191: CropManage: Improving the Precision of Water and Fertilizer Inputs

Looking for a tool to help you make irrigation and Nitrogen application decisions? How about one that will not cost you anything? Michael Cahn, Farm Advisor, Irrigation and Water Resources at the University of California Cooperative Extension in Monterey County explains a valuable software for farmers – CropManage. This free software from the University of California combines a wide variety of data inputs to help growers make accurate and timely irrigation and fertilization decisions based on crop-specific models. The tool aggregates data from the University of California at Davis Soil Web, weather stations, evapotranspiration, and satellite imagery. Plus, it can be integrated with a farmer’s existing software.

CropManage has been ground-truthed in more than 30 field trials. While the product started in lettuce, it has expanded into vineyards. Your vineyard can be a beta tester to help improve this software for the wine industry.


Vineyard Team Programs:

Get More

Subscribe wherever you listen so you never miss an episode on the latest science and research with the Sustainable Winegrowing Podcast. Since 1994, Vineyard Team has been your resource for workshops and field demonstrations, research, and events dedicated to the stewardship of our natural resources.

Learn more at  


Craig Macmillan  0:00 

Our guest today is Michael Cahn. He is Farm Adviser in irrigation and water resources with UC Cooperative Extension Monterey County. But he also works in other counties as well, as I'm sure we'll talk about. And today we're going to talk about a system a decision assistance system for a whole variety of crops called CropManage, which is free and available online. And I've been following for quite a few years. In fact, he was a speaker at one of our Sustainable Ag Expos a few years back, and at the time, I was like, this is the coolest thing ever. And I can't wait to see how it develops. Welcome.


Michael Cahn  0:29 

Well, thank you for inviting me.


Craig Macmillan  0:31 

So first of all, what exactly is CropManage? Well, it


Michael Cahn  0:35 

is an online decision support tool that's sort of in a nutshell is how we describe it. It's essentially software that takes information from different sources, puts it through some crop models, and provide some recommendations on how long to irrigate your crops. It also for a number of crops, provides decision support on nitrogen management.


Craig Macmillan  1:03 

How did this all come about? This was a really interesting project, there's a lot that goes into it, what was the genesis, the idea behind this?


Michael Cahn  1:09 

The start of CropManage was in lettuce a number of years ago, we're trying to help growers be more efficient in nitrogen management. Nitrogen, as most of you know, in its mineral form, which would be mostly nitrate, is very mobile in the soil. So it seems like if we're going to manage nitrogen accurately, then we also have to manage water. So they go to hand in hand in hand. Of course, I work in irrigation water management. So I also had the interest in just using water efficiently on the Central Coast, because of our limited water supplies. You know, we could use nutrients more efficiently and water more efficiently if we had some sort of decision support tool. When I started working with the vegetable growers. I often asked them, you know, how are you making decisions on irrigation? How long to irrigate when to irrigate? And you get a variety of answers. But essentially, it came down to the experience of branch managers in irrigation farming, sort of passing that information down from one irrigator to another irrigator. One farm manager do another farm manager. And by the way, this happens at vineyards too, you know, so the question was, well, okay, are they you're getting efficiently. And so, as I started out as a farm advisor, my first question was, how do we measure how much water we apply, you have to remember back when I started, wasn't so easy. The flow meters we had available for these propeller meters, they're often inaccurate. And then to record derogations, there was no output, you couldn't hook them up to a little computer or data logger. So that came later. But once they did start monitoring water use growers, who found that if you base it on crop ET, they're putting on 200, 300% of crop at the estimate. And so, so the question was, who's right, you know, is the crop ET right or are they right? So then we start doing trials, saying, well, let's just follow this crop ET and see if that would work. It worked, you know, we never reduced yields in lettuce. So we kept the soil still with adequate moisture. At that time, it was like a spreadsheet model that we used. At the same time, we were working on nitrogen management using the soil nitrate quick test to evaluate mineral island in the soil.


How are you measuring Crop ET back then? We're estimating it, I should say.


