red) vs. Irrigation (Blue): Soil Moisture Response
It’s a timely reminder that rain is free and often more effective than irrigation in restoring soil moisture. In this instance, the irrigator was turned on again three days after the rain, and moisture levels quickly dropped back down. Subsequent irrigations have done little to recover the loss.
Continuing to irrigate either during rainfall or immediately after would have helped maintain that lift from the rain. Driving from Christchurch to the Ashburton Show in October, not one irrigator was running in the days following the rain - a clear sign that many missed an opportunity to hold onto those gains.
With more variable weather patterns becoming the norm, timing irrigation to complement rainfall rather than follow it is key. ADR’s soil moisture and network monitoring solutions give irrigators the insights needed to make those decisions confidently, helping protect both water resources and productivity throughout the season.
Learn more at https://www.watermetrics.co.nz/