Tunnel trouble: increasing many things, but not yield

Show Notes

High tunnel crops often look great for the first few years, but as tunnel soils begin to build up salts and alkalinity, we begin to see plant health problems around years 3-5. In this episode, Natalie Hoidal interviews Dr. Elsa Sanchez and Thomas Ford from Penn State about trends they've seen in high tunnel soils, and strategies for dealing with common problems. 

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The Vegetable Beet
Episode title: Tunnel trouble: increasing many things, but not yield

Ben (00:14):
Welcome to the Vegetable Beet. My name is Ben Phillips and I work with Michigan State University Extension.
Natalie (00:20):
And my name is Natalie Hoidal. I work with the University of Minnesota Extension.
Ben (00:24):
We've been doing this podcast over the last few years, and we're changing the format a little bit for this season. We're going to do some pre-recorded interviews in a three act style where Natalie and I will introduce an episode by talking about why we decided to do it. It might not be us doing it, but we will introduce it. Then we'll have the second part, which is the actual interview performed by us or other people. And then the third part will be a wrap up. What did we learn? Where can we go from there? How are we doing this, Natalie?
Natalie (00:52):
So this podcast is brought to you by the Great Lakes, Vegetable Producers Network. It was kick started by the North Central Integrated Pest Management Center. And our license for Transistor is held by the University of Minnesota Extension.
Ben (01:04):
And you can listen to this episode and all the rest at glveg.net/listen. Enjoy the show.
Natalie (01:11):
Hi Ben.
Ben (01:19):
Hey Natalie. I heard you got some good interviews under your belt here.
Natalie (01:23):
Yeah, so I opened on this total rabbit hole. I think I have known for a long time just anecdotally that our soils and high tunnels are kind of funky. I know there's been some work done on the east coast, but I think for the first time this summer, I started to really see some high tunnels with problems. And so we talked about this in your episode where like things look really good for a few years, around year three, there's this shift. And then at some point, things can start to look really bad. And this summer, for the first time with growers that I worked with, I was seeing high tunnels where the plants just looked terrible.
Natalie (02:06):
There were nutrient deficient, but when we did soil tests, there were tons of nutrients in the soil. And so I wanted to learn more about what was happening and how we can do a better job of avoiding that situation or going back from that situation once we get there. So I reached out to some folks in Pennsylvania, Elsa Sanchez and Thomas Ford who have been doing this work, seeing kind of the same things to try to get a better sense of what they've been seeing, how they've been remedying situations like this.
Ben (02:41):
Yeah. I really enjoyed this interview. They were a real funny team.
Natalie (02:45):
Mm-hmm (affirmative).
Ben (02:45):
You can tell they worked together for a long time and.
Natalie (02:48):
Yeah.
Ben (02:49):
I don't think that they've trademarked this, but I think they should, because they talked about doing high tunnel 911.
Natalie (02:55):
Yeah.
Ben (02:56):
Or the other term they used was tunnel trouble.
Natalie (03:00):
Yep.
Ben (03:00):
Tunnel trouble. I just love that. Tunnel trouble 911.
Natalie (03:02):
Seems like it should be a talk show, right?
Ben (03:04):
Yeah. It really should be.
Natalie (03:06):
Like car talk? But for high tunnels.
Ben (03:07):
They'd be good at it.
Natalie (03:10):
Yeah. So they kind of walked us through the same things that we're seeing basically like people adding a lot of inputs to high tunnels. I think we tend to treat high tunnels differently. They're like this really high value space and we want to get as much as we can out of them. And so sometimes we, just the psychology of how much compost you're adding. And you're not thinking as much about economics when it's on a per square foot basis versus a per acre basis. And so you'll hear in the interview just talking about how salts can build up alkalinity can build up and the PH can change and they share some really good tips for dealing with that situation and also for preventing it. And it seems like avoiding that situation is easier than coming back from it. So people who are building new high tunnels, hopefully have a lot to learn from what they have learned.
Elsa (04:18):
I'm Elsa Sanchez. I'm a professor at Penn State University. I work with Vegetable Systems and I've been there since 2002, which sounds like a long time but wait till you hear how long Tom's been at Penn state.