Yeah, it's still the same way as we do it and CropManage, we developed crop coefficients. And that was a big question of growers, what is my crop coefficient, and there seemed to be a misunderstanding of that, because they thought it was one number like point seven, one, and then you use that with the referencing ET value that comes from usually a CIMIS station that California irrigation management information system. Well, it's not one number. It's based on really the fractional cover over the ground. So how much of the ground is shade by the use in in lettuce? This changes tremendously, you know, over a season, it goes from essentially no cover to full cover to about 90%. And so then the question was, okay, no cover here, but I need to irrigate Right. So we do have water loss from the soil by evaporation. So we have to model that too. So that all goes into the crop coefficient calculation. And we have that in our spreadsheet model. We based it on published work that was done in the Silicon Valley by my predecessor, and other people, that model worked fine. So it wasn't a model, I necessarily came up with the innovation was just trying it out. And validating it. That's what we did, then, you know, we got grower interest. They said, Yeah, we'd like to use this type of model for water management. We also were interested in nitrogen management using the soil nitrate quick test. And so another aspect to what we did was look at, well, how much nitrogen does a lettuce crop need as you go through the season, and we did this by brute force by harvesting lettuce at different stages, and analyzing how much nitrogen was in the above ground biomass. And that gave us the demand side of the equation. So so now we want to put it all together, and the grower interest was there. So we realized, you know, if a grower was going to use this spreadsheet, it would be a little cumbersome, because think about how many separate plantings there are on our ranch, lots of them. That's a lot of spreadsheets to keep track of. So we wanted it to be in a sense a database database that we available to a grower online. So that was the idea that we have a web based decision support tool, so it holds all the data. So once you enter it, you don't have to re enter it. There is some upfront cost and time when setting up your farm or ranch on CropManage. But once it's set up, only if you make modifications do you have to enter anything.


Craig Macmillan  7:01 

Now there's a lot of inputs that go into this, I was looking at the landing page for the CropManage Site, can you tell us a little bit about all of the different parts and pieces of data and information that go into into the system?


Michael Cahn  7:08 

Essentially, you're giving crop manage some information about your ranch. So all the different fields that you have, we need to be able to refer to them. So you set that out, and you associate a soil type with that, because we do have models of water holding capacity in the soil. It's based on the soil texture. Now because it is web based, we can use other tools to help you set this up. So fact crop manage links to UC Davis soil web. So you click on a Google map, find your field, you click on it and the soil type comes up, you can always modify the values there. But we bring those in, you don't have to know to use CropManage, you have to associate CropManage with some weather data. So there's the option to use the near CIMIS weather station, you can use multiple CIMIS weather stations, there's a spatial CIMIS option, which is a hybrid of satellite and weather stations. So it brings in the referencing ET data will also bring in rainfall data from the CIMIS station. Because we are working with fertilizers, you can make a customized list of the typical fertilizers that would be used at that branch. And so there is a list there. You can choose from, you can enter your own specific fertilizers that you use. Also, you'll see a place where you set up your commodity lists. No sense in having information pop up about lettuce if you don't grow lettuce.


Craig Macmillan  8:52 

Exactly. And vineyards are part of the system now. Is that right?


Michael Cahn  8:57 

That's right. They're in the experimental phase. And if you want to activate it, you'll see in your profile place where you check experimental commodities. And that's because we're still developing the nitrogen model for vineyards. So it's good to use for irrigation management, not put to use, for nitrogen management. We're working with other UC Davis specialists on the nitrogen.


Craig Macmillan  9:22 

You're gonna have a hard time with that. Trying to get a handle on the demand side of nitrogen for vineyard stuff. I've worked on that as a as a writer. And yeah, that's that that's gonna take some work, but I'm glad that it's part of the idea. I think it's super important. I think it's something that people have overlooked. I think we've been flying blind as far as nitrogen and vineyards goes, we've gotten better in the irrigation side.


Michael Cahn  9:45 

Right, right. And that's what I'm learning is the vineyard people have no agreement on a lot of these things. One of the things one of the purposes of crop damages. Well, first pivotal is public, right? It's developed by the University, it takes our science and tries to make it more available to practitioners by having the decision support models are based on our research. And as we do research, we can update these models, but also, as practitioners use crop damage, they can tell us we oh, this doesn't work, right, you know, you need to investigate X or Y. And so for developing new hypotheses or directions in our research, it's useful that way, too. So it's a two way street, I should say.


