Talkin' Crap

Cold Weather, Hot Topics: Winter Manure Management

• Dan Andersen • Season 1 • Episode 12

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In this episode of Talkin' Crap, Dan Andersen and Luke Soko discuss the challenges and best practices for winter solid manure application. They highlight the risks associated with winter manure application, such as nutrient movement due to frozen or snow-covered ground, and the importance of following state regulations. Find show notes here. 

Dan Andersen:

Music. Hello and welcome to Talkin' Crap, a podcast by Iowa State University Extension and Outreach. This institution is an equal opportunity provider for the full non discrimination statement or accommodation inquiries, go to www.extension.iastate.edu/diversity/ext. In this podcast, we discuss insights into the science technology and best practices surrounding manure management. Our objectives are to build awareness about the challenges farmers and the broader agricultural industry face around manure and to demonstrate solutions in areas of innovation. Hello and welcome back for another episode of Talkin' Crap. I'm your host, Dan Anderson, associate professor and extension specialist in the ag and biosystems engineering department at Iowa State University. Today we're going to be talking about winter manure application, why it matters, and how to follow some best practices about it. Today, I'm joined by Luke Soko. Great to have you here today, Luke.

Luke Soko:

Thanks, Dan. It's great to be here. My name is Luke Soko I'm a PhD student at Iowa State in agricultural and biosystems engineering, and I work directly with Dr. Dan Anderson. Today we're talking about winter manure application for cattle operations.

Dan Andersen:

And it's a topic you're excited to learn a little bit more about. I sprung this a bit on you at the last minute.

Luke Soko:

Absolutely, I feel like I'm getting a front row seat to like, a documentary. I'm excited to learn about this.

Dan Andersen:

A documentary. So you're hoping for March of the Penguins, except manure style.

Luke Soko:

Yeah, I suppose. Doesn't have to be too historical. But yes, I'm very excited to learn about it.

Dan Andersen:

Or narrated by Morgan Freeman. All right, so let's get started. As you've seen, we've had a little bit of snowfall already this year, and anytime we get a little snowfall, I think it's time to think about, what are the rules for winter manure application, who do they apply to? And then what are some best practices for what we can all do to try and minimize the risks associated with manure application when we have some of those winter conditions arrive. So the first thing to think about is, why would winter manure application be more risky than any other time? And as you think about that, Luke, what is your reason? Why wouldn't we have to be more careful in winter than other times?

Luke Soko:

Well, if I had to guess, frost, the ground is slippery. Maybe we have a sloped ground and we have a slippery ground. We have a liquid manure draining into waterways. And we also don't have a lot of vegetation, not a lot of microbial activity, so I don't know how the degradation of that manure was going to work out, necessarily.

Dan Andersen:

Yeah, and that's those are some great points, and I think you hit on it with the first one, when you were talking about snow covered or frozen ground. Well, if there's snow and we melt that snow quickly, there's a chance for more water. More water just means more movement. And if we have soil that gets frozen, frozen with water in it, it's harder for the water to work through the soil pores. So when we think about manure application, our goal is really to get that manure into the ground, into contact with the soil, and hopefully absorb some of those nutrients on the soil particles. And if it's frozen and harder for manure get to get in the ground, that's exactly the situation we're going to see. One that I liked, you mentioned slippery. You think about slipping and falling on the polished sidewalks around the campus sometimes, right when we drive that polisher around.

Luke Soko:

Absolutely.

Dan Andersen:

And in manure systems, if you have frozen soil, but it gets warm enough to melt on top, we can get some slime, and it can be hard to get some traction, but more so we're worried about getting that manure into the soil and moving around. So there's been a lot of people who've done research on frozen manure. More power to them. It's definitely a harder time of the year to manage. I managed flumes for some runoff projects for a while, and thankfully, I didn't have to do much during the winter. But if you are using a flume to measure what's coming off in the winter, you need to make sure you're getting it shoveled out, getting the snow out of the way. These flumes work by holding water in them, and if there's snow in there and it's backing the water up, your measurements don't work. So it's hard to do research, good research on snow covered ground, but there have been people who've done it. And I want to start this out by pointing out it's riskier, but riskier doesn't mean we'll always have movement, and that's sort of what the research has bore out. Some of these studies say, Wow, we had astronomical amounts of movement, often from one or two runoff events that occur. And others look at it and say, the amount of nutrient loss that we had is similar to when we put manure on in the fall, but the chance of having that larger nutrient movement event is bigger from winter manure. We just have a greater probability of happening, of it happening. And there's a few times that it's more prone to happening. If we get snow and it melts really rapidly, that's a chance where, especially if the ground still frozen underneath, we just have more of that surface runoff, more chance for nutrient transport. If we have a frozen soil and we get a rainfall event, especially a larger rainfall event, like an inch or more, most of that water tends to run off in the winter. If we have that same event in summer or spring or fall, it tends to soak in we've seen a lot of rainfall this fall, almost all of its exclusively soaked into the ground because we're so dry going into it. Winter we often don't have that luxury.

