2026: Earlier Almond Irrigation Start Revisited

Apr 8

Apr 8 2026: Earlier Almond Irrigation Start Revisited

Dr. Or Sperling (ARO-Volcani) and Zac Ellis (OFI) discuss the exciting 2025 results from their proactive irrigation scheduling application in California almond orchards.

You can ask questions and provide feedback to the researchers at:

Or Sperling: orsp@agri.gov.il or +972 52 6278189

Zac Ellis: Zac.ellis@ofi.com (559) 303-0599

Maciej Zwieniecki: mzwienie@ucdavis.edu

Come to an upcoming extension meeting!

In the San Joaquin Valley:

UC Cooperative extension has a Regenerative Almond Orchard Field Day on Tuesday, April 21st at the UC Merced Experimental smart farm

The Almond Board of California also has four upcoming IPM meetings, tackling rodents, red leaf blotch, Carpophilus and other pests:

Ceres: Wednesday April 22

Durham: Thursday April 23

Fresno: Tuesday April 28

And Bakersfield: Thursday, April 30

And finally Wednesday, June 16, if you’re an almond variety nerd like me you can’t miss the Almond Board’s Crackout Event at Merced College

In the Sacramento Valley we have a Third Thursday: Nematode Management in Orchards meeting in Orland on April 16 from 11-1

Nickels Field Day is Tuesday, May 19 in Arbuckle

I have two almond variety meetings at the Chico State Farm in June. Thursday June 11 and Thursday, June 25th.

The Third Thursday on July 16 will be in Yuba City and cover Walnut Mold

The Third Thursday on August 20 will be in Orland and tackle labor economics

Following a harvest season hiatus, there will be a Third Thursday on November 19 in Yuba City recapping 2026’s IPM challenges and lessons

The views, thoughts, and opinions expressed are the speaker’s own and do not represent the views, thoughts, and opinions of the University of California. The material and information presented here is for general information purposes only. The "University of California" name and all forms and abbreviations are the property of its owner and its use does not imply endorsement of or opposition to any specific organization, product, or service.

Thank you to the Almond, Pistachio, Prune, and Walnut Boards of California for their kind donations. Thank you to Muriel Gordon for the music.

Earlier Almond Irrigation Start 2026

Luke: [00:00:00] There are numerous upcoming Orchard education meetings to take note of in the San Joaquin Valley. Uc Cooperative extension has a regenerative almond Orchard Field Day on Tuesday, April 21st at the uc, Merced Experimental Farm.

The Am Amen. Board of California also has four upcoming IPM meetings, tackling rodents, redleaf, blotch, carpools, and other pests Ceres. Wednesday, April 22nd, durham Thursday, April 23rd, Fresno, Tuesday, April 28, and Bakersfield Thursday, April 30, and finally Wednesday, June 16. If you are an Amman variety nerd like me, you can't miss the Amman Boards crack Out event at Merced College

in the Sacramento Valley. We have a third Thursday Nematode Management in Orchards meeting in Orland. On April 16 from 11 to one. Nichols Field Day is Tuesday, may 19 in Arbuckle. I have two [00:01:00] almond. Variety meetings at the Chico State Farm in June, Thursday. It. June 11 and Thursday, June 25. The third Thursday on July 16 will be in Yuba City and cover walnut mold. The third Thursday on August 20 will be in Orland and tackle labor economics. Following a harvest season hiatus.

There will be a third Thursday on November 19 in Yuba City recapping 2026's IPM challenges and lessons.

Today on Growing the Valley Podcast, I am back again after one year to talk about an earlier start to irrigation in almonds, a different approach,to irrigation in almonds. And once again, I am joined by Dr. Or Sperling. and then instead of maciej zwieniecki at uc Davis, we're joined by Zac. Zac, what is your title at Olam?

Zac: I am senior Director of Agronomy at Olam. Food [00:02:00] Ingredients.

Luke: Excellent. And then, Or remind us of your,title. You were, here, I believe on a sabbatical. but you're back in Israel now.

Or: And I'm a scientist for the Israeli, ministry of Agriculture.