Tom (04:34):
Okay. My name's Tom Ford. I'm a Commercial Horticulture Educator. I am based in Cambria county and I cover pretty much all horticultural crops, vegetables, tree fruit, small fruit, greenhouse nursery, and so forth. I have got 26 years in a Penn State, but I actually have 39 years in extension. I also have worked with University of Maryland Extension and with NC State. So I've worked with again kind of a variety of crops and cropping systems in a variety of soils across multiple states.
Natalie (05:09):
Right. Excellent. That's great to have you both here. So in 2017 you worked with 27 farmers looking specifically at high tunnels, but then you also had this data set of over 1300 farms in Pennsylvania and you were looking at phosphorus loading on vegetable farms. So I'm curious, what made you want to do this project? Were you seeing high levels and wanted a better sense or how did you determine that this was something you wanted to look into?
Elsa (05:42):
So I had been working on a farm, I had this three year project with this farm here in Central Pennsylvania. And we were actually looking at bio controls in these organic high tunnels. And since I was going to the farm weekly, the farmer stopped me and she said, some things are going on in this tunnel. I'm not sure what it is. Do you think you can help me try to sort it out? So we went and the plants weren't growing that well, she wasn't getting good yield from, it was mostly cucumbers, but she had said in the past she didn't get good yields either. So we did a soil test and we found out that she had high soluble salts, high PK, calcium, magnesium, and also high organic matter content. And not that long after that, I got called to another farm where they were having a problem with their high tunnel where they weren't growing anything in.
Elsa (06:38):
And I called Tom and I said Tom, do you want to come out here? And let's see if we can figure this out. So Tom and I went and we found a very similar issue where the soils were, same thing had high salts, had high PK, calcium, magnesium, and the farmer had actually stopped growing in the ground in that tunnel. They're using it as a propagation tunnel at the time. Weren't they Tom when we went out there? Yeah. So we thought this problem, maybe more widespread. Because we, in a very short period of time, we worked with two different farmers that had the same issue.
Elsa (07:15):
And so we submitted a proposal to the Pennsylvania Vegetable Growers Association, and received some funding where we could look at both the soils and also the irrigation water from high tunnel farms across Pennsylvania. And so we, let's see, we contacted all the farmers we could think of. And then we also put a notice in our statewide newsletter. And then whenever we'd go give talks, we'd mention that we had this project. And at the end we were able to get 27 farmers to send in both their soil and irrigation water that we then had analyzed at Penn State's Agricultural Analytical Services Laboratory, so that we could see some chemical measures of the quality of both of those.
Natalie (08:05):
That's great. And did you find that those initial case studies were pretty consistent? Were you seeing those same things that most of the farms that you looked at or was there quite a bit of variation.
Tom (08:22):
There really wasn't a lot of variation and it's something that continues today. Anytime a high tunnel soil test comes in. We called our program like a high tunnel 911 rescue, and that's what it's become. Anybody that has tunnel trouble typically reaches out to us. And basically we sort of coach them a little bit. First thing is we asked them to do a complete soil test, including organic matter if they were not selecting organic matter. And the other is soluble salts and we pretty much can... It doesn't matter if they're a conventional producer that uses chemistries and chemical fertilizers, or if they're an organic producer, the numbers are very similar across the board. And so what we just have to do is we have to figure out kind, what is the best mitigation strategy working one on one with that grower.
Tom (09:21):
And then even though our focus has been on some of the nutrient pieces, one of the things that we often require is that they do a leach of the soil. And when we ask them to do a leach of the soil, we also need to know what the water quality is. And even though growers routinely do soil testing, they very rarely have done any type of analysis on their irrigation water supply. And so we were finding water sources that growers were using that had elevated soluble salts as well, very high alkalinity. And then we found even, I think one or two that had high arsenic levels above EPA drinking water limits, which threw us a complete curve. So we worked for a lot of these growers too in looking at some form of acid injection. Be if they were organic, we looked at Citric acid. If they were conventional producer, didn't mind using sulfuric acid, we worked with them with sulfuric acid, but we tried to basically provide some level of a mitigation strategy to those growers to make those tunnels work again.
