 Okay everybody, let's wrap up tonight with a talk on sprayable biodegradable mulches. Okay plastic mulches are used to suppress weeds and we've talked about them earlier in the forums but the disposal of these plastic mulches is costly. It's costly to the environment and it's costly to our pocketbooks. So NDSU is working in collaboration with other universities to develop environment friendly sprayable biodegradable mulches. Now I just have to say this presentation is a higher end presentation okay. This is not fluffy stuff here. We're going to learn about some serious research. I think it's very valuable for us avid gardeners to see the type of research that goes on in NDSU and all the work that it entails but we've got to focus in this presentation here okay. Now here to share with us her findings on this topic is Dr. Greta Greenmig. Greta is an associate professor in the department of plant sciences at North Dakota State University. She teaches courses about weed identification as well as weed biology and ecology. Greta's current research interests include non-chemical weed management, integrated weed management, weed ecology, and weed management in organic production systems. So Greta welcome to the forums. Thanks Tom and welcome everyone to this final talk for this evening and as Tom mentioned I'm going to be talking about a research project that I am doing with a lot of different collaborators you'll see here and this is a big grant funded by the main USDA program that funds organic research and our goal is to develop and evaluate biodegradable liquid applied mulches to replace polyethylene film in organic horticultural production and so why would we want to do this? Polyethylene film or plastic mulches are very very widely used in horticultural crop production especially in organic systems where they can't use herbicides and there's many reasons they're inexpensive, they suppress weeds really well, they modify the soil temperature to provide optimal growing conditions for the crop, they retain soil moisture and they are often used to contain soil fumigants as well but there's a number of drawbacks associated with plastic mulches they absorb and concentrate pesticides that are applied they're very difficult to remove they're super fragile and thin, they tear, they break into pieces, they're not readily recyclable and all those plastics whether they're in the soil or in a landfill or in the water require hundreds of years to break down it's becoming an issue in our society that we're becoming more and more concerned about because we really don't know all the health impacts that may result from the ubiquitous exposure to these microplastics and you might be thinking well I know that biodegradable plastic films exist and they do but they're currently not allowed for US certified organic production and that's why we were given this grant to work on trying to develop liquid applied biodegradable cellulosic mulches so we're working with a large team and the team in Montana State was working on developing and testing the physical properties of a bunch of different hydromulch formulations that's what we call this liquid applied mulch it's called the hydromulch and they tested a number of different cellulosic fibers materials that you'll see on the screen and added a lot of plant-based tachyfires gargum, psyllium husk, and camalina meal they added those at two four and six percent by weight dry matter to hemp herds, cellulose paper, thermally treated wood fiber, and then some combinations of these and they tested some physical properties here are the physical properties they tested tensile strength, puncture resistance, rain, fastness, soil adhesion, and density all things that we suspect might be related to the ability of these mulches to resist weeds that's the main function that we're interested in is weed suppression some of the things they found were that the paper really worked best especially with a tachyfire added and gargum was better for strength but the psyllium husk and camalina meal were better in the rain fastness test and they're also thinking that we might look into the hemp a little bit more it didn't perform as well as paper alone but that material is less costly and we found a new source of it that's more finely pulverized that we think might be a promising material but we decided to go ahead with some field trials using the paper-based hydromulches and we conducted these field experiments last summer in Washington and North Dakota and we were testing five different hydromulch formulations these were paper only and then we had two and six percent psyllium husk two and six percent gargum and we compared all five of these treatments to the polyethylene mulch which is the weed free industry standard and so we applied the mulches first at about 4500 kilograms of dry matter per hectare and then we planted our berries strawberries into these mulches and this gives you an idea about what the field sites look like the mulches were applied to standard raised beds that we built with a bed shaper and a tractor and then on the left is the North Dakota side on the right is the Washington site and you can see our application equipment which was tractor mounted and I'll give you a little view about what that was like here's a video of the machine that we developed in North Dakota applying the hydromulch at our site and the Washington machine was similar it performed almost identically to the machine it wasn't identical in components but it was identical in action for the most part we did have some application issues that were hoping to solve we had to apply two or three passes to achieve adequate coverage so we'd like to get that down to one pass and we're looking at some double nozzle configurations to try to achieve that also we realized that applying