Craig Macmillan  10:44 

How is this going with adoption? Why is it how's it going with communication from growers back to you? Are people picking this up? Are they giving you back the kind of feedback that you need on the growers side, how can we help you?


Michael Cahn  10:55 

So for the vegetables, it's getting adopted by growers that are ready to really implement better water and nutrient management, not saying all growers adopting CropManage, but we do have growers who, and some growers, they're saying, Yeah, this is the direction we want to go. And they're in the phase of figuring out how to get it adopted on their growing operation. Because it's one thing where someone at the top or management wants to adopt it to another thing to get your irrigators to adopt it. So that's the hardest part. And then the same with the strawberries. In some ways we've been even more successful were, they were the strawberries. And then in vineyards, while we're, you know, in the beginning stages here. And so right now, what we've been doing is we have beta testers, essentially, vineyard growers that are saying, Yeah, I'm interested, what we do is we put a flow meter on a block in their vineyard. And one of the nice things about crop manages, it can take sensor data into it, just like a lot of those tools out there that are sold to, to vineyard people for soil moisture monitoring, we can also bring soil moisture, data flow meter data in you can observe it and crop manage. So we've outfitted a few vineyards in the Salinas Valley with that, and some in the Central Valley to see what CropManage estimates and terms of water use and what growers are putting on. 


Craig Macmillan  12:39 

Yeah, and if they tell me a little bit more about the one thing that I love about CropMnage, it's science based. And it's also ground truth. So as you've gone along, you've you've done the background work you've come up with, Okay, this looks like something that would work in terms of figuring out Kc and things like that. But then you actually have spent the time and the energy and whatnot to actually ground truth of the decision assistance model against reality, right?


Michael Cahn  13:05 

Yeah, we haven't done vineyards in the way I would love to do it, which is not just compared to what a grower standard practices, but go beyond that, where we have some pre arranged treatments in compared to those treatments. So for example, vegetables, we've done replicated field trials, seeing broccoli, where we apply 50 7500 and 125 and 150% of the recommendation, then evaluate the yield. Like to do this in vineyards, that is trickier. It's a perennial crop, so you'd have to run it for several years, really, to see, you know, really what the outcome is.


Craig Macmillan  13:50 

You have other variables along the way things like crop management or dropping crop they're changing cropping styles through pruning and whatnot, year to year during canopy management. I found that to be particularly tricky. If you're thinking about idea of percent cover. If you've got a California sprawl and everything's flopping all over the place then works. You push everything upright. And now you don't have as much shade, but you still have the same amount of leaves. So doing those kinds of estimates is tough. Yeah, definitely. It's on the fly. But I believe he can do it. I believe in you.


Michael Cahn  14:23 

Well, we'll see. Maybe beyond my career, but someone needs to do it.


Craig Macmillan  14:30 

Do you still need beta testers?


Michael Cahn  14:32 

Sure. Yes. Because the more feedback we get, the better and there's different levels of they could do for the most intensive is where we put you know, a flow meter on and some soil moisture sensors. They want that in the field, and then they can follow, you know, how much water they're putting on. And what this means in terms of soil moisture, what CropManaged recommends We also take canopy photos, to adjust the canopy curve for how they're managing the vineyard. We also import automatically satellite estimates of canopy that comes from a NASA product called SIMIS satellite irrigation management system.


Craig Macmillan  15:20 

Which is really cool, by the way.


Michael Cahn  15:22 

Yeah. And this year seems pretty accurate, you know, very close to our estimates with ground truth, measurements of canopy. And that's going to be compared with opening ET, which is a satellite based estimate of ET, actual ET again, the nice thing about these web based tools is you, the user don't have to go to all those different websites, we can bring that data in automatically in the parts we need for your decision support, we just pull that out, you don't have to search through different places in websites to get what you want.


Craig Macmillan  16:00 

Yeah, I like the way the system is, or the way the interface is structured. It's a great dashboard. It's easy to navigate around, it gives you great information easily, which is wonderful. I think I already know the answer to this question. But what would you say is the number one advantage, or the number one benefit to a grower, no matter who they are, of using CropManage?


