“What we’re trying to do is actually incorporate our cover crops into our active growing season.”
— Brian Ward, Clemson University’s Coastal Research & Education Center, Charleston, S.C.
In this episode of the Cover Crop Strategies podcast, brought to you by Montag Manufacturing, Brian Ward of Clemson University's Coastal Research and Education Center in Charleston, S.C., joins us for a discussion about maximizing the benefits of cover crops in vegetable and organic systems. Ward also discusses some of his research on organic watermelon growth and its relation to pollen and bees.
Watch Brian's Presentation from the 2022 National Cover Crop Summit
The Cover Crop Strategies podcast series is brought to you by Montag Manufacturing.
Montag precision metering equipment is helping producers achieve their yield goals while saving on seed and input costs. For establishing cover crops, Montag’s family of seed platform equipment adapts to a variety of major brand delivery systems that will conserve seed and nutrients along with soil and water. Explore new options for your production and conservation goals with your Montag dealer, visit www.Montagmfg.com or call Montag at (712) 517-2775.
Welcome to the Cover Crop Strategies Podcast, brought to you by Montag Manufacturing. I'm Mackane Vogel, assistant editor at Cover Crop Strategies. In today's episode of the podcast, Brian Ward of Clemson University's Coastal Research and Education Center in Charleston, South Carolina joins us for a discussion about maximizing the benefits of cover crops in vegetable and organic systems. Ward also discusses some of the research that he has found on organic watermelon growth and its relation to pollen and bees.Brian Ward:
Today, I want to talk to you today about integrating cover crops in commercial organic and conventional vegetable production. Once again, my name is Brian Ward and I am located at Clemson University's Coastal Research and Education Center in Charleston, South Carolina. And basically, everybody has done a lot of research with cover crops and no-till and when it comes to integrating cover crops into a vegetable production system, we're still kind of new at that and I've got some ideas. Hopefully I can share those with you today and you'll see some... I have some ideas about what you may be able to do with your own farm or talk to other growers about. So why do we cover crop? I mean, basically, to build soil health is a really important factor. Nutrient retention, erosion control, weed reduction.
And so being in the southeast coastal plain, maintaining fertility in sandy soils is extremely difficult. And so therefore, we have to blend of existing cultural practices and like I said, we're actually developing new cultural practices. And so we use cover crops and there is a mixture of plasticulture and also bare ground along with double cropping systems. And we'll talk about that in a little while. So some of the main factors affecting our fertility in our soils is basically the makeup of the soils themselves. Percent sand, the percent loam, and the sand particle size itself. You can travel along the coastline here and have more of a powdery type of sand. And then if you go inland on the coastal plain, you'll have a much, much coarser sand.
So it all depends. There's many factors that... And that affects temperature and microbial activity, all kinds of things. So pH of the soils is very important as well, of course. And for us, it's CEC of the soils, the cation exchange capacity. The organic matter, soil microbial activity, and the growth stage of the vegetable crop itself all take a role into providing and supplying nutrients to your crop and while maintaining your cover cropping system.
So for us, you have, in the upstate, you'll have lots of clay, and we're located down here in the coastal plain. And ours is actually from... Basically, you go from the beach inland and you start seeing this expansion of sand to sand to loamy sand, et cetera, et cetera. So we're over 70% sand in our soils. So if you take the surface area of this clay, take this one little clay particle and stick it inside of this little silt particle, and then you take all these silt particles and put it and place it in this one little sand particle or granule, then you can see that the clay particle has a certain amount of surface area. But if you take all these clay particles and stick it in the silt, you have 10 times more surface area and clay than you do in silt. And then if you do that in the sand, it's like 1,000 times more surface area fold again when you go to sand.
So clay and organic matter tend to have a lot more, cation exchange capacity in your soils. And so essentially, for us in the coastal plain, it's so important to... In trying to build organic soil, organic matter because of the fact that we are so sandy and any organic matter that we are able to generate is quickly and our climate is quickly respired back into the atmosphere. And so we try to actually have longer term cover cropping systems that have actually shown to actually prove a little bit better than doing a cover crop and then disking it and then doing another cover crop. So we're trying to work toward no-till drilling of sequential cover cropping scenarios in order to build our soils.
And so basically, the cation exchange capacity is the fundamental soil property used to predict plant nutrient availability and retention in the soil. It is the potential of available nutrient supply, not a direct measurement of available nutrients. Soil CEC typically increases its clay content and organic matter increase because cation exchange occurs on the surfaces of clay minerals, organic matter, and roots. And so in our environment, you'll note that sandy soils rely heavily on the CEC of organic matter for retention of nutrients in our soils. And basically, you can see we don't test for nitrogen because it's basically, there's no existing nitrogen in the soil, just very little and [inaudible 00:05:41].
But if you note note down here in our organic matter, this is 1.59%. So that is actually one of our medium level fields as far as organic matter. Most of our fields start off in our conventional portion of our farm. We have, typically, our soils are less than 1% organic matter, typically ranging around 0.75%. And then some of our heavier soils started around 3% and we've actually been able to increase those a little bit more disproportionately over the sandy fields. We do have a few fields that have a little bit more loam material in them. And so we've got about 5% organic matter on our most organic fields and we've increased our soil organic matter by about 2% in some fields. But the cat exchange capacity is extremely low, which is correlated directly to the organic matter we have here because there's basically no clay except for our pan layer that we have approximately 18 inches down.
