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Irrigation scheduling myths

Irrigation scheduling myths

During our recent irrigation scheduling workshops, we’ve come across some ‘interesting advice’ that’s being provided by a couple of telemetry service providers. Here’s a few of our favorites, along with the correct information.

The same amount of rain often gives a much higher response than the same amount of irrigation.

While soil moisture probes are clever, they aren’t clever enough to distinguish between rainfall and irrigation water. They only measure the amount of water in the soil. If your probe isn’t responding very well to irrigation look at the irrigator next time it goes over the probe, or better still put a bucket out and measure what’s coming out of the irrigator over the probe. It’s likely there are blocked nozzles or pressure issues, and your irrigator is putting on less than you think.

Air/soil temperature causes the field capacity to change.

The field capacity is the maximum amount of water held in the soil after the excess water has drained away under gravity, usually 12-24 hours post a heavy rainfall event. Temperature has no effect on the soil physical characteristics and therefore the field capacity will not change according to temperature. In this case the soil moisture probe in question was one of the cheaper capacitance probes that was likely faulty.

The data spikes are caused by spiders in the telemetry box.

Must have been a big spider… Soil moisture data spikes are normally caused by wiring issues or failing sensors. Incorrectly installed probes can also produce spikes when they measure air gaps around the probe instead of water.

Stay at the top of the ‘green zone’/optimum zone all season.

For anyone that’s attended our workshops you’ll know why this is a bad idea. You want to make use of the free water from the sky, especially during the shoulders of the season when it’s more likely to rain. If your soil profile is run at or near field capacity, any rainfall you receive will go straight through the soil profile and drain away, giving you no benefit at all, apart from giving more money to your electricity supplier for your extra pumping costs. It also increases your nutrient losses.

If you have soil moisture data that doesn’t make sense or don’t have any data, talk to the team at Primary Insight. We have an introductory special running on soil moisture probes until July 31 and we can also help you troubleshoot issues with your existing soil moisture data.


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