Natalie (10:29):
Yeah. So that's definitely something we're seeing as well. People are kind of just starting to test their water and realizing that a lot of water really needs to be adapted or treated. So I want to back up a little bit. So I think something that we always talk about with high tunnels is you don't have that rainwater to flush out the soluble salts that are building up. And so people know that going into it, but I think from your data and also from what we're seeing, it's not just the soluble salts, right? We're seeing really elevated nutrients, especially phosphorus. And so I'm just curious to get your take. Do you think it's just a function of salts building up due to a lack of rainwater or are people really treating soils differently? Are you seeing really heavy compost applications in tunnels that you're not seeing in fields or yeah. Just what are your thoughts on that?
Elsa (11:33):
It seems that high tunnels they're just very different than managing crops in the field. They tend to be a little bit less forgiving. And most of the time when we were seeing these high levels, as Tom said, it didn't matter if it was an organic farmer relying on organic nutrient sources or a conventional using inorganic nutrient sources. We're seeing this build up of the fertilizer salts over time so that was the main issue that we were seeing.
Natalie (12:10):
And in terms of the levels that you were seeing, you were at pretty high levels of everything. For this particular episode, I'm interested in phosphorus and kind of understanding the broader impacts of that. So can you just talk about like how high were those phosphorus levels and is that something you're concerned about from an environmental perspective or just kind of a crop health perspective? What are you doing with that information going forward?
Elsa (12:44):
So they did reach levels that we were concerned both from the plant perspective, again from an environmental perspective. And along with the soil and irrigation water quality or water samples that these farmers sent in, we also had them fill out a short survey and one of the survey questions was, were they satisfied with how their plants were growing in the high tunnel. And most of the time the answer was no. And so it was related, I think, to the excess nutrients and the high salts, for sure. And so, yes, it was something that we were very concerned about and it was something that the farmers were largely unaware of too before we did these testing and we followed up with all of them with letters.
Elsa (13:25):
And as Tom mentioned with the salts, a lot of them were also getting them that way. We're offering... We don't have a ton of solutions for high phosphorus, right? It's not the same. But one thing is using cover crops and growing them in the tunnel. And then the key would be then to take the cover crop out of the tunnel instead of turning it back in, so that you're removing the nutrients. And Tom, there was one farmer where we bought some cover crops for them to do just that I forgot what they were. It was like, what was it? Beets, sugar beets and wire or something.
Tom (14:00):
Right. We were trying to work with a grower sugar beets to help both mitigate some of the salt levels and hopefully take up some nutrients, be able to move it around and then use the beets then as a harvestable portion that they could come back in and then feed some of their livestock with. It was just more, again, anecdotal at this point in time. But we also have another sort of side project we're working on right now. We're actually trying to look at some of the crops that you've been able to grow, to try to mitigate some of the salt issues. That'll hopefully take up some of that excess fertility as well. But when you think about the producers that we work with, and there's a lot of, again, I hate to point the finger at really some of the causes, but we have a lot of growers that just don't have the experience level.
Tom (14:54):
There are growers that don't understand basic soil test, who don't know how to read a soil test. We have consultants that are pushing fertilizer and putting profits over environmental stewardship. And I hate to say that because I know I'm going to be stoned the next meeting I'm at, but we've seen consultants over recommend product. They're extremely above optimum, excessive applications of phosphorus. But you have an operation or a consultant telling growers, well, you need to throw 9, 15, 30 at it. And we know we're flat lined over potash. We're flat lined on phosphorus.
Tom (15:37):
And so they're selling product in most cases, instead of trying to fix the problem. And to me that's a bigger issue on the organic side, we've conditioned organic growers to routinely think about compost to manure, and they are completely missing the fact that they're loading more and more phosphorus with that compost and such. So we've got to change that mindset and we don't have, in Pennsylvania, we do not have any type of mandatory nutrient management plans for high tunnels, vegetable operations, or anything. Some states do, especially on the Chesapeake Bay RIM. The other thing that we look at is that because we don't have those nutrient management plans and any type of certifications, then operators can continually put whatever they want down under those crops, those tunnels, whatever. And that just, again, I think creates a bigger issue for us down the road.