Luke Soko:

How does, how does tillage play into the role of whether we have manure draining or not draining or if it has any impact?

Dan Andersen:

Yeah, so there's a lot of competing factors there, and we'll talk and put more about this at the end, when we talk about some best practice tips. But that's a great question. So if we can still do tillage, the soil isn't frozen. So your question is more really, if we tilled in the fall, we end up with a field that we still want to put manure on, it's now froze, what should we do? And there's a couple things happening. So tillage increases surface roughness of the soil, right?

Luke Soko:

Yep.

Dan Andersen:

So you can think about, if that happens, maybe that's a good thing. We're ending up surface applying the manure. There's this small surface roughness, and we can catch some manure basically in our tillage bands, and it has more time to soak in before it could run off. And that's a good thing, right? I mean, that's essentially what we've wanted to do. When you think about following the contour of the land when we do a tillage operation, perfect approach, right? So if it's contoured, and we're doing that, good chance for that water to sit in the contour, soak in before it moves on. If you till up and down the hill and do the same thing, and the water's slower about soaking in, the manure is slower about soaking in well, if it's on the hill slope and we're up and down, we've essentially made a little channel for it to flow in, and it might not be as helpful, but there's this competing factor on this, especially when we're talking about snow rather than just frozen ground. If that surface is rougher, do you think it catches more snow or less snow?

Luke Soko:

If it's a rougher surface, more.

Dan Andersen:

More snow, that's absolutely right, and the snow is part of our water source in this case. So if we have that snow caught on a rougher surface, and it then gets liquid manure put on it. We're gonna have the liquid manure that we added, plus that snow we melted from putting liquid on it, right? And that might make it riskier. Then we can get even more complicated. Does the snow stick around longer on black dirt or on the grass?

Luke Soko:

The grass?

Dan Andersen:

Why is that?

Luke Soko:

Surface area?

Dan Andersen:

Surface area a little bit, but it's also about temperature effects, right? So black will absorb heat, and the grass turns this sort of light brown, terrible at absorbing heat. So there's this temperature dynamic that comes into play, and it's complicated there. Certainly we know that darker surfaces absorb heat more readily from the sun and will warm up faster. So if you think about a white, snowy field and the sun shining on it, it's reflecting a lot of that energy, right? That's where you get the glare, and you still wear your sunglasses in the winter.

Luke Soko:

Yeah, yeah.

Dan Andersen:

Yeah. So when you think about that, it's reflecting a lot of that energy. If we have something that's darker, like we put solid manure or liquid manure on the top, and change the color so it looks dirtier, it'll absorb more heat and melt more rapidly. And sometimes that's good, sometimes that's bad, right? If there's very little snow and we melt it, okay, we should be fine. It should still soak in. If there's three, four inches of snow and we do the same thing, and we melt it all in a day, well, that's a fair amount of water, a quarter of inch of water, that we added to whatever we're putting on there. So all those factors compete, and it makes it hard. I think normally, when we talk about this, or when I think about what we should be doing, you're looking at the field and saying how much snow is out there to start with, or how deep is the frost as we're starting or how much water was in the ground when it froze, and trying to assess the risk of, will it infiltrate or will it run off?

Luke Soko:

That's interesting.

Dan Andersen:

All right, so I think where I'd like to start on this is the regulations, and I think first of all, regulations vary by state, so we're going to be more specific to Iowa regulations when we talk about them, but most states do have some sort of regulatory process.

Luke Soko:

What about and for the winter? Is the winter defined differently for southern states, as opposed to maybe Wisconsin and Minnesota?

Dan Andersen:

Yeah, so some states might not even have winter manure rules. So when we think about what winter manure really means, it's probably meaning something like frozen ground or snow covered ground.

Luke Soko:

Okay.

Dan Andersen:

So if you go to a southern state, like North Carolina or further south than that, yeah, the risk of freezing, of actually dealing with some of these conditions, is much, much different. They might not experience them. So the way you'd write a rule, or how that rule would come into play is much different. So absolutely, that's one of the reasons why I think looking towards state, state specific rules is probably useful on this topic. Writing a rule for Wisconsin and saying this applies down in Texas just doesn't make any sense.

Luke Soko:

Yeah. How do they define winter for Iowa?

Dan Andersen:

eah. So I think that's a great question. The first thing I want to say there is our winter rules only apply to liquid manure, not to solid manure. That doesn't mean our best management practices shouldn't occur for both but our rules are specifically written for liquid manure, and that's because a lot of the research in Iowa that has been done bore out that that liquid manure was more risky to apply in the winter, and we haven't seen the same effect with solid manure, probably because of the percentage of nutrients that are available, or mineral right at the time of application, relative to how much of it's bound in organic form. With many of our solid manures, they're more organic, so they're not as soluble or movable with liquid right away when we apply them.