Michael Cahn  16:23 

I guess the number one benefit is they have a better understanding of really the water and the nitrogen management over a whole season, just at their fingertips. For perennial crops, you can see what you did year to year. So the record keeping, I would say, is a big benefit. Even if you don't follow any of the recommendations, just keeping records is extremely useful.


Craig Macmillan  16:49 

Measure to manage.


Michael Cahn  16:50 

Yeah, it's been very useful for me, in my research, it's like I built this mostly out of self interest in the sense. You can imagine if you were trying to help people doing irrigation, you need to know how much water they're applaying. And so here we have a tool where I can give them feedback right away, how much water they're applying, I used to have to calculate all those ET measurements, or estimates by hand. Well, this software does it. So it's a great extension tool. It's a great way for me to figure out who there's a gap in knowledge, and that I need to do research on. So it's helped in many ways. We have a number of farm advisors that also develop the interests of crop manage in different parts of the state. And so it's sort of the idea is spreading, I guess, you see.


Craig Macmillan  17:44 

Yeah, exactly. I hope that it doesn't happen spreads amongst growers. What is the one thing that you would tell growers on this topic, broad topic?


Michael Cahn  17:54 

Well, this broad topic of water management of vineyards, there's a lot of different opinions. What I see, at least in the Salinas Valley, is growers, you know, they they stress those vines a lot, a lot more than they realize a lot of their decisions come from watching the vines and how the tendrils are, you know, how they're growing. And they don't want too much canopy, so a pullback on the water. But it could be that at some point, sir overstressing the crop. And so having good sense of how much water stress that crop is experienced would be something I would like to investigate more.


Craig Macmillan  18:36 

Especially if you're going into a hot spell. You know, I mean, it's one thing you Oh, hey, these vines, we want to keep the very small, we want to have stress in this. And then suddenly, next thing, you know, it's 10 days of 105. And it would have been nice for that plant to be in a little better shape going into that. But how do you know, right? That's philosophy versus prediction versus technology. But this is a great tool to help you with that.


Michael Cahn  18:57 

Right. And so one feature I better talk about in the development for vineyards is you can decide what percentage of potentially ET you want to apply to your crop for each irrigation. And if you enter the amount of water you applied, or the hours you applied, we have another part of crop manage called the saltwater balance. And it will actually calculate how the soil profile will look you know, in terms of depletion of moisture, and we've calibrated that pretty well by using soil moisture sensors. For example, one vineyard we did last year, outfitted with soil moisture sensors and in ran this and it was pretty obvious from the soil moisture sensors, you know, they really depleted the lower part of the profile, you know, by July and it just never went up even with each irrigation they waited up the top foot but you know there was as much moisture down deeper. And so, you know, the soil water balance showed something very similar. We showed this data the grower, and they said, That is not what we wanted to do. We want to keep some of that deep soil moisture. You could use this as a tool to help you understand just how much you are stressing the crop.


Craig Macmillan  20:21 

Where can people find out more about you and CropManage in general?


Michael Cahn  20:24 

Well, we have on our website, help link, which has tutorials as introduction to CropManage, we do crop manage workshops. Usually during the winter time, where it's hands on, you bring a computer, or cell phone or whatever you want to interface with CropManage. And by the way, you don't need a computer a desktop computer, or laptop computer to use CropManage, it works just fine in tablet. And it's definitely meant to be used with a smartphone out there in the field. Because the interface reconfigures for the different screen sites. It is used in a web browser environment to be recommended using Google Chrome or Safari attending our workshop. And we also say, you know, call it the crop manage hotline, which is my office, and I'll leave us with some contact information.


Craig Macmillan  21:24  

Perfect, but we're about out of time. I want to thank you Michael. Like I said, this has been a long, long road to get to this point. And I'm very happy to see the progress that's been made. And I'm happy to see that it's still going. This kind of work needs to be funded. And I know that you relied partly upon donations, and I hope that our listeners will put a couple of bucks in the hat somewhere to keep this going. We appreciate it. But it's a fantastic idea and a fantastic amount of privacy all made. Our guest today is Michael Cahn. He was former adviser for irrigation water resources UC Cooperative Extension Monterey County and other counties. Thanks for being on the podcast.


Michael Cahn  22:01 

Thank you for having me.


Nearly Perfect Transcription by