So concepts and terms, and typically, in the past, green manure crops are grown mainly to improve the nutrition as a subsequent main crop and may contain legumes that can add nitrogen to the cropping system. A catch crop is a cover crop that is grown to catch available nitrogen in soil. So if you have a crop of say, let's just use watermelon because I'm going to talk about watermelon later. If you take watermelon and you grow a crop of watermelon, and after the watermelon's done, if you plant a crop of say, cereal rye behind that watermelon, what happens is any nitrogen that's contained in that soil profile that was not directly utilized by the watermelon plant itself will be absorbed into the cereal rye and be made available to the crop that you may plant after that cover crop. So that's just a simple catch and banking type system. So preemptive competition is basically the uptake of soil nitrate by cover crops in the previous scenario so that they won't be lost through leeching or volatilization and be somewhat available to the subsequent crop and also to the soil microbes.
So there's a big thing we'll talk about just in a little bit about carbon and nitrogen and the supply of nitrogen. And so in the past, green manure crops basically were considered to be effective if they were [inaudible 00:08:10] killed or it could be grazed or it could be grazed or killed early in the spring to prevent a preemptive competition so that your green manure crop could be rapidly mineralized. So that was kind of an early thought process and now, we realize that by doing that, we actually lose nitrogen and lose carbon by tillage, especially major tillage.
And so basically, what we're trying to do is actually incorporate our cover crops into our active growing season. High residue cover crops are some of the ones that we can kill without actually destroying or incorporating the carbon into the soil. And so there's a big thing if you're trying to match supply and demand, synchrony between the match of your nitrogen supply from your cover crop and the timing that the subsequent crop is going to need that nitrogen is very, very, very tricky. And then that's where you actually also have to be careful about if you're doing a bare ground situation about side dressing and so on and so forth.
So plowing cover crops into the soil increases soil organic matter to an extent. So tillage loosens and controls weeds and smooths the field, but it also burns up the soil organic matter, CO2 respiration in the soil, and it also speeds up nitrogen mineralization, but it also speeds up denitrification so that nitrogen can actually volatilize as a gas into the atmosphere under certain conditions, and also, so you can actually lose nitrogen through the soil profile and/or into a gas form along with your carbon dioxide in the gas form. So cover crops make no-till more successful. And so what we're also trying to learn how to make no-till vegetables more possible and so no-till with cover crops increase the soil carbon and plasticulture versus bare ground. So we're incorporating it, plasticulture and bare ground.
Some of the crops we've used for cover crops and bare ground scenarios, you'll see at the end, are the cover crops are doing too good of a job actually in controlling weeds. So our selections for zone eight plus and along the coast, it's tropical, directly along the immediate coast. So for winter cover crops, we look at hairy vetch, clovers, cereal ryes, and oat. And for summer cover crops we look at cowpeas, sunn hemp, millet, sunflowers even, some forage turnips are more like in a fall and forage radish is more a fall or spring cover, depends on whether you can fit those in. And they're really good with the turnip crops, the forage radishes as well. For us, I've basically have focused my attention on primarily two crops, that'd be Sudan sorghum or Sudex was on my grass plant. But then I've kind of gotten away from that now, and actually now, I do more sunn hemp more than anything and cowpea.
And so the USDA, about 15 years ago, released improved lines of some sea island cowpeas, 1136, 1137, 1138. And I do have the mineralization rate of the nitrogen residues as they've been incorporated into the soil and I also have the biological profiles of what those cover crops, while incorporated into soils, what different groups of microorganisms they actually stimulate more so to grow. So I do have some data on that that I can share at another time. And the cowpea, so those are really good. And the sunn hemp basically is my go-to now for doing no-till drill. And instead of using the 30 pounds per acre that is suggested, when you do 30 pounds to the acre, you get a lot of much larger stalks and they're very woody, they take a lot of time to break down, but more importantly, they're hard to actually crimp and actually, they're harder to actually create a way of getting a transplant or a direct seeded crop into that soil with such huge... Even with organic matter handlers on your [inaudible 00:12:48] type of air seeders with the material managers on them, it's even harder with that.
So we do 60 pounds to the acre. And 60 pounds to the acre, you only get basically sizes of sunn hemp stalks that are about size of a pencil, and that allows for them to be laid down a lot more cleaner and also allow for a small little spot for a transplant or a seed to emerge from that or be transplanted through that debris and into the soil. And so for winter crops, we've used Austrian winter peas in the past, but I like to focus on primarily one variety. And this year, we actually tried something new and because of supply issues. In the past, I've gone to RegalGraze ladino clover and that clover was designed to be grazed by cattle. And so basically, it takes a beading if it has ample water, it'll actually perennialize to some degree and actually live year round, which makes a great year round type of cover crop system and a semi-permanent double crop vegetable crop system.