Elsa (16:40):
Another thing I think is that high tunnels are still relatively new and their management of them, the soils and all that, is just so different than outside, or even in a greenhouse. I've had a farmer tell me I've been growing in high tunnels for a decade now, and I still don't feel like I quite get it all. It's just completely different than other systems. And it's not quite as forgiving as the field. We've seen issues with access, nutrients and high salts with a single application of compost. So it's just a different system.
Natalie (17:17):
Yeah. That's all really good insight. And I think to the point about, we have mostly organic growers in Minnesota, folks using organic practices. And there's this idea that like more organic matter is always better and that's a resilient strategy. And that's to some extent from consultants, but I think also universities and extension have sort of accidentally promoted that message, maybe not even accidentally, but now we're kind of seeing the other side of it.
Elsa (17:46):
We had an expert, well, it was kind of a study years ago where we were partnering with farmers and asking them, how do you apply the compost to your fields, this is for outdoors. And the number one answer was we're applying just based on what we have on a hand. And that strategy will get you in trouble in a high tunnel, whereas in the field, you'll probably be okay for a little while.
Natalie (18:09):
So I'm curious to talk about some of the solutions you mentioned. So we talked about using a cover crop and actually harvesting that cover crop to get some of those nutrients out. You also talked about flooding high tunnels. I feel like that's something that we talk about, but we don't give a lot of specific guidance with. So I'm curious if you can give some insight about how that works, like how you're treating water before you do that. If you're acidifying your water to a certain point before you do that, flushing out process, how much water is needed, how often you're doing it.
Tom (18:53):
Well, unless they have a water quality issue, and we have to stress to the growers that the water has to be of an acceptable quality. If it already has high elevated salt levels, and we do have some water sources, unfortunately, where we're dealing with 300 parts per million sodium, 250 parts being chloride. We can't tell them to leach their soils or something like that. We may actually encourage them to bring water from off the farm or bring surface water in, or potentially even use rain water to try to do a leach. As far as amounts go, and again Elsa can elaborate, but we've been using some data out of California. And our basic go to recommendation has been about six inches of water to reduce the salt levels by about 50%. Now that's the book value we've used, but we can tell you that we've had some growers.
Tom (19:47):
We had one grower based on his soluble salt levels from his test. And what we required technically 14 hours of leaching, excuse me, 14 inches of water to do basically leach the salt, 14 inches of water. Well, he did his 14 inches of water, very diligently. And then he let it dry a little bit, came back in, took another soil test and we still had to do another leach. We weren't able to get his salt levels down to actually, he had put down 31 inches of water in a 2,800 square foot tunnel. So can take copious amounts of water, and then you have to wait for the place to dry out again, before you can come back in and plant.
Tom (20:32):
So that's the one strategy that's been the go-to, if they can't move their tunnel. We have Mennonite growers in the Northeastern part of the state from a cultural standpoint, they always take the plastic off their tunnels every winter. And we don't see the salt issues in their tunnel. We don't see as much accumulation and nutrients in their tunnel. And then the third one is I have got Amish growers that routinely move their tunnels every year. And that's again, another mitigation strategy. So different approaches for different growers and different growing operations.
Elsa (21:13):
I was managing four organic high tunnels and we applied... Well, what happened was that the skin of the tunnel just ran out of its life and it ripped over the winter. And instead of replacing it right away, we left it off until the following spring. And we recorded how much rain that we got and the salt level decreased in accordance to that recommendation that Tom was giving. So at six inches of water to each out about 50% of salts in the top foot of the soil that comes out of California again. And then the other thing I wanted to mention is about the water too. A lot of high tunnels are equipped with drip irrigation systems. And so if you are using water, you really have to think about how you're going to get the water throughout the whole tunnel. So if you can bring a sprinkler in irrigation in for that, for example, that would help a lot.
Natalie (22:02):
Yeah, that's a great point. All right. One other thing I wanted to ask, you know you two are really focused on high tunnels. But in the publication I read, you were also reporting some of those numbers from vegetable fields where you were also seeing really elevated phosphorus levels. And I was just curious about that. It looked like maybe you got that from your state soil test database or something. Were you seeing big differences between vegetable fields and other types of crop fields, or does Pennsylvania just have naturally high phosphorous levels in the soil? What was going on there?
