Rethinking chill hours for California Pistachios and Almonds orchards to counter climate change. 

We know that fewer chill hours mean less yield or worse a mix of flowering times between the cross pollinators, which causes a complete loss of the crop.

Research in this area has always measured chill hours at the surface. But why? The trees are dormant as they come back from their deep sleep, it is the roots that start to wake up first, to feed the hungry hibernating tree. What wakes up the tree? Is it the warm ambient surface temperature or is it the warming of the soil? 

Being a native Californian, warm days in the middle of winter are common. I would say it is the warming of the soil that wakes up the trees causing an off balance of equilibrium.

The Problem

The problem is that the orchards with fruit and nut trees need their dormancy, so that for a period of time the orchard trees sleep. Therefore without sleep, yields are lower or blooms are out of sync with cross pollinators. 

In California, we have the great benefits of warm beautiful winter days, low atmospheric water vapor, and warm winter soil to grow crops year-round. But these are all counterproductive for California orchard trees. Why? because the current irrigation practices of drip and micro sprayers encourage shallow roots near the surface. In theory, the warm winter soil wakes up the tree’s roots from their dormancy because they are so close to the surface.

The Solution of Increase Chill Hours

We believe the solution is deeper roots away from the winter heat. So the plants remain dormant. The hypothesis is that deep roots will shield the tree from the warm winter soil and increase the chill hours based on the soil temperature in the root zone and not up at the tree buds. Presently the difference with current growing practices, measured chill hours are from the surface up to the fruiting buds and not at the roots. 

We know that the tree roots go through a dormancy, that is why new bare root trees can be shipped and planted in wintertime. So the question is? Can we keep tree roots in a dormant state at the depths of 3 to 5 feet?

Other Benefits

There are other benefits of deep-rooted trees:

  • Trees with deep roots have less chance of blow over.
  • Deep tree roots are protected from herbicide sprays.
  • Deep-rooted trees protect the orchard from extreme summer heat days.
  • Deep roots have greater access to soil moisture volumes.
  • Deep tree rooted trees suffer less during nut harvest.

Virtual Water Table

How do we get tree roots to grow deep? One of the solutions is by creating a virtual water table five feet below the surface so that the trees feed on the moisture plume created above the virtual water table. This moisture plume is created underneath the middle of the service road. In other words, it is three feet below the surface and is 14 feet wide. Hence the moisture plume is always available, the trees push their roots deep into the area, and away from the surface.

The Aquifer Pipe

Our solution to this problem is our product, the Aquifer Pipe. It’s a six-inch pipe and comes in 20-foot lengths that can join with couplers, increasing the total length to a full mile.

Some people like to call it a smart drain tile, because of its unique pipe shape. It is designed in a V shape to store water. The water allows the soil inside the channel to saturate it (a virtual water table). A moisture plume is then created that is two feet high and 14 feet wide.

Let UmidaAG help you protect your orchard by assisting the trees to remain dormant in the winter. It’s a rude reality that our California winters are only going to get warmer.

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