So basically, we plant the clover and we only till the section that's going to be used for the plasticulture. And this year, we went to a Seminole ladino clover. And actually, it appears to be actually providing a lot more biomass in the soil and a little bit better cover. And both of these systems work really well and especially in plasticulture systems. All right, so on onward and upward. So more things that we started, we acquired and we learned. So we bought one of these Rodale crimpers and you fill it with water and it adds a bunch of weight to it and it crimps the crop really well. It's a little hard to maneuver sometimes, but the idea is just point it in the direction you want it to go and roll. And so it works really well, it lays it down really well, and there's certain optimal stages of the cover crop that you have to hit when you go to use this or the plant will jump back and regrow. And you don't want that if you're going with a no-till drill.
So this is sunn hemp and so this is one of my go-to crops and you can see how well of a map it creates versus the winter rye. Now, winter rye can do the same thing, cereal rye can do the same thing, but I like this for a fall crop of broccoli. It works extremely well for a fall crop of broccoli. Any weeds that may come up through this are easily early on, easily destroyed in a stale seedbed situation with one of the organic herbicides, acid type herbicides, non-selective, and/or commercial herbicide knockdown in a conventional situation. So now, talking about some of my earliest work with cover crops that has to deal with these cowpeas that we talked about earlier. And the reason why I got out of cowpeas is not that I have gotten out completely, I still use them, but I've found that sunn hemp provides a much longer, has a longer longevity to its above ground biomass for a crop, a fall crop because you're planting a fall crop primarily in August, late August here, which is one of the hottest hours of our year.
Sunn hemp seems to break down a lot slower than does the vines and the foliar matter of these cover crop lines, of these pea lines, these cowpeas, so this is 1136. This is 1137. This is... So one plant covers 100 square feet, so a 10x10 foot section, one seed can completely cover. And these are soft seeded. So these were improved to be soft seeded so they don't regrow and pop up in your vegetable crop two years down the road. And they also have been selected for nematode resistance. So nematode resistance and also, I also have that information on how well they perform under differing moisture levels in the soil. So one of these varieties, I think it's 1136, actually can withstand a little bit more moisture in the soil than the other two. So this is 1137 and these are some early trials we did.
This is 1138. And once again, they all look basically the same, same [inaudible 00:17:30]. But they all act a little bit different in soil. And depending on your soil type and your desires, what you need in your field, you can pick one or two or a combination of three or however you want to look at your field and what you need. So we wanted to look at basically how... And this is some of the data I have if you request it, is how mowing this cover crop and leaving it on the surface versus incorporating it into the soil, what that looks like as far as providing nutrients to the soil and carbon to the soil. And so basically, this is our cover crop planted on those cowpeas, all three different cowpeas planted on a raised bed.
This is a flail mower just to basically mulch and try to get the cowpea completely mulched up. And so it would break down really fast or just stay on the surface as a really good, actually kind of woven mat. And so this is the underside of the flail mower. So this is basically a footprint and a pulverized material. And so it's about three inches thick of matting material and this is when we come back and swept the alleys. And so we did a bare ground check, we did incorporated material, and then we did material just laying on top and then we also did plasticulture incorporation. And so actually, this concept right here with a plasticulture incorporation lends itself well, now looking back on this method, to a method of disease control and insect control, weed control and soils and vegetable protection systems called anaerobic soil disinfestation. So ASD technology. I guess it was basically kind of perfected in California and then Florida and now, Clemson, we're doing a lot of work with that.
And basically, what it does is you take material like this, a carbon source, incorporate it into the soil profile, put plastic over it, flood the bed, make the bed saturated with water, and as the microbes in that soil utilize that carbon, they basically produce CO2 and other gases and eventually go anaerobic. And then there's a series of anaerobic bacteria that'll go in and start producing alcohols and other volatiles. And that kind of sterilizes the soil bed. So there's a bunch of different techniques you can utilize when you're looking at cover crops and implementation into different aspects of vegetable production and different times of that production.
So moving forward, so learning some lessons from the strawberry industry, so in our area, a lot of the you pick strawberry operations and regular commercial strawberry operations, some of our biggest operations are... Typically, our average size is between three and five acres, the strawberries along the coastal plain. And so we actually plant Italian winter rye in the alleys between the strawberry plants so that when rain comes, it doesn't splash disease and sand particles up on top of the developing berries and cause the berries to become diseased with the spores. And that was a technique we used. And we would mow the alleys and so on and it proved to be really effective and I didn't think till later that we could actually start using that as an organic method to keep the field green.
And so that's essentially what we're trying to do, is basically keep the field green. Anywhere there is bare ground, if we keep it green, we're fixing carbon, we're tying up nitrogen, and we're trying to just basically just continual increasing of the soil carbon and we have to do that in order to try to maintain a good productive vegetable system where we're at. Soil's a little bit different on the islands, a little bit darker, a little bit richer, but we're like just on the other side of this tree line back here in the distance, as you can see, actually you can see this is our organic part of the farm. You can actually see a flamethrowing unit back here. It's a four row unit with an orchard flamer modified on the side that we're actually burning some ditches in the off season here.
But beyond this tree line is the intercoastal waterway. And beyond that is Johns Island, which is one of our coastal islands right here in Charleston. So this is basically another year of looking at this is broccoli and this is plasticulture, pre-plant granular organic fertilizer was placed in this field and then we planted the winter rye Italian. And then basically... And this is important because sand does and disease can jump from the soil to up to the tops of when the during from button head formation on. And so this actually eliminates the splashing and also eliminates any kind of sand in your broccoli heads. And that can be the same thing for lettuce or any other kind of [inaudible 00:22:47] crop in the wintertime. It's basically because that's where Italian winter rye grows is during that time period.