before planting might always not be ideal and we're working with a farmer who actually is working on a system to transplant first and then apply the mulch on top of the transplants and so we'll see how that goes another thing we notice is that the soil surface roughness affects the coverage and so that's something that we need to understand better and also we notice that sometimes we thought small weed seeds were dispersing via wind onto the top of the mulch and so that could be an issue for people who have lots of bare soil in their system so those are some of the things we're going to work on I thought just for people this isn't really meant to be something that home gardeners could do but I thought I would mention that we did do this project on a smaller scale previously this is one of my graduate students applying the hydromulch slurry using a regular backpack sprayer that we modified a little bit and you could potentially shred some newspaper and mix it in a bucket with an immersion blender as shown here and then apply it this way if you wanted to test it out yourself it's pretty simple just shredded paper mixed with a little bit of gargum would be a good formulation and then in Washington the group there was playing around with not having to shred the paper because we usually were using in our trials we were using shredded papers so they would soak their crumpled newspaper sheets in water for 12 hours and then they would mix it first with a paint mixer to kind of chop it up into tissue size pieces and then they would use the cement mixer in the center to achieve kind of a finer liquid hydromulch preparation so those are just a few ideas if you think you'd like to give this a try I don't really recommend it but some people are interested in that so I thought I would throw that out there so this is a picture of what the hydromulch at Absoraka in North Dakota looked like with the six percent gargum and you can see that it formed a pretty nice surface it repelled the weeds really well and the strawberries grew really um excellently with it I thought I'd show you a few of the results and hopefully these graphs don't throw you off they're really easy to read on the horizontal axis which is the x-axis that's showing the weed density so the longer the bar is the more weeds there were the um placent mulch had zero weeds so that treatment isn't included we're just comparing the hydromulches and we measured the weeds at two different times peak emergence and then later on in the season and at peak emergence we saw that the gargum formulations suppressed the weeds a lot better than the other ones so we're you know pleased with this result that was a pretty low density of weeds and this was a result that was consistent across our sites then when we get to the later weed density assessment the two sites were a little bit different there was a lot of variability at the top of this figure are the washington results and the little a's mean that all these means were the same statistically I know they don't look the same but if you look at these t-shaped bars those are the errors and that shows the variability so there's so much variability that we couldn't really tell these means apart statistically so it looks like they were different but they weren't but in North Dakota we saw the same pattern we saw earlier which is that the six and two percent gargum formulations suppressed the weeds a lot better than the other hydro mulches so that was weed density we also saw that when we split the weeds into broadleaves and grasses and this was at Washington only that the formulations differed in their ability to suppress grasses and this is interesting because we've noticed that grasses are harder harder to control with the hydro mulches and that's because of their morphology when they emerge they just have a single little coley-optile leaf it's like a little needle and it's really easy for that needle to find any tiny hole or push through that hydro mulch and so we did see that the gargum formulations were better at suppressing those grass weeds which is an important result looking at total weed biomass we see that for the washington site there really wasn't any difference again but at the North Dakota site we did see that the six percent gargum had a little bit less weed biomass associated with it we measured mulch deterioration and we saw that in washington there was really no difference statistically although again it looks like there was between the poly mulch and the hydro mulch formulations but in North Dakota we saw that the poly film was as good as the gargum so again that's another vote for the gargum maybe being a little bit better here's some fruit yield we measured marketable yield in both weedy and non-weedy areas of our plots and at washington even though there were tons of weeds in the hydro mulch we didn't see a difference in yields and this is something that they've seen many times in their trials out there in washington that the weeds don't really seem to impact the strawberry yield all that much and so it's kind of a vote for in some systems in some scenarios maybe weeds aren't always that big of a problem and we can learn to live with a few weeds in North Dakota we had a very interesting result which is that the gargum formulations this hot pink bar and the charters bar labeled with the bees those had higher yield than the poly film and also the paper only and that was very surprising to us we noticed that the strawberries flowered later in the poly film and we think it is a temperature effect in North Dakota we have very hot summers compared to washington and i think that black plastic mulch was just too hot for the strawberry plants whereas the hydro mulch was more of a light color um this was also in uh marketable yield in a weed free area so this