As early season irrigation commences, one of the questions our grower support representatives are often asked is should they irrigate when soil tension rises at one depth, while other levels remain in the comfort zone?
An attendee at one of Hortau’s recent presentations pointed out on one of our graphs from a Central Valley almond orchard that soil tension was rising in one particular section of the soil profile, while the other two sensors indicated that soil tension was optimal at the other two depths, presenting the question of whether or not to irrigate.
Question: “After the 5/21 irrigation, you see the blue line go up and it’s beyond the comfort zone, but the other two are still down. Would you irrigate?”
Hortau Director of Grower Support Ben Smith had this response:
I would irrigate.
What’s going on here is the blue line is a soil tension sensor at 18 inches. Green is 24 inches. Red is 36 inches.
What we’ve seen across quite a few crops is early on in the season they’re not very good at pulling water from deep. It’s just like a well: the deeper the water is in the ground the more force is required to pull it up.
Early in the season when it’s not very hot, it’s harder for the plant to really access that water that’s down deep. It takes more energy. They tend to feed a lot off that shallower water. So in this case what would you do? You’d irrigate, but you do a short irrigation set only to bring that line down.
You don’t have to irrigate the entire profile every time, just irrigate the ones that need it. So what you do in this case is irrigate frequent, short irrigations to control the top line and once the other ones get high enough a longer irrigation will move them all down.
Generally, as you get a little further in the season like June and July, it’s hot enough that the trees are pulling from all the depths and you really have to irrigate more to move it through.
- Crops pull water from shallower depths early on in the season
- Short, frequent irrigations will keep soil tension in the comfort zone at the top of the profile where plants are pulling
- Come summer and warmer weather, plants will pull from all depths and more irrigation will be needed to move water through the profile