And this is just... Basically, this is quality organic produce, just some different lines during the variety trial we're doing that came out of that type of plasticulture system. So now, I wanted to shift gears a little bit and talk about what we've actually done with watermelon. And watermelon is, in South Carolina... I mean, well, technically, nationwide, there's not a lot of organic watermelon. I mean, that's changing every day. But in South Carolina, there was a point where we had actually, we had zero acres of organic watermelon and we still have very little organic watermelon.
Florida's right there with us, they have more. Georgia has more. And so I wanted to try to bring organic watermelon to our state because we can grow it. Our growers are willing to grow it and we have a fair amount of organic growers that want to grow it. And this is just some numbers. Back in 2016, there was 113,000 acres of watermelon, 40 million pounds, and 0.01% of that or 12 acres, were organic production at one point. And that basically was primarily for seed to be sold in catalogs and with some minis in there mixed in in California. So I wanted to explore the feasibility of certified organic watermelon production. And so in order to do that, according to my NOP and my farm plan, I basically had to modify the habitat in which we typically grow watermelons. And that basically meant me incorporating cover crops.
So we set out by modifying watermelon habitat with inclusion of native wildflower species to increase native bees and also clover. And we did this in organic and conventional in 2018. And we also, we collected tissue samples from all plots in the conventional versus organic. We still have yet to run those. We were on the verge of running those prior to the pandemic and now, we're almost about ready to go back into our labs, get our lab running again, and we can run those per carotenoids and phenolic acids inside the organic versus conventional production, and see if there is a difference in the two systems. One is, of course, chemical based, one's organic based, one uses cover crops and pollinating species, and the other one does not.
So moving forward, and for the justification, so this is basically, this is a justification right here. So basically, for conventional in the first release of August and the reason why we plant organic watermelon a little bit late, and that's counterintuitive, because you would think, well, if you plant it late, you're going to be running right into where everybody else is leaving their fields vacant for disease, watermelon fields, a lot of the growers will leave their fields and it's a source, it's a vector for disease. Sometimes that work on a research farm, it doesn't really work out for us too well unless they've incorporated most of the research fields around us. One out of four years, we got pretty bad with foliar disease, but that was about it.
And so here, we have conventional watermelon first three weeks of August at $10 a pound and this is actually basically after the surge in that one year. And I think typical prices are between 16 to 18 cents a pound, somewhere around there. And so for organic watermelon that year, at the distribution point, it was actually 48 cents a pound. And so that was over four times what a conventional grower was making. And so that justified the additional cost labor and so on and so forth and would still come out ahead and overall net for that crop. And so for us, so we did for typical watermelon, it all depends on your spacing and your density plants per acre and the variety and all. But for us, we used eight-foot spacing between beds, three foot within row spacing, we used 80 units of nitrogen, organic nitrogen pre-plant, which is a blended product from Nature Safe, 10-2-8, 10% nitrogen. And so we use something like that shank that we saw earlier where they were planting cabbage into that cover crop.
And so the shank is basically it's a fertilizer gas drip tape shank that can actually do all in one path. And we've modified it a little bit so it basically kind of opens up a [inaudible 00:27:50] and then closes back. So basically, so we subsoil pre-plant fertilizer into that [inaudible 00:27:58] and then we also put a drip tape in there. And then so that was our 80 units. And we drip fertigate two weeks post crown set.
So as soon as we got our first crown set, two weeks, we started our two pounds per acre per week of sodium nitrate and four gallons per week of Nature Safe 241. All right, excuse me, Nature's Gem 2-4-1, so a liquid fish product. And in the fall prior to that, we actually planted Regal ladino Graze, RegalGraze ladino clover, and instead of the 12 pounds per acre, we used the 25 pounds per acre to which not everybody can do, but we did it in excess because that one of the field that we planted in that year had a lot of wetting areas. So we wanted to make sure that we tried to avoid that.
And then we used a wildflower mix and we screened 22 different lines of wildflowers and our entomology, we had an entomology student, and that student categorized what bees visited the wildflowers and the watermelon crop at the same time. So they would go to both. And so basically, the idea behind that is to provide for pollination services for the crop. And that was another takeoff of using native bees versus honey bees. And we'll look at that just in a little bit. All right, so we also tested grafted versus non grafted watermelon and we also used 12 different lines of watermelon, ranging in earliness, and sweetness, and packing, and a good representation of the market. These are our four wildflower species that we use, coreopsis, godaria, cosmos, and zamias. And those were the ones where honey bees and all the other bee species would visit that and also the watermelon plants.
And so there's a lot to speak about in this slide. So we've planted... This is all that RegalGraze ladino clover, and this whole field was planted to this clover. And you can see actually we have a shank right here and the clover's grown back over that shank for the most part and it's still creeping this way. And before these watermelon plants right here. So this is one plot. So before this plot and each row is a rep. But by the time these watermelons binds crept down into the alleys and you can see it's moist on this side right here, that's where the drip tape was placed more so on that side and you can see it's on more so on this side. So where it was wet first, the clover actually did creep all the way back to the edge, providing a place for the binds to adhere to and pull the watermelon crop apart from that.