Luke: Yeah. And special thanks to, Or, speaking to us, , from a war zone currently.

Thoughts and prayers, , with him and his family thank you for, for taking the time and, and fitting us in. Or could you remind us what your elevator speech is describing this novel approach , to irrigation In almonds,

Or: I see it as the shift from being active to proactive .

Irrigation applications before we had these glimpses of data sometime from smaller industries, like which I work with in Israel. And then we had to find tools to monitor the trees and then if we sense that they're not in optimal conditions, find ways to respond . But with the massive amounts of data that now we have collected, [00:03:00] and especially with working with Zac and and Olam , we were able. To, characterize what is the water requirements of almond trees , in high production and then plan the irrigation moving forward. So essentially budget the water. So it's this shift , from reactive, which is whatever I was doing, having , many sensors and having models of, I say transient use of, water by trees to knowing what the trees would need to maintain, maximal production and sustained growth , and reproduction , for the, foreseeable future.

Luke: Very interesting kind of , providing a resource, even before , the tree has asked you that, it's deficient , or it needs it, it's already, if already on hand,

Or: if I can give a metaphor. We're now at home, so,, because of the war, so therefore there's the kids and you have to feed them [00:04:00] throughout the day and you shouldn't wait for them to be very hungry or complain about their hunger.

You need to. plan , the diet , for today and for tomorrow, Apparently they eat so many meals, these kids, and that's your approach. So it's a very proactive approach. You're making sure that , the diet is there for them to grow and study.

so you should do the same thing when you're growing trees.

Luke: I love that analogy Or. Now, Zac, were you irrigating with this more reactive approach as the classic approach that everyone was using previously? How both were you deciding when to start the irrigation season in your almond blocks, as well as how were you deciding on those irrigation decisions, subsequently throughout the season?

Zac: Yeah, we were. Certainly irrigating, like most of the industry, irrigates in a much more reactive manner. and Or is very right. , As a grower we come into the season, we know we have stored soil moisture that we can [00:05:00] use, going into the season, but, , and to some degree we account for it, but I don't think that we. Rely on trying to, keep some of that in reserve throughout the season. Typically what we'll do is , we'll burn through that stored soil moisture from the spring, , whatever it is, irrigation or precipitation, effective rainfall. Then we'll start to irrigate and we use, all of the different state-of-the-art sensors, namely dendrometers and capacitance soil probes and,pressure transducers to understand where we're watering. And we really let those sensors tell us, you know, that we've emptied the reservoir and that it's ready to fill it back up. But that's traditionally gotten us in situations where, because of, , the number of sets and the number of irrigation, blocks that we have, or, just transient deficiency, because we have, , drop conditions or a well goes down, we end up having issues where.[00:06:00]

We don't have enough buffer and we pay the price and, reduced growth , and stress. So that this was the way that we were doing it. We were reacting more with irrigation frequency and using, , , a reference of apo transpiration in , a predetermined crop coefficient that everyone uses and scheduling water that way once we ran it through all of that storage soil moisture from the spring and winter.

so that's,, when initially we had looked at this, we thought that irrigation frequency would be able to solve a lot of these problems, but we found out that really, it is good , and we found a lot of efficiencies out of increasing frequency. But we also would get closer and closer to that line of stress as a result.

And, if we missed one irrigation, we didn't have anything in the soil to help. Bail us out until we could get the irrigation back on for whatever reason.

Luke: Yeah, it does seem that way in [00:07:00] the classic way of farming almonds, that you start with this buffer, but by the midseason you are really farming, just that, that top foot or top two feet, it's a very narrow, band , of moisture that you have to work with a very minimal, bank.

Zac: Yes, I agree.

Luke: Then Zac, this was mentioned by Or last year, in the interview, but remind us what led you to connecting with Or, and working with him and Maciej at uc Davis to develop this alternative approach?

Zac: Yeah, it's very serendipitous. I've been in production ag for the last 10 years with Olam in this position.