is showing the effect of just the mulches without the weeds and we see similar patterns as in the weedy areas there were no differences among the mulches in washington and then in north dakota we see that the gargum formulations performed a little bit better than the other mulches to conclude we will be continuing with this project until 2025 and in the coming years we're going to be evaluating these hydro mulches in blueberries in washington and then in north dakota we'll be looking at their performance in an annual vegetable production system and the coming experiments will contain a lot more information about the soil impacts that would result from incorporating all of this cellulosic material into the soil and we're also going to continue to refine our formulations and improve our application methods and the study also will include some comprehensive economic analyses to compare costs but our goal at the end again is hopefully to come up with at least a step forward in terms of developing a commercially viable biodegradable mulch that could be applied to raised beds via spraying and again this was a collaboration between montana state university washington state university north dakota state university and the usda ars so lots of different groups and lots of different people and with that i will take any questions if you have them okay thanks credo uh can you see what the heck is guar gum and is it expensive and where can you buy it what's it come from um it comes from a plant and it's just a plant-based gum and you can buy it we got ours at an herbal supply store it's a very common food additive it's it like if you buy coconut milk in a can look at the label it will almost always contain gargum so it's an edible gum that's in a lot of foods and we got ours from this herbal supply company in oregon called mountain rose herbs but i bet you could just get it on amazon it's a pretty common material and then the psyllium husk is also from a plant a plant seed and that's the same stuff that's in the it's like a dietary aid called metamucil you might be familiar with that so it's the same stuff and the camalina meal which we didn't use in our field trials but we're still working with it in the lab and in controlled environments that is a byproduct from growing an oil seed called camalina it's a brassica it's related to field pennycress and maybe canola and the seeds are pressed for oil and then the solids are left over and so the camalina meal are the solids left over from that so that's a great question how about like when you uh what when you're like putting in the transplants so you spray over the bed first right and then you plant immediately or how fast is that hydro or that uh i want to call it hydro mulch how fast is that hardened off oh that's a really great question so and and luckily the picture you're looking at shows this this is what it looked like right after we planted it so we'd spray on two coats and after the second coat the hydro mulch would still be relatively flexible and we used kind of just a flat metal bar to push the roots of the bare root strawberries into the soil but we had some other studies that i didn't talk about today where we were looking at cabbage as well and for that we waited until the hydro mulch was more hard and we used a hole cutter to punch a hole in it and so you could do it either way and we just use a little hand trowel and planted the plants by hand i think that for some crops it would work better to plant the crop first and then apply the hydro mulch on top and a farmer that we're working with up near Grandin has a system that he hasn't gotten it to work quite all the way but he did have a system that was applying the mulch to a transplanted row of kohlrabi we did this last spring and the four i thought the force of the application would break those plants but it didn't they were really resilient he just didn't have the right nozzle size and he didn't have a powerful enough pump on his tractor to drive the the pump to mix the hydro mulch to be smooth enough so it kept clogging the nozzles so there's a lot of technical details that have to be worked out of the process but if you sprayed directly on top of the kohlrabi or whatever do you have to wash off right away with these plate water on top of it to wash off the hydro mulch off the plant no it didn't really seem to coat it the way we had the nozzles aimed it didn't it didn't uh it was aimed so that it didn't really cover the top of the plant just scoot it along the side of it was kind of angled and it and it formed kind of a fan shape uh pattern just below the leaves of the kohlrabi so they they grew just fine according to the farmer i talked to him about that last week but we just couldn't we didn't get a high enough rate on to suppress the weeds because of some problems with his equipment that he's working on and and so when you do that hardening process how soon do you follow up with the planting itself before the material hardens or how how fast does it take for that that mulch to harden it depends on the weather but if it's relatively dry and sunny it will harden in about 24 hours but you can plant whether it's if it's hard you need to have some way to punch a hole in it and so we were using a drill with a hole cutter on it that you could just punch a hole nice and clean you know because if you just try to stick a a shovel or a little trowel into it it'll crack and split so you need to sort of punch a clean hole and then plant into it i think that's not gonna be that would not be a viable method on a large scale but strawberries are planted into plastic mulch and we were copying a pretty standard planting approach for strawberries and so i think the strawberries would be planted into the mulch after it's sprayed but for other crops i think it would