This actually worked, when I said earlier too good, the cover crop worked too well. So without having anything to keep the clover from coming back, we actually... You can see there's like baby transplants down here. This is our third time planting those and opening these holes back up. So we went to burning a whole of clover to allow time for the watermelon crop to actually emerge and start competing. But the clover actually still out-competed the watermelon in these scenarios. So we've got to go back and actually decide how we're going to fix that, how we're going to actually address the competition factor of that, that clover, while still maintaining a weed-free environment between the rows because we spend so much time turning vines and also controlling weeds through cultivation and tillage. This basically eventually opens up to the entire door for just a greenfield.
And we also have wildflowers planted along these borders. And so we never had to use insecticides and we just basically used copper and we also use sulfur products. And primarily, the environment itself kind of took care of itself as far as pest disease. And the grafting, of course, proved to be better yielding, although grafting was typically around 10 days to two weeks later than the ungrafted watermelon. Grafting did prove to be higher yielding, sweeter, pretty much across the board almost on all varieties. So this is what... This is just an aerial view of the field and then this is basically... This is a picture of the field and this is the end of the field where you have nutsedge and other grasses popping up. But for the most part, the field's pretty clean where the beds were. Okay? And typically, you would not be able to see that if the clover was not there. The whole field would be completely grassy looking like this.
So you can see it, it actually works extremely well. And then the wildflowers provide for plenty of pollinization services as well as act as a banker crop for parasitoids like lady beetle larvae and wasps and things of that nature. And so this is another picture of the following year. Like I said, once again on the end, you have the grasses where we destroyed the clover and allowed the grasses allowed to come back. We did a study in this field prior to this for three years and we found that the inclusion of this method can reduce yellow nutsedge numbers by 70% after two years of rotation in the cover crops. So essentially, where we had clover in these alleys before, we would have clover this year and we would take this and we would plant two crops in this bed and we would plant a crop in this bed and then harvest it and then go back and plant another crop in that bed for the whole year.
And then the following season where you see plastic now is where you would see clover. And then where you see alley now is where you would see plastic the following year. That's where we derive at the two-year rotation for eliminating the yellow nutsedge. And this is just a picture of... And so there was a little bit more soil disturbance in these flower beds because there's two rows really close together. So we ran two shanks. And by doing that, we disturbed the soil a little bit more than we did in where the watermelons were planted out here. And so you can see all these grassy species that have actually kind of grown up and really competed with these flowers. But we got the flowers in early enough where they were able to ultimately outcompete.
So it was kind of hard to determine which draft we put on here, but this is just pollinator services. So these are the different species of bees. And so you have your Apis species, which are your honey bees, your small halictids by far were the total number. And then you have your Bombus species. And one of the reasons why, so we see when it's really humid and it's really dewey and on the ground, a lot of our... We have about, I don't know, maybe 50 or 60 hives on the station, but when it's cool outside or if it's wet outside, the honeybees don't typically like to come out too much. I mean, only when ideal conditions. I mean, but the bumblebees were really the... As far as the number of pollinization visits and services, basically, the bumblebees down here were actually doing a lot of the heavier lifting in environmental conditions when the environmental conditions were not conducive for honey bees.
I've seen honeybees out there basically hiding in the field inside of flowers, still working, when it was thunderstorming on them. And they just continually work, just keep on working. So that was basically you saw a very large increase in... And the one interesting thing is though that you see is that the grafted material, the ungrafted material the halictids liked. And everything liked the ungrafted material except for the bumblebees. The bumblebees actually like the grafted material over the ungrafted material, which was pretty interesting. And some had said maybe it's has something to do with the color difference that we can't see that bees may be able to see that happens during that grafting. Maybe aromas in the air. Just don't know yet. That's another entomology project.Mackane Vogel:
I'd like to take a moment to thank our sponsor, Montag Manufacturing. Montag precision metering equipment is helping producers achieve their yield goals while saving on seed and input costs. For establishing cover crops, Montag's family of seed platform equipment adapts to a variety of major brand delivery systems that will conserve seed and nutrients along with soil and water. Explore new options for your production and conservation goals with Montag dealer. Visit montagmfg.com or call Montag at 712-517-2775. Now, let's get back to the conversation.Brian Ward:
And the reason why we need pollinization services in watermelon and why the wildflowers and maintaining wildflowers is easier than maintaining bees and the danger of hurting honey bees from other fields or whatever, is this is one sign of inadequate pollinization that happens with... There's other symptoms, but this is a virtually healthy watermelon here. You do see a little bit of cracking right here and that's just called hollowheart, but that's actually basically not existent. That could have been just dropped and little crack. Same with this one. But when you start seeing these linear lines like this, then you're starting to get to a little bit more pre hollowheart conditions. So pollinization services and organic best reduction is important, but also being able to incorporate those pollinization services within the cover crop system is also important. And I also do grow peanuts and other road crops as well.