Tom (22:44):
We are a livestock intensive state and most folks basically balance their nitrogen needs with manure applications. And don't look the phosphorus. So the tendency, like in a lot of areas, the closer you are to the Barnyard, the more manure that gets supplied. And so many growers have aren't even thinking about phosphorus and phosphorus indexing on their soils. So we have a tendency to see very elevated phosphorus throughout. And then we think about vegetable growers. A lot of our vegetable growers are smaller plain sect operations, and they tend to be a little on the thrifty side. And so manure to them is a free nutrient source. So the tendency is they haul manure as the preferred nutrient source in their fields, even though they started to grow more and more cover crops, they still typically were greater practitioners of the art of using manure.
Natalie (23:46):
Yeah, I think that is pretty consistent across the Midwest. We have a lot of animal processing and production as well. So even for folks who aren't raising livestock, that tends to be some of the most affordable fertilizer you can get, so that's pretty consistent, I think, with what we're seeing. Is there anything else? I think that was all the questions that I had sent ahead of time, plus a few extra curve balls. Is there anything else you want to add?
Tom (24:18):
Well, the only thing is we tried to stress, Elsa and I were part of a program I guess, about a week ago or so maybe two weeks now, but where we try to stress some nutrient budgeting aspects. And what we find is that growers, for the most part, they get their soil test done. They read the recommendations, but they're not factoring in cover crops, they're not factoring the manure. And so if someone tells them to apply X number of pounds of purchase fertilizer, they're doing that. And they're not looking at anything with crop history or anything else to reduce those nutrient needs. And so that's always problematic. So we were trying to stress from an educational standpoint, the need to do more nutrient budgeting before they actually buy that first fertilizer in the spring or make that first application of manure.
Natalie (25:10):
Yeah, that's a great point. And when you're talking about budgeting, you're talking cover crops, you're talking nutrient credits from previous manure applications. Is there anything else people should be thinking about in that process?
Tom (25:24):
Even the organic matter piece. Elsa probably could elaborate, but we've had soils in high tunnels. I hate to go back to the high tunnel route, but she had some soils in high tunnels where the organic matter level was the point where the soil looked like it was a soil less pit like mix. And so they're not even factoring the decomposition, the organic matter, and the re-release of the nitrogen for the new organic matter. So in some cases, if you look at the organic matter level and then also factor the nutrient release, there may be plenty of nitrogen just coming from the breakdown of the organic matter. And that's something that almost everybody discounts.
Elsa (26:09):
Yeah. We definitely had some tunnels where it was like 15 and a half to 19 or sorry, 16 point something percent organic matter where the lab even called me back and said, we check this twice because we haven't seen them this high. And we were seeing that high coming out of high tunnels. And Tom's absolutely right. That can be looked at as a contributor, excuse me, to your nitrogen. There's some credit there.
Natalie (26:37):
Yeah. This has been really helpful. Thank you so much. I appreciate your time.
Elsa (26:41):
This was really fun. I've never done this before. Tom, it was so fun doing this with you and you and Natalie are great. Thank you.
Natalie (26:51):
You were a natural in your first time.
Ben (27:05):
That was a great interview, Natalie. I enjoyed listening to them. There's something they talked about that I thought I hadn't really thought much about before, but one of the solutions they proposed for having excessive nutrient levels in the hoop house was to plant the cover crop to harvest, to remove from that space because otherwise you get recycled in that same space. And I thought that was a really cool way to think about things. And the example that Tom gave was, I think, sugar beets to be fed to livestock.
Natalie (27:39):
Yeah.
Ben (27:40):
And so I wonder what other opportunities there are for that. And I also wonder if how important it is to pay attention to what happens to the manure, if that's the situation like, are you then composting the manure to then reapply.
Natalie (27:57):
To not bring it back in.
Ben (27:58):
Right.
Natalie (27:59):
Yeah.
Ben (27:59):
You got to be really careful about not bringing it back if you're trying to draw it down.
Natalie (28:04):
Yep.