Been farming for about 20 years now, almonds. and went to graduate school at Fresno State about eight years ago. Swore I'd never go back to school. Said I'm going into production. I've, learned enough and I'm ready for the real world. but yet here I come back eight years later , [00:08:00] and, , just the curiosity that I have and, and the opportunity that Olam gave me to help, support me through going back to school.

I decided to, to come back and get my PhD. So, worked with a lot of different professors as a grower collaborator in the past, and so I had a lot of. Network already. and Maciej was one of those people that I've been working with through the Carbohydrate Observatory for years now, since day one, really?

And, thought, Hey, this is a great opportunity. I'm gonna come , and learn from the best. And unbeknownst to me Or was coming here on sabbatical and,. , he was here and , he was looking at all this data that I've been sharing with Maciej for years and I've been gathering for a long time without really understanding or knowing what I should do with all of this data. A little overwhelmed, to be quite frank, uh, but, Or came along and he said, Hey, I have to meet this guy Zac. He's got all this data. I need to, need to learn more. And, and, we met and immediately I knew that Or. Was gonna change my trajectory, for my education and for my career. , [00:09:00] And, , just made a really, really good friend, and collaborator.

So from there we, we kind of hit it off and started gathering data and just getting together weekly and just talking through a lot of these different problems that I'm seeing and that, you know, that, that, that may be useful. , And I think through a lot of those conversations with him and Maciej .

other professors at uc Davis, we've, you know, we've come up with some really cool, innovative ways , of tackling a rather complicated thing nowadays, which is, you know, irrigation, scheduling, and almonds.

Luke: That's a great story of the connection there with, all the way from a really nerdy, professor at uc Davis, like Maciej , down to the boots on the ground in farming. When I go to other countries, I just find that there is like no connection between. Agriculture, academia, and the actual farmers.

So , that's a really fantastic story.

Zac: Yeah, , it's really good. And you're right, I mean, [00:10:00] is. One of the smartest people I've ever met in my life. One of the smartest plant physiologists in the world. And when you get his mind thinking the way that growers are thinking, and you start gearing him that way, I think that all of us have a lot to, , get advantage from , and, and get some value from, when that happens. So I'm just happy that we're able to get together and. Look at this data in a meaningful way and hopefully create real world solutions. And, , this irrigation scheduling app that we'll talk about , and, this method I think are gonna be a really useful thing for growers in the valley.

Luke: Excellent. And you've queued that up nicely for us. So after all of these discussions , and iterating. Back and forth with, Or, and Maciej , what did implementing this alternative, proactive approach look like for you and Olam in 2025?

Zac: one when we looked at this approach, what I liked the most about it was that we weren't applying more water than what I normally apply.

So there wasn't this. , [00:11:00] This agenda of like, okay, well how much water do we apply? We're saying, no, , we're gonna apply the same amount of water as a normal, high producing orchard wood, but we're gonna do it in a different method. And, really what it came down to for us in the field was just starting irrigation earlier, being like, Or said more proactive about.

Irrigation. and what that meant was that instead of waiting until, you know, usually April, sometimes,, like 2023, it was May when we started the irrigation pumps. we start in March, , the beginning of March we're putting on irrigation. And it's just one of those things , that, uh. You think, okay, well we'll start the water a little earlier. But really from a logistics and operation standpoint, we are very busy after harvest, preparing for bloom, doing a number of different things, and we usually go right up to like, to bloom. And then once we get into Bloom, , we've got all these other things and typically after, that's when we start fixing irrigation lines and getting prepared for , [00:12:00] the season.

But now, , operationally we need to plan some of those repairs , and maintain some of the irrigation system earlier so that we're ready to irrigate in March. so fundamentally, starting earlier, was a big difference and something that we had to. Allow for it in terms of , our operational schedule and the logistics around all the different things. But then, you know, what was really interesting is that when we started doing this, And we have all these dendrometers , and soil sensors in the field. We just never got to a point where we were diminished enough to see a whole lot of stress. And it was very obvious in the beginning, that we just didn't see the type of stress., And when we measure stress, it's an MDS, it's a, maximum daily shrink or swell dendrometers. We measure those and we just couldn't get the same kind of stress that we did, with the grower standard method, which is waiting until we've kind of blown through most of that stored soil [00:13:00] moisture and then reacting to, the drought stress conditions that we have, as it starts to heat up.

