@Dan in CA wrote:
For controlling irrigation with soil moisture probes, multiple probes at different depths are generally used at each monitoring location. The frequency of irrigation is controlled by shallow probes and the duration of each irrigation is determined by deeper probes.
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Shallow soil moisture is easy to accurately predict from an ET models. Variance over time from ideal will show up in the soil deeper in the rootzone. Also by just walking the lawn most people can tell if the top couple inches has dried out. So I believe that accurately measuring deeper moisture is more important than determining overall average moisture, especially when growing non-annuals (either ornamental or agricultural)
Testing soil probes for accuracy at determining when field capacity is achieved seems like an important early effort. Accurately flagging field capacity allows a reset of the ET model at 100%, zeroing out any drift in the model from reality. This may not be relevant to users with little rainfall, as I assume soils at field capacity are an infrequent occurrence.
Acclaim soil sensor install :https://www.youtube.com/watch?v=W4Wninln-uk
As a long term goal, perhaps accumulating user adjustments is worthwhile. Does a particular user choose more or less water than the model suggests? Do all user have a tendency towards altering irrigation towards more or less water?