Ben (28:04):
But I thought that was a neat concept.
Natalie (28:07):
Yeah. And I don't know about you, but like in Minnesota, at least we're seeing a lot more people interested in integrating livestock and vegetables.
Ben (28:16):
Same here.
Natalie (28:16):
It's obviously complicated because of food safety, but.
Ben (28:19):
Yeah.
Natalie (28:19):
By keeping them separate like that. Yeah. That's one way to do that to remove some nutrients from your tunnel while feeding your livestock and then maybe spreading that out elsewhere on the farm.
Ben (28:31):
Mm-hmm (affirmative). And later on in the interview, I believe it was Elsa who got into this. She was talking about how the quality of water is not as tested as the quality of soil in many of these systems. And when it comes to the question of whether just applying water can help leach some of those nutrients out of the root zone, could you be making things worse if you didn't know your water quality.
Natalie (28:57):
Yeah.
Ben (28:57):
I thought that was a good point to consider and in this interview that you hear later.
Natalie (29:03):
Yeah. I was really glad they talked about it. I don't think we talk about that enough. Most growers I know are not testing their water at all and we don't really tell them to. So I was really happy that came up and it's definitely something I'm going to be encouraging more of with growers that I work with.
Ben (29:21):
Yeah. I agree with you there. I also don't tell growers or recommend that they do it very much, but now that I'm thinking about it after hearing this interview in a hoop house where the only water being provided is what.
Natalie (29:34):
Yeah.
Ben (29:35):
You're giving it. I think that it's really, it's deserves a lot more attention than it gets.
Natalie (29:41):
Yeah.
Ben (29:43):
And then the concept of moving the tunnel and removing plastic is one that, we've all heard it said. It's sort of like, how often should you be flossing?
Natalie (29:55):
Yeah.
Ben (29:55):
We've all heard it.
Natalie (29:56):
Yeah.
Ben (29:58):
But I've seen many movable tunnel where the weeds have choked out the rails and they no longer moved because they never got moved.
Natalie (30:05):
Yeah. I have not seen too many movable tunnels. I think most of them are posts are concreted in and so there's not much you can do, but.
Ben (30:13):
Yeah.
Natalie (30:14):
I do think if obviously people aren't going to take off plastic every year, but I think it's very reasonable to recommend in the years where you're changing your plastic anyways that that could be like every four or five years get a lot of snow in there. Try to have the whole winter open so you can get a lot of rain water in, that feels like a good compromise. And especially as people build more tunnels, I think there's, I guess I'm seeing a lot of people get a second or a third tunnel and that allows you that much more flexibility.
Ben (30:46):
Yeah. You can cycle one out for example, and have it top off for a season if you can justify that.
Natalie (30:54):
Yeah. Well, so this interview kind of led me to the second interview.
Ben (31:03):
Yeah, I can see that.
Natalie (31:04):
I was very inspired by like just the issues that I was seeing this summer in tunnels. And then as I started to dig into it and hearing from Elsa and Thomas as well, like really understanding just how much phosphorus we're putting on to vegetable farms and wanting to understand if that's a big deal or not. And whether we should be talking about it. I think some of my initial hesitations were one, at least this is not issue where you're at, I know vegetables are more a part of the landscape in Michigan, but vegetable farms tend to be pretty small in the Midwest.
Natalie (31:38):
Also, they tend to be folks who are really conservation minded who have strips of perennials and buffers. And so, if we have a lot of phosphorous on these landscapes, doesn't really matter aren't there better places to be pointing our fingers. But I do also think that vegetable farmers really care and want to be doing the best that they can be doing for the environment. And so the second interview is an exploration of that. How much phosphorus are we putting out there and how much does it matter.
Ben (32:15):
That concludes this episode of the Vegetable Beet. If you'd like to check out all of our past episodes, head on over to glveg.net/listen. Sweet.
Natalie (32:27):
Okay.
Ben (32:28):
Thanks Natalie.
Natalie (32:29):
Okay. I got to run.
Ben (32:30):
Yep.
Natalie (32:31):
Okay. See you.
Ben (32:31):
All right. Okay. Bye.
Natalie (32:31):
Bye.

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