So we just didn't see that. And then we really didn't see it in sensitive varieties like Monterey, We saw an immense improvement in the Monterey growth and an immense reduction in stress, specifically for that variety

those were two main, observations. The final one was that because of the way that we're irrigating, we have more of a static crop coefficient. We're not chasing this crop coefficient, we're measuring it through using, remote sensing and then using that as our benchmark. It was a really easy glide path into deficit irrigation.

So what I mean by that is that , the trees just seem to be able to pull the water down enough. Because during the hotter part of the season, the crop coefficient that you typically would use [00:14:00] is higher than what you'll typically get with this method. And because of that, , there were periods where we were putting on less than what ET was calling for that week, but because we had stored up so much soil, moisture was eating into that and it was gradually drying that soil , and creating a condition that just.

Really helped us at harvest and create a uniformity, reduced hull rot, a lot less bark slipping. It really conditioned the trees, for harvest. Well,

Luke: yeah, that was gonna be my next follow up was whether that dry down for hull split, was more challenging. But it sounds like it was actually easier and you saw some immediate benefits there.

Zac: Yeah, because essentially you're flipping, you're getting aggressive with your irrigations early in the season when there's this period of grand growth, , in April and May. But as it gets really hot, you're applying less than what the weekly ET is. But because you've stored that soil moisture, there's moisture there.

It's just at a diminishing [00:15:00] rate. So it just, it allows more control for soil moisture, and subsequently controlling the tree's Stress.

Luke: Did you feel like at looking at the trees with providing that proactive irrigation starting in early March, that you saw more vegetative growth than you had in previous seasons? Or was that too hard to tell?

Zac: You know, we didn't really measure that, but it didn't appear that we had a ton more like. Additional growth. , I think it was all proleptic, growth that will be viable for next year. And that's really gonna help us, you know, for this 2026 season. But I don't know if it was enough to see like a noticeable difference, visually. ,

Or: Well, Maciej did and used the NDVI data again for this year, and he had some results about this.

So in terms of, remote sensing, it was possible to see, that these trees had sort of, up their game in terms of NDVI this [00:16:00] year

Luke: as a measure of just kind of a canopy health or, actual canopy size.

Or: Well, that's NDVI and Zac. Has a lot of works about what that actually means in field conditions.

But the way we have been using this, and also compare this to data that Bruce Lampinen gave us is, so it's, it, it is comparable with light interception.

Luke: Okay. But the main benefit there, Zac, was that you didn't see those stress periods that you were trying to avoid.

Zac: , Or spot on.

I think from a remote sensing perspective, there was signal that we could pick up on. But from a visual perspective, it's hard to ascertain whether there's more or less growth. But, , certainly less stress. And when you look at the, the, you know, lateral growth the trunk growth that we were seeing from the dendrometers, there was a huge difference in, in that type of growth.

So, Hard, hard to see things visually, but with these instrumentation, , that we have remote sensing, proximal sensing, and even some of [00:17:00] this, some of these more direct measurements, we were able to show that there's added growth and less stress, using , this more proactive method .

Luke: Typically with irrigation studies, you don't really see any yield impacts in the first year. These are multi-year systems. You're creating the floral buds for 2026 in this case. And, but did you feel like there was, any impact there on yields or kernel size? Anything at all?

Zac: No, what I can say is that, , so from going from 2024 to 2025, we had a tough year. We had some turnout issues and I'm sure the audience is aware of, some of these issues that happened in 2025 with just lower turnouts. And so we were affected by that as well.

We had a worse off year in 25, as we did in 24 at that ranch. But what I can say is the losses experienced in the treated were significantly less than what we saw in the untreated or the grower standard. I think really the main driver will be this year's yields to see what happens and [00:18:00] see how, last year's growth is really gonna present this year.

Luke: That is, it's usually the subsequent season that you start to see either benefits or, detrimental effects of something that happened, the previous season, Or what did you feel like you learned from the 2025 season and what were any changes that you made to this program headed into this 2026 season?

