The Results of the 2020 Home Orchard Fixed Daily Watering Experiment

This last orchard growing season, I watered using daily fixed schedules that took into account average daily evapotranspiration and estimated daily plant water use. I set up schedules for each month in the summer, since evapotranspiration and water usage changes significantly month to month. Previous years I had used a dynamic schedule determined by Rachio’s Flex Daily algorithm and Advanced Zone settings. The Flex algorithm greatly favors deep waterings and the interval is guided by daily estimated evapotranspiration. The trees often suffered on extreme California summer days under the Flex Daily algorithm — it watered too deeply and too infrequently so trees couldn’t get daily access to water with very high summer evapotranspiration rates. Flex does not account for extremely hot days where available water depletes, leaving trees struggling without water until the next day or longer. Fortunately, the Rachio irrigation controller makes it dead easy to create any number of watering schedules. The results of using fixed schedules tuned for each summer month this last growing season were pretty good. While the mandarins are undersized after the previous year’s bumper crop of well sized fruit, our Valencias and Meyer Lemons did great. The pineapple guavas also responded very well to daily watering with a surprising amount of growth. The avocados, while very finicky, did fine too. But it turns out no matter how much water they get, when temperatures go over 100 F their leaves scorch (so we had to rig up shade cloth over the young trees using ladders). Besides the avocados, the trees didn’t suffer greatly from heat stress with daily watering. I do wonder if the fixed daily waterings didn’t penetrate the soil deep enough, resulting in undersized mandarins, so next year I will try watering every other day and doubling the watering times. This should encourage deeper root development and perhaps provide more water to trees from throughout the soil column.

Scorched young avocado leaves despite daily watering:

Scortched, dried out avocado leaves despite daily watering.

Ryan Mikulovsky @kurite