probably be better to transplant the seedlings and then spray it on okay so how about the how long does this mulch last like how fast is it degrade is there any could you could it be there for two years i don't think so i think you'll still and we'll find that out because we haven't done that yet but in the spring if the snow ever melts we will go out to absuraka and see what's left and i have a feeling we'll still be able to see some of it but you i don't think it will be intact enough to use again you'd have to apply it every year how about a what what specifically is there about that guar gum why did you choose guar gum is that for it's tachyfine or like what is that it's sticky and it i see it helps the paper fibers it's like a glue you can think of it just we call them tachyfires that's the technical name for it but it's really just like a glue that helps to glue the paper fibers together to give them a little bit more cohesion and strength okay does the this hydro mulch does it affect the ph of the soil or the soil microbes well that's what we're going to find out because this first project was just a one-year project we needed to do to see if we could even get this stuff to work at all like it was a lot to figure out how to apply this stuff and how to make it but so we only looked at weed suppression and crop performance last year but in the coming years we will be doing very comprehensive soil health measurements to quantify those impacts if i had to guess i think that we will certainly see some impacts of incorporating a high carbon material into the soil how much i don't know it's not a huge amount it's probably not even as much carbon as a typical crop residue and so it may not be a very great impact but i have a feeling that you will see some shift in microbial activities and we will see some shift in nitrogen cycle dynamics ph it might lower the ph a little bit if i had to guess because adding more organic matter will acidify the soil to some extent so those are some of my predictions but we don't know yeah so like this spring when the snow melts and you get out there and you look at it what will you do with it if the mulch isn't there enough to do the job do you just are you just going to till it into the the soil there and replant is that what you do with that well we're done with the study so i mean in an annual in an annual system you you know they would apply new plastic mulch every year you know they would reform their beds and put in fertilizer and then apply the mulch and this is no different so it's not a permanent thing it would be an annual application just like the plastic mulches and people are asking about the strength of the mulch as far as will the strawberry runners penetrated or will the squash or pumpkin runners on the vines will they penetrate this mulch um squash doesn't make rooted runners does it no i don't think that so this particular strawberry variety is a day-neutral strawberry and we remove the runners so it's not like a matted row system where you would be looking for runners to proliferate and root in day-neutral strawberries are just grown as annuals and so we didn't we actually removed all the runners but i don't i don't know they might they they probably could find their roots in the soil a little bit better than with plastic yeah but you know in a strawberry we're we are trying to match a strawberry plastic culture system not a matted row system which is something that people are probably a little bit more familiar with here growing june-bearing strawberries in a matted row system and that's not what we're trying to do is this system somewhat comparable to just uh gardeners who lay newspaper on top of their beds and yeah i mean it's the same idea of using a paper-based product the thing about newspaper is it's hard to anchor down and the and you know there are commercial paper sheet mulches it's a product called weed guard plus and we're using that as a comparative treatment in a different study with a different grant that i'm doing and because it doesn't conform to the soil it's very rigid it tends to get torn up and broken up by the wind it doesn't weather very well and one of the nice things about the hydro mulches it's applied as a liquid so it conforms to all the micro topography of the soil it's very stable it's not going to be blown off by the wind didn't you have a problem with it being clogging the your sprayer because of the the viscosity of this type of mulch that you're using uh no we weren't using the typical sprayer that one would use for say an herbicide application these machines it's basically a large tank and we use a really powerful motor from a commercial hydro seeding machine to mix the slurry so it's really smooth and then we have a lower powered gasoline powered pump that we use to apply it because we don't want to apply it with a huge amount of force and but it's enough force that it doesn't clog the nozzle it's a one inch brass nozzle so it's a pretty large nozzle it's not like a tiny nozzle that you would use for herbicides right how about you know could you envision this uh being used for shelter belts with trees you know people use landscape fabric for get their trees going there tons of maybe just to get them going sure yeah i mean it's only one year it's only the last one year the the washington group is doing all their trials in blueberry and that's a really similar type of idea i mean they're you know and they're perennial trees or shrubs and with this type of hydro mulch you're using water can infiltrate the soil is that right yeah yeah how is this comparable to like when you look at along the highways and such when people use this green hydro seeding for lawns right yeah um it's it's it's very comparable it was the whole idea was really inspired by that what we're trying to