Or: So I learned one thing , and it is that simple work. So the way we have designed this system is that it is very easy to implement since you can, you get the irrigation schedule back in March and it works. So whatever , you work with the farmer and the irrigation guidelines you give them, they're very easy to implement.

The other one was, we did have some open questions, and then Zac challenged every one of these. And I think what we dealt with the most was, our assumptions about how much water [00:19:00] storage there is actually available for the trees and , what's the amounts of storage that we should use the budgets with.

And it really changes depending on for once and you know this from California. And then the same goes for Israel where we grow almonds in places where it rains. Nicely. And then in some other places where it rains very little. I knew that, but I wasn't aware of how sometimes, a 50 inches, of irrigation is exactly the same as a 30 inch irrigation.

It's just that there is so much variability in the available water from, from winter. so that is something that we worked on. But then, it pretty depends on the soil type and on the canopy size, we just realized, and we're still thinking of how to implement this, of what is the amount of rain that you should actually, use in your budgeting moving [00:20:00] forward.

that is where most of the learning was this year. 'cause there is so much about the budgeting that relies on these climatic conditions and what happened in the winter. In fact, in your interview the last time we said that one of the questions that this approach answers to is climate variability, , we used to have very similar irrigation guidelines because we always focused on the summer, but we knew that the winters are very different. so we had this as a very important base for this irrigation approach but then I don't think we were aware of how many more variables are into this, storage budget.

Luke: Zac, do you have anything to add to that?

Zac: Yeah, that was really the focus was effective rainfall. And then, , that gets us talking about rooting zone and, and , where the roots are, extracting [00:21:00] water and age and all of that. That was really the main thing that we've learned in our working on right now. it's certainly gonna be interesting this year considering the advanced heat and how that's playing a role. And we're already seeing some advantages from being proactive, even, in a, a year like this when it's hot. But what we've really learned is that if you can stay ahead , of these stress events and create some buffer in the soil and try to maintain some of that stored soil moisture deeper into the profile throughout the season, you get a lot of benefit and, the one question that we have moving into 2026, I think, is really around some frequency questions as well of like, as a grower who's trying to be innovative and has been, , in , this wonderful position at Olam to be able to do some of these cool things. We're well resourced. We irrigate very frequently and we, we believe strongly that more frequency in spreading the water over the week is better. And that , it reduces the amount of [00:22:00] stress. but when you come to this approach, you're essentially doing the same thing through, through the soil as a medium, more than frequency. And there's a ton of benefit to that. So we'd like to compare the two and just see, , this field water balance approach if we did this versus a higher frequency irrigation. Is there any added benefit in doing a high frequency irrigation, type of approach that's traditionally surrounded by, , using the soil water early in the season and then getting on a very high cadence of irrigation, frequency versus this approach where we're really pushing water early , and building the profile.

so we want to implement that. and then also move this up to the more northern ranches that we have in the Central Valley. So the Madera region, Chowchilla region. We're gonna move it up there and, with more rainfall, this effective rainfall , and soil, physics and conductance. And these things are really, need to be thought through , and we want to start testing some of that.

Luke: Got it. And Zac, you've already noted [00:23:00] that, you started irrigating in 2026 here in early March. we are recording this in late March, and, , those early irrigations, proved, really prudent, with the heat. We didn't know that we were going to be getting so early in the season, but do you have any other notes on. How you're planning to irrigate the rest of the 2026 season. What does this actually look like? Are you going to a website? Can you kind of walk us through , what that looks like as you make irrigation decisions?

Zac: there's a great site that, that Or and Maciej and myself and, and Nicolo have, we've all worked on , and, you can really just point on where your ranch is , and put some information around how much water you've applied in the winter time , and when you wanna start your irrigations.

If you have an allocation you can put in that, and then you hit that button , and run the system and , it, it gives you a great schedule. So we did that like any other grower would at the beginning of the season. and we kind of have a [00:24:00] playbook now for the , whole year. So far it's worked out, like you said, really well this year because we were ahead of the curve. , The, the heat came, the untreated, really, really took a hit, at first because we couldn't get around to all the orchards, as quickly as we wanted. , And so there was , some higher MDS already early , this, this growing season. And so I think this will show even more of a benefit when you have unseasonably warm years like this.

