In California, we're quickly approaching the point in the growing season when almond growers and their irrigation managers are planning deficit irrigation strategies around hull split. Are you ready?

 

What is deficit irrigation?

Deficit irrigation is a strategy where irrigation is reduced to purposely induce stress on trees.

In years where less water is available, deficit irrigation in almonds can be used without too much of a negative effect on yield if it’s carefully monitored. For almonds, this strategy is most commonly used around hull split.

 

Why use deficit irrigation around hull split

Every year during late June or early July, a deep “V” begins to form in the hull, exposing the shell and almond inside. This split can be dangerous to the still-developing soft shell as it leaves it most susceptible to diseases like hull rot or navel orangeworm damage.

Hull-Split

Example of almond hull split, where the split exposes the soft shell inside

 

To limit the potential damage to the crop during this vulnerable period, growers can use a deficit irrigation strategy. When deficit irrigations are strategically planned around hull split, the nuts on the tree can dry out quicker. The regulated stress can also reduce the window where your orchard is vulnerable to damage.

 

How to plan for a deficit irrigation strategy

It is important to note that if done incorrectly, deficit irrigation can have a negative impact and actually delay hull split or result in a loss in kernel yield. Here are some tips and tools to help you form a deficit irrigation strategy.

 

General guidelines on the timing and duration of deficit irrigation

1. When a “V” begins to form on the hull just prior to the start of hull split, irrigations should begin to decrease. During this time, if your soil moisture levels are already depleted, it’s important not to induce any more stress than what is already there.


2. The period of deficit irrigation should last no longer than two weeks to prevent any long-term damage. Inducing too much stress for too long is detrimental to your crop as this final phase in development is occurring in preparation for harvest. When your two weeks of deficit irrigation are finished, resume your irrigation schedule and begin to fill the soil profile again just before harvest.


 

Make informed deficit irrigation decisions with Semios tools

1. Evapotranspiration (ET) monitoring: ETc can be reduced by 50-70% to regulate deficit irrigation. While many growers have relied on the nearest public or regional weather station for ET information, Semios’ in-canopy sensors provide the most accurate ET readings based on your unique in-canopy conditions and topography.

UI-Screenshot_Evapotranspiration

2. Soil moisture levels monitoring: During deficit irrigation, irrigation can be reduced until soil moisture levels deplete below 50%. Semios provides insights into the available water content in your soil using soil moisture probes so you can reliably assess how much water is available to your trees. After you’re finished with your regulated deficit irrigation, you can check your soil moisture status to ensure your trees are hydrated for harvest.

UI-Screenshot_Soil-Moisture

3. Plant stress monitoring: Knowing exactly how much stress your trees are under and for how long helps you prevent causing long-term damage. Semios uses dendrometers that provide a maximum daily shrinkage (MDS) reading so you have real-time information on the stress level of your trees.

UI-Screenshot_Plant-Stress

Have questions about your irrigation strategy & how Semios can help?
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