Measuring Deep Soil Moisture Matters, Even During a Wet Year

Monitoring soil tension at 36 inches is critical to almonds year round.

IMG_6815This past winter has been a wet one for the San Joaquin Valley.

The season brought record amounts of rain to some regions, giving growers hope for a strong season despite four consecutive years of drought and numerous water issues.

But even with all of the rain this winter, recent soil samplings and Hortau tension graphs show some almond growers in the Central Valley are surprisingly behind when it comes to their irrigation management programs early in the season.

During the recent bloom, Hortau sent its team of grower support specialists into a handful of almond orchards in the area to see where growers’ almond orchards were at in terms of soil moisture.

Hortau, which uses soil tension sensors to measure plant stress and available water to a tree in real time, discovered that while the region has received a considerable amount of rainfall, some almond orchards surveyed have not received the deep soil moisture needed to maximize production this year.

Using Hortau’s soil tension platform, growers can identify the ideal “comfort zone” for an almond tree at various depths. High soil tension (over 35 cbars), means an extremely dry soil profile and high amount of stress for the trees going into the spring.

As of mid-February, some growers were satisfied their blocks have received enough moisture at the 36-inch depth, but as the following soil tension graph suggests, that is not the always the case, even in a wet year:

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The above graph from Hortau’s proprietary soil tension management platform shows all three soil tension sensors (18, 24 and 36 inch depths) on Block A were severely stressed by mid-February and that trend continued through Feb. 18 when the following field soil samples were taken, backing up the dry soil profile data at 36 inches:

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Hortau’s soil tension management platform allows growers to monitor tree stress in real time year-round.

These examples from Block A show almond trees going into full bloom, a critical time for a growing almond tree.

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By comparison, Block A (pictured above) saw about half the bloom and budset of similar-aged trees on a healthier-looking Block B, (pictured below).

Block B shows all three soil tension sensors were well within the ideal soil tension range (or blue band) for almonds through the same six-day period in mid-February (Feb. 13-Feb. 18):

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The above graph from Block B showed a much more full bloom and budset (photos below), thanks to proper irrigation management that included keeping soil tension well within the ideal comfort zone (10 to 35 cbars). Keeping trees in the identified soil tension zone also prevents overwatering, which can lead to leaching and also have a negative impact on bloom and root development.

Coming out of bloom, it’s evident from the graphs, soil samples and the overall health of the trees, that Block B is better positioned to have a successful season in 2016.

Here are some photos from the almond bloom at Block B, in similar age trees and variety as Block A:

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While there are a number of factors that contribute to having a successful growing season, ensuring almond trees are within their optimal soil tension range at all three depths throughout the year has proven to greatly increase production, overall tree health and also prevent over-watering and leaching of critical nutrients and fertilizers.

To learn more about Hortau’s proprietary irrigation management systems, and our work in almonds and other crops throughout the U.S., visit Hortau.com or call (805) 545-5994.

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