Luke: Absolutely. That makes a lot of sense. And. As Or was noting earlier, rainfall is such a tricky component both to model and I've always thought that deciding when to irrigate, especially early in the season, is just so much trickier up where I am in the northern Sacramento valley 'cause we have the rainfall plus we tend to have some heavier soils compared to maybe a sandy soil, a coarse soil down in Kern County with minimal rainfall. So I'm glad you guys are continuing to [00:25:00] improve the functionality there,

Or: but also when you work with the app. Zac was saying, so you type in some general information and basically what you do is , with a Google map you select the exact location of your form because then it takes this NDVI component and then tells you what's the potential for transpiration for your field. But then there is all of these sliders that you can move back and forth, and see what would be the effect. If you did so and so and there is also this graph that Maciej design that would turn to red, or actually if you're in deficit or if you're over irrigating very early in the season and probably losing water , for deeper collation. In this case you can also move , the slider back and forth in terms of when to start the irrigation and doing this. And this was very interesting to us. We were always able to see how farther up north, You actually, when you move the slider to April or even to May, the budgeting sort of suggests [00:26:00] that you're not gonna see any stress, which you cannot do down south. and these are things that we knew , from experience and from farmers and from talking to you. But the budgeting does, project this as well.

I think if users before they just, of course there is a, chart that tells them, month by month irrigation amounts, but there is so many things that they can change and fix it to what they consider is optimal.

Luke: Got it. Yeah, we're recording this on the 25th of March, but even here in, in the north in Butte County, I would've, started irrigating at least mid-March. We had so much heat and yes,, there's soil moisture. But, after our conversation last year, I am all for, , maintaining that bank. My previous research , led by Ken Shackle with deciding to start the irrigation season with the pressure [00:27:00] bomb and exactly that reactive approach that we started talking about. It was clearly too late by the time we had these various triggers, with the pressure chamber,/ pressure bomb. And these entries just dry down so fast once you really start, drying up that bank. So I love this proactive approach , that you've both developed with Maciej .

Anything else , from either of you on either plans or other thoughts before we wrap?

Zac: , I'm, happy to answer any questions if anyone has any questions about this irrigation method and how to implement it. If anyone is interested, they can reach out to me and I'll give my information.

We can put it in the notes.

Or: Same here. , I'm , fully committed , to the farmers, so you should, have our contacts and then , anyone with any question or needing for any guidance on how to use this and of course thoughts of how we should improve this. that would be really appreciated.

Luke: I will include, your contact information, for both of you in [00:28:00] the show notes, and the link to the program is pisa- ca.org, so that's pisa-ca.org and we will also include that link in the show notes as well. It's certainly, too late in , the season to have started irrigating in early March if you haven't already, but still something that you can play around with that tool, here in 2026 and, Perhaps, learn what that tool provides, and, ask questions and provide feedback for Zac and Or so, I want to thank you both so much.

Zac: Yeah. And one side note, Luke, just to clarify, you can on the app. Fill in previous irrigations for previous months. So even if you've already started irrigations, you can put that information into the Pisa California app and it will still calculate what's to come and what you should expect so I think there's still some utility even this season right now [00:29:00] for growers

Or: it uses up to date weather, so whatever has transpired, it's in there and any suggestion it makes for the future would try and account for this.

Luke: Excellent. I am just so excited about this approach and I look forward to, getting, connected again, after this 20, 26 season.

And I'm hoping to hear, more excellent, results, on your ranch there, Zac.

Zac: Thank you, Luke. I appreciate you giving us the time and platform to talk about it. hopefully we'll have an update next season for you.

Luke: Excellent. And again, stay safe Or, and I hope this conflict is over very soon.

Or: Thank you. Thank you so much.

Apr 8 2026: Earlier Almond Irrigation Start Revisited

Apr 6 Encore: Earlier Irrigation Start in Almond