And with that, I just want to thank the USDA NIFA for the grant. And like I said, this is just a brief overview of what we do and how we're doing it and how we're still trying to perfect this and also moving forward to this carbon credit thing and mitigation and green and climate smart crops, this type of work right here, hopefully a lot of you will actually be able to utilize, hopefully a lot of you will be able to modify and maybe take some lesson here and just think outside of the box and see how you can modify your habitat, maybe get credits down the road when those become readily available. I just want to say thank you in allowing me for me to speak today. And with that, I can take questions or proceed from there.Speaker 1:
Great. Well, thank you, Brian. That was quite a lot of information. So I was taking some notes as we were going. And I have a couple of questions for you and I'm sure that some of the attendees will be sending some questions in as well. But I guess I have a couple of questions. You had said earlier, early in your presentation, and I think what you said was sometimes cover crops do too good of a job of controlling weeds. Did I get that right?Brian Ward:
Can you just explain what you mean by that?Brian Ward:
Well, so when we were transplanting the watermelon into the cover crop scenario, so the whole field was planted in clover. So the whole field planted in clover, and it stayed like that for three, four months. And then just where the plastic was and where we stripped just till just that area for the plasticulture. And then in the clover between the plastic is where we ran the shank, the subsoiling shank for the watermelon. And we also took and burned with a flamer little spots in a circle around where we were going to plant the watermelon transplant. And so when we did that, the watermelon plant grew fine, but the clover... So there was a 12-inch circle around the transplant and I knew that the clover would... It's so aggressive that the clover would creep back into that, onto that soil, excuse me, onto that soil and reestablish itself. It just happened a lot more... It happened faster than what the watermelon could outcompete the clover and therefore, the clover basically swallowed up the transplant.Speaker 1:
Oh, okay.Brian Ward:
And that's why, so it worked too well. So basically, at that point, the watermelon became a functional weed to the clover.Speaker 1:
Oh, okay.Brian Ward:
So that's one of the parts we have to work on with trying to get away from plasticulture altogether is how to pick the right specific cover crop for that, let's say for watermelon, in order for the watermelon to compete. And the same scenario has to play out for, if you're going to be doing bare ground broccoli or bare ground okra in the summertime or whatever scenario, you just have to basically match this living cover crop with the ability of your crop to outcompete it.Speaker 1:
Okay, gotcha.Brian Ward:
Did that answer your question?Speaker 1:
I think so, yeah. And then I was also really curious to just have you explain how and when you put that plastic down, how wide is it, when do you do it? And then I guess I'm also curious about the machine with the shank and the drip tape. So I'm curious about what the setup on that machine is, or is the shank running next to... It looked like it was off to the side of where the row was going to be.Brian Ward:
So the shank... So it all depends. So it all depends on who makes the equipment. So the equipment we have is called Kennco, is the name of the corporation that manufactures that. There's also Rain Bird makes equipment, and there's numerous, numerous manufacturers of equipment out there that have this plastic lane technology and they all come in differing widths. So I think the narrowest width, that is around 18 inches of plastic surface coverage, all the way out to about 32 inches is what we use primarily. And 32 inches, you can get a double crop on in South Carolina. Well, two rows, let's say. Two rows, sometimes three rows on that 32 inch width.
In California, their beds are wider than 32 inches, they're probably closer to 48, 50 inches with very little between row spacing. So they have the taller, skinnier tires that leave less of a footprint in the field. And so basically, whereas we leave almost half the field unplanted with soil surface exposed, that's why I wanted to use the cover crops in that area to control weeds. California, and they don't have the pressure that we have, they basically utilize about 85% of their field space with only leaving about 15% of soil surface exposed. And if they could get a cover crop in there, they would basically almost have full coverage in the field of green.Speaker 1:
Okay. And I wanted to ask you about your clover that you were talking about. So that's a perennial clover?Brian Ward:
That clover, it can be. But in our heat in the summertime, and if it's dry, it'll kill it. But if we get any kind of rainfall at all, it can withstand the heat and come back that fall. And the cool thing about it is in an organic system, is that mustards and other weeds will climb through the top of it, of the clover, and then you can take a tractor like a Bush Hog and go and mow those weeds like wild radishes and things like that. You can actually mow those prior to them setting their seed. And so you can eliminate the weed seed bank by doing that. So everything will grow through the clover and try to flower and you mow it and it destroys it. And so at the end of the day, you're reducing your weed seed bank, but providing nitrogen through the legume action and carbon just through sequestration of carbon into the plant tissue itself.
