AlmondBeat #3 2025: Managing Stress During Nut Fill

Information provided by Matt Brocato, Phytech Customer Success Manager

Welcome to AlmondBeat #3, where we share timely agronomic recommendations to help you get the most out of your season.

From mid-April through the end of June, almond trees enter a critical phase known as nut fill, when nuts are actively sizing and developing inside the shell. Right now, almonds are in Stage 2 of nut development, where we see kernel growth. 

Any stress during this period can directly affect final kernel weight and overall yield. The goal is to keep trees as stress-free as possible heading into the heat of summer.

Every grower approaches irrigation differently, depending on various constraints: limited infrastructure output, labor availability, or overall water supply. No matter the system, understanding what’s happening in the orchard during this phase is essential to minimizing plant stress and protecting your yield.

Managing Stress at the End of Nut Fill and After

As we move into late June and early July, a high priority is managing heat stress, especially when temperatures can be at their highest. It’s important to stay ahead of the heat. If a major hot day is coming, pre-irrigating can help trees adjust and avoid some of the stress. Having moisture in the root zone ahead of time helps trees cope better and reduces the shock of extreme temperatures.

If pre-irrigating isn’t an option, the next best thing would be irrigating on those hot days. The main thing is that you want water to be available to the trees during this time. This is essentially why we push pulse irrigation and higher irrigation frequency.

Rather than running a 24-hour irrigation set once a week, where trees start the week with a lot of water and then run low by the end, we aim to keep water applications more frequent, so trees don’t go through dry spells. That drop in availability can cause stress, even if you’re putting out the same total volume of water.

Keeping the root zone consistently moist, but not saturated, can make a huge difference in how well trees tolerate summer conditions. This will influence how much energy they can keep putting toward nut development, which is what we’re after.

Final Push for Nutrition

Fertilizer needs also peak during this window. Most nitrogen uptake happens by late June, so it’s important to make sure trees have what they need before that cutoff.

Avoid heavy nitrogen applications after June. Excess nitrogen post-nut fill can increase the risk of hull rot later on, especially as we transition into hull split. That’s why this period is often the final push for nutrition before shifting focus.

The goal is to keep fertility in balance. It should be enough to support kernel fill, but not so much that you’re setting up problems down the road. 

Prepping for Hull Split with RDI 

Once nut fill ends, we transition into hull split. Hull rot becomes a concern in late July, especially if trees are too wet. Regulated Deficit Irrigation (RDI) can begin now to do several things: 

1. Save on water

2. Minimize hull rot risk

3. Accelerate hull split once it begins

This needs to be managed carefully, though, with monitoring. Too much stress can have negative effects on yield for both this year and next year. Over-stress now can lower kernel weight, giving lower yields. It can also limit next year’s crop potential if trees see high stress depleting their strength.

This is the time for precision. Pay close attention to tree and soil moisture conditions, and make sure RDI is supporting (not compromising) long-term productivity.

For more in-season tips and support, look out for the next AlmondBeat. We’re here to help you make the most informed decisions for your orchard.