do is just adapt uh hydro seeding which is like you're saying you it's a commercial preparation that mixes grass seed with shredded paper cellulose and you mix it with water and spray it when there's you know you've got a big disturbance from some kind of construction project they use it to stabilize those disturbances and that's what we were initially inspired by but they're that equipment and the and the formulations that are available none of them are able to be used in organic certified organic production because they use proprietary ingredients that we couldn't even find out what they are and the application equipment is meant to spray this stuff say 30 feet or 50 feet out it's really forceful and so we're trying to develop application methods that are suitable for horticultural systems and it's very different now you know you had a different or different results as far as the weed presence or impacts in washington and north dakota and this person is wondering if the fact that washington as much has more rain that is that one reason why maybe the weeds and has as much impact we're in north dakota we're not really sure and that's one reason why um and i didn't mention this when i was speaking earlier but on this slide you see i've got wet versus dry hydromulch performance and that's something that we're looking to test in a lab to look at the impact of the wet versus dry but i it could be other things too so one issue is just the sheer weed seed bank density right and the site that we used had been in perennial alfalfa out at absuraka for about five or six years and there just weren't the main weed that was out there was common purslane and if you know anything about and some common lamb's quarters those are two very very small seeded annuals and those are the easiest ones to suppress with the hydromulch and as i was mentioning earlier the grasses are the hardest and they had more grasses in washington and another issue the thing about the seeds blowing from bare soil onto the top of it that was happening in washington and they thought that a lot of the weeds were not coming through the mulch but were rather blowing in from bare soil so hopefully you would not be having usually we don't want to have a lot of bare soil everywhere you know so hopefully and hopefully you wouldn't have that but it could also have something to do with the wet versus dry but the other thing is these trials were all irrigated and so it wasn't like they were just dry all the time they did get water pretty regularly and so if i had to guess it's probably all of those things put together here's a question what type of millage is required to block weeds does that make sense to you what type of millage uh they talking about thickness of the material we were we were using one we were using one mil thick plastic mulch it's extremely thin it's just tissue thin and that blocks the weeds we had a hundred percent weed suppression at both sides from that very very thin it's so so fragile and easy to puncture but it you know it will suppress all of the weeds so it doesn't take much but it's different with a material that's organic so for instance if you're trying to use cover crop residue you know you need quite a bit maybe somewhere around 5 000 tons per hectare of dry matter to adequately suppress weeds so it depends on the the material how thick it needs to be or how dense it needs to be how about just wrapping up what's your gut feeling about where this is going like are we gonna in 10 years from now are we gonna be spraying our raised beds with uh biodegradable sprayable mulches i really don't know it could take longer than that certainly this is not a project that's gonna lead to a commercial commercially viable solution at the end of this project it would take numerous iterations to fully develop the idea and there are other groups that are also working on this so it's it's an idea that has a lot of traction because of the extreme concern about the plastics in our environment and i think that the main thing that would help it go forward is if we eventually had some kind of restrictions on the use of plastics and then that would drive it forward i don't know about the economic costs i suspect it would be somewhat more costly but one of our goals was to use waste streams and so for instance the washington group they're actually using a slurry that they get from a facility in washington that's recycling old apple boxes and so a lot of these materials are free or almost free and so hopefully that would help with the cost but i think that the main thing that would drive it forward is to have plastic mulch become less acceptable overall i don't sometimes i wonder if people realize you know they're buying these vegetables at the store and they don't realize the amount of pollution that producing these crops requires and a lot of people will burn that plastic instead of disposing of it because it's so expensive to dispose of and so the environmental impacts of it are considerable that's one of the reasons why i was motivated to engage with the project in the first place okay well we're just going to see where it goes yeah we wish you good luck crater it's high risk you know it definitely is it's it's really interesting and and i think we wish you good luck with it so thank you for the presentation tonight i under i i think it was very understandably did i think it's a great job at downing it down for me so i i was i appreciate that okay okay thank you and now we're gonna wrap it up tonight we're gonna stay on time and we'll just say next week will be our last night of forums and we're gonna learn about trees and how to landscape in small spaces so that's our focus next week we hope y'all have a safe rest of the week and we'll see you next week at the forums thank you good night everybody