And the reason we came to that one particular type of clover and now, the new Seminole ladino clover, is that back in, I think it was 2004, we did a trial on I think it was about 30 different types of clover and measured all aspects, ground clovers, I mean, everything. And we can basically boil it down to one type that could withstand tractor mowing, weeding, and come right back. So you can pull weeds right next to it, it'll pull the plant up. If it base back on the soil, it'll root right back. It's a very hardy clover.Speaker 1:
Okay. And what row spacing were you planting that at?Brian Ward:
The clover?Speaker 1:
I didn't talk about that. The clover was actually drilled in with a turf type of seeder called a Brillion. And so we use a 10 foot Brillion that essentially... And it's made for turf and small seed. And so that's how we used it. And I think the rows on the Brillion are approximately seven inches between the row.Speaker 1:
Okay, gotcha. And I wanted to ask you about the cowpeas just because I wasn't sure if I totally understood. Those are a vining plant and it seemed like you were saying one plant would cover 100 square feet?Brian Ward:
And how are you planting those?Brian Ward:
Now, those, we can do one of two things with. You can actually either drill at around 75 pounds an acre with a traditional drill, or you can broadcast at about 110 pounds of the acre. And then actually, just broadcast it on the soil surface, and then essentially either using some kind of a leveling, smoothing tool to incorporate the seed, or you can actually just disk the field after you broadcast the seed. And the seed are very hardy. But they're resistant to nematodes. So if you have a field that's notorious for nematodes, you can plant the clover. I mean, you can plant the 1136, 1137, 1138, not have it come back, but also have it not be a vector for nematodes. So you won't be increasing the number of nematodes, but you won't be sponsoring the population on nematodes either.Speaker 1:
Okay. And you had kind of talked about you're not really using the cowpeas that much anymore. I think that that's what I took, that's what I understood. And mainly because you like the Sudan better?Brian Ward:
Oh, the sunn hemp. I like the [inaudible 00:48:50].Speaker 1:
The sunn hemps. Sorry. The sunn hemp. Right. So are there certain conditions or situations where the cowpeas would be a better choice?Brian Ward:
Probably for... I would say the cowpeas would be a better choice if you're doing ASD technology, which is the anaerobic soil disinfestation technology, or really, I mean, they both have the same characteristics, sunn hemp and... They both cover the ground really well. It's just for a cover crop, they're equally as well as a cover crop because they both outcompete weeds, retain soil moisture, add carbon, add nitrogen. It's just what happens to it after it's crimped or killed is the issue. The sunn hemp just makes a much better conducer of... It's better, it's more conducive to a crimped no-till situation whereas the cowpea disintegrates faster.Speaker 1:
I see. Okay.Brian Ward:
And I mean, you're left basically just vines on the soil surface versus [inaudible 00:50:04].Speaker 1:
Okay, I get it.Brian Ward:
Sunn hemp creates more almost like a wall and you're just laying the wall down. You're [inaudible 00:50:11] through a little hole in the wall.Speaker 1:
Yeah. Okay. That makes sense. So I'm glad you brought up that ASD technology. That's anaerobic soil... What's the D word?Brian Ward:
Disinfestation. And why do you want to sterilize the soils?Brian Ward:
So in vegetable production, for years and years and years, part of the normal practice in conventional ag was to use soil fumigants. And actually, and we still use soil fumigants, but the best product that worked was methyl bromide. And they started phasing that out a long time ago and I think it's completely phased out or almost completely phased out completely. And so that was a normal process to sterilize your beds. And so you were almost like treating your bed like a hydroponic media.Speaker 1:
I see.Brian Ward:
So in that whole... And so you got to look at ASD as not one tool, but part of a system. And so part of that system is sterilizing the bed, and then in an ideal situation, is going back and actually putting a drench or some kind of a granular sporulated product that contains a lot of your beneficial organisms. And then you repopulate your soil.Speaker 1:
So basically, all you're doing is taking away part of your negative aspect, but the data shows from California and Florida that actually, the pest diseases, the pathogens in the soil, the soil-borne pests actually have a higher reduction rate and recovery than do the beneficial bacteria. So you're not going to kill everything, but the beneficial bacteria come back more hardy and in greater numbers and do the pathogenic bacteria and [inaudible 00:52:19] and so on and so forth.Speaker 1:
Okay, that's interesting. And then you were kind of talking about you have bare ground plots and you've got the mulched plots and you've got the plastic or the... Yeah, with the plastic. So have you compared yield results between those three systems, and if so, how did they compare?Brian Ward:
The yields were fairly similar across the way. The plasticulture did add earliness.Speaker 1:
Added what?Brian Ward:
Earliness. Okay.Brian Ward:
So you got a early... The brocco crop coming out of that was early. So we're looking at seven to 10 days on earliness.Speaker 1:
Oh, okay.Brian Ward:
And actually, that was reduced. The next level of earliness was on the bare ground, and then the mulched. So actually, the mulch, the organic green manure mulch, the pulverized cowpea that was left on top actually kind of acted out as a insulating blanket. So the soil temperatures didn't oscillate as much as they did in the plastic, but they didn't stay as warm as they did in the plastic or the bare ground. And I think that's just direct sunlight contact with the soil surface and with the plastic surface, which basically conducted that energy downward. So earliness was effective. So not necessarily in a positive way, but yields overall, were as good.
