It’s been a long dry summer with some areas in Canterbury, particularly mid, central and north, receiving very little rainfall since mid-December. Irrigation is a relatively simple task in dry weather, you turn it on, check the flow rate and system pressure are correct on a daily basis (this can be automated) and keep going until the weather forecast provides you certainty significant rainfall is coming. Through December and January, Lincoln and Winchmore climate station data shows ET rates averaged between 4.1 and 4.3 mm/day, and there were a couple of weeks where ET averaged just under 5 mm/day (the highest daily ET being 6.1 mm). You should have been irrigating flat-out during this period to meet plant water demand!
However, as we’re now heading into the autumn shoulder season, where days are getting shorter and daily temperatures are dropping, ET rates are starting to decrease. February ET rates at Lincoln and Winchmore are currently averaging between 3.2 and 3.5 mm/day and these will drop to between 2.5 and 3 mm/day during March. This means you need to start thinking about how frequently you irrigate alongside continuing to monitor weather forecasts for rainfall. Using a pivot irrigator as an example, instead of irrigating 15 mm every 3 – 4 days as you would have been doing during peak season, you should now be stretching this out to 15 mm every 4 – 5 days and then every 5 – 6 days.
Alongside closely monitoring climate data and weather forecasts, another aspect we’ve observed this season that we’ll be helping our clients with next year, is the need to better time irrigation applications with grazing rotations. We’re aware of some science that has been undertaken this season that shows grazing (particularly cattle) during or within a day of irrigation can have a big impact upon your soil quality. Grazing wet soil effectively squashes it, reducing the number of micropores within it (micropores are where the soil water is held), which then reduces the soils water holding capacity and impacts upon other soil processes. Whilst better timing irrigation applications with grazing rotations will certainly make irrigation a more challenging task, noting the ability to remote control irrigation equipment will help make this more achievable, it’s a key consideration if we are to more effectively use the water we are applying, from both a production and environmental perspective.
If you would like specific support or advice for your irrigation scheduling, an assessment of your scheduling practice (including practical suggestions around how your irrigation practice could be improved), or you have issues with your irrigation equipment call Water Strategies to book in your Irrigation WOF.