The bare ground proved to be the worst yields. And then the plasticulture and then the bare ground green manure cover on top, those were about similar. So you're getting about the same effect from both, from either. So ideally, that same method would be where we would want to go to modify a no-till situation. And there's sugar esters and some other polymers, organic polymers that you can add to that and actually create a binding agent to bind the carbon and the cellulose together and act as a... Have a longer longevity to that mat, that organic mat that's resting on the soil surface to prevent weeds. And so that's some stuff that I want to get into and look at further down the road as well.Speaker 1:
Yeah, okay. Yeah, and the bare ground system must have had more weed pressure?Brian Ward:
Oh, absolutely. So that was the labor. Yeah, so that's where you didn't have labor in the other two for pulling weeds or dealing with weeds. And then the bare ground situation, it was all... Most of your... I mean, that's where you break... That's where the magic number is, is in that labor. That labor cost of weed. Everything else is mitigatable. You can mitigate almost everything except for weed pressure. Weed pressure is so horrible in organics. And we have a weed scientist at our station that is a good portion of their work is devoted to ASD technology and weed science and sustainable systems. And so I work closely with this person.Speaker 1:
And you had mentioned yellow nutsedge. Is that the primary weed that you guys are battling there or are there others as well?Brian Ward:
There're numerous, but that is one of them, one of the main summer weeds. Purselane is another weed. Of course, our pigweed is really bad. And of course, all of our grasses are really bad, but the clover in the summer situation. So we plant the clover in October and it grows until March. And then we cut a small strip for the placement of fertilizer and drip and put the plastic down. The clover grows back to the plastic, the watermelon vines out and spreads a lot faster, produces more. Spreads a lot faster and also a lot of times in organics, organic watermelon, the vine, you'll get some vine decline and you won't have a really good canopy.
And the watermelons in those scenarios that are not covered well typically get sunburned and become non-marketable. And so by sitting in a 18-inch layer... So 18 inches, so the watermelon's actually kind of high down and are covered from... They actually rest on top of the clover and they're hidden by clover and the vines are as well. And so I've never seen in my life, ever in my life, the population of beneficials and just a perfect balance. I mean, absolute perfect balance in a whole system approach. It works out really well.Speaker 1:
Mm-hmm. Okay. And then just one final question. You had talked about grafted versus ungrafted. Can you tell me what are the watermelon plants being grafted to?Brian Ward:
Okay, so that's another big part of the research we do at our station is watermelon research and grafting technology. And so early on, interspecific hybrid squash were the varieties that were typically used. And that was primarily used for fusarium resistance. We're resistant to soil-borne fusarium fungus. And that's the fusarium oxysporum. And so our pathologist, working with our breeders, have come together and they've done wild watermelon rootstocks, they've done Lagenaria, which is bottle gourd. So we had interspecific squash hybrid, we have bottle gourd type hybrids, we have wild watermelon hybrids. And the wild watermelon hybrids, or the wild watermelons varieties are the ones that we're working with now heavily. We've actually eliminated the other ones because the rootstock now of the wild watermelon has resistance to nematodes and fusarium. Okay?
So that's what we graft too. And we graft either seedless or seeded watermelon on top of that. And the reason why we do that is because for soil-borne disease. So about 90% of the world's watermelons are grafted except for the United States where labor is expensive. And so we've developed robots to do that. And so we have robots actually do the grafting, or we also have hand grafting still in the United States. They're a little bit more expensive, but you don't have to worry about the disease so much. And so, I don't know, did I answer your question or am I rambling?Speaker 1:
Yes. No, you answered the question. That's very interesting. I've learned a huge amount from this short presentation, so thank you.Brian Ward:
I wanted to be, like I said, if I were to flip through slides the entire... I mean, flip the data the entire time, I can get that data to you, but right now, I want to just to present the concept.Speaker 1:
Sure. Yeah.Brian Ward:
So ASD relies heavily on carbohydrate or carbon to ferment essentially in the soil. Grafting, bottom... The take home from grafting is that it's not for every rootstock and every scion, which is the top. Every combination is not going to work well in your area. So that's where the research in your area is going to decide the best combination to use. But grafting, so the cool thing about grafting a watermelon in an organic system or an e-system is that when typical watermelons are ready to be harvested, there's maybe a three-day window of optimum time. And whereas a grafted watermelon can sit in the field for 10 days, and so it has a longer...
So if it's raining, downpouring or whatever, or if you just can't get people from another field into that field to harvest, you have a little bit more of a window, a little bit better timing to play with. Typically, watermelon, there's more yield per plant for watermelon, meaning more yield per acre. Lycopene content is typically higher in grafted watermelon. So basically, you get a lot of benefits. And one of the most important things is disease, soil-borne disease control.Speaker 1:
Yeah, okay.Brian Ward:
Amazingly enough, there's a phenomenon occurring in some situations where when you graft a watermelon, say a seedless watermelon on top of whatever rootstock it is, something's happening at the graft junction where signals somehow are going from a squash or a wild watermelon or a bottle gourd traveling because they're the same family or traveling up into the scion material up here and actually potentially turning on genes in the scion material that basically code for secondary metabolites like melatonin and things of that nature.
So there's really interesting things going on with grafting broccoli varieties that are well suited to the heat and actually would benefit from a summer cover cropping system that you could carry through the clover in those scenarios, and the broccoli could actually add as a shade factor to help mitigate some of that summer stress of the clover. So there's so much. There's so many different ideas, different takes, and so much still to perfect, but at least the audience may have a thought now, they say, "Hey, I can do that on my farm. But maybe it's slightly different. I'm using maybe a slightly different cover crop, but it'll work well in my area." Say in Washington or Kansas or wherever or [inaudible 01:03:27].Mackane Vogel:
Thanks to Brian Ward for today's discussion. The full transcript and video presentation are available at covercropstrategies.com/podcasts. Many thanks to Montag Manufacturing for helping to make this cover crop podcast series possible. And from all of us here at Cover Crop Strategies, I'm Mackane Vogel. Thanks for listening.