Luke Soko:

How much solid manure exists relative to liquid manure in Iowa?

Dan Andersen:

That's a beautiful question, and it's hard to say exactly. We don't have great demographics on every operation, but we can say things like, probably most beef cattle farms are using solid manure. Certainly some are switching over to deep pit finishing barns, but most of them are solidmanure facilities, and then our poultry facilities are solid manure. So if you think about it, sort of how much of our nitrogen are we getting from manure? We're probably in that 85% liquid manure, 15% in solid manure, if we move to phosphorus, though, we might be more in that 30% coming from solidmanure, 70% is coming from liquid manure range, just because of the manure properties that we have out there. And in terms of volume, I don't like to do that. One's a mass basis, one's a volume basis. It's hard to compare them in a meaningful way. Yeah, all right, so getting back to the rule in Iowa and how we define winter, our critical date for liquid manure is December 21. If you get to December 21 and there is half an inch or more of ice on the soil or an inch or more of snow on the soil surface, we're defining that as snow covered ground, and that's sort of the demarcation that we're using. So it's both a date and a condition in Iowa. That December 21 date is really when the trigger comes in and then having that snow or ice on the ground to make it so that we are in that snow covered situation. That's what we are thinking about when we mean winter manure. If you're before that date, some years we might have snow on the ground. Some years we might not. But if we do have that snowfall, we haven't triggered that key date. Probably because generally, when you look at Iowa weather, on average, the soil isn't necessarily frozen, or our risk of that snow being there for extended periods of time is relatively low.

Luke Soko:

Okay. And who regulates this?

Dan Andersen:

It's regulated bythe Iowa DNR that it's their regulation that set this up, and they're the ones that are in charge of enforcement. But that's the key date as you go through the winter. There's some other dates that come along. For instance, on February 1 we move to a frozen ground situation, right? And most of the time the ground is frozen in February, but that's the key date that they're using there. When we hit that February 1 date, it doesn't matter if it's snow covered or not, if it's frozen, which it probably is, we'd also be prohibiting liquid manure application, and then those stay in effect until April one. So on April one, those come out of effect, so the condition doesn't matter anymore. That doesn't mean you can get out there and apply if the ground still frozen, you're probably not out there doing it. If it's snow covered, we're not there doing it. But the Iowa laws are really written from December 21 to April 1 for that snow covered, which was an inch or more of snow, half an inch or more of ice, and then the frozen ground is starting on February 1 and last until April 1. And that's the part of the year where we're really focused on Are the conditions right? And we're trying to limit the amount of manure that goes out in the field.

Luke Soko:

Okay. How do they define a frozen ground? Because I can imagine you can have a few hot days in a row and still have that frozen ground.

Dan Andersen:

So frozen ground is basically defined as being impenetrable with the soil tillage implemented. So if you can go out there and use your manure injector and get the manure covered and in the ground, or do an incorporation, which really means roughly the top four inches of the soil, and get the manure covered that wouldn't be frozen. Now we want to use our best judgment on that. If you're out there with a sweep and you're bringing up large chunks of soil because it's still frozen in chunks, and you're just fracturing the soil that's probably still a frozen soil. You're just able to run a and implement through it and and break it up. But it's not working or functioning the way we want it to, to really get good manure coverage or incorporation, but that's really what it's defined as, being impenetrable.

Luke Soko:

Okay, interesting. So what are the restrictions outlined in the NPDES? And also, what is, what is the NPDES?

Dan Andersen:

So the winter manure application rules there apply to anyone who is a confinement feeding facility if you have an NPDES permit, that's a National Pollution Discharge Elimination System permit, and that only gets used on certain facilities. The ones that I think about the most are something like an open beef feedlot. In Iowa, our confinement so under roofed facilities are written so that they can never have a discharge. The NPDES system allows discharges under certain environmental conditions. And if you think about a confinement facility like a deep pit swine barn, the weather doesn't have a major impact on how much manure I'm going to generate, right? It's the animals in the barn consistently excreting that that generate my volume. I can size my manure storage to handle what I think they're going to excrete. On the other hand, if I move to an outdoor facility, especially, say, a open feed lot, where the cattle are outside, not under roof, every rainstorm is generating some manure, water, essentially right from the runoff water, and the volume gets much harder to predict, and we had to set a standard for how much rain do we need to get before we can't reasonably expect that farm to hold all the runoff water they generate. So those facilities sometimes will get an NPDES permit for protection, so that if we have this big storm, a storm that we don't expect to happen very frequently for Iowa, 25 year, 24 hour event. So a storm that we expect to last 24 hours, that occurs once in every 25 years, which is roughly a five inch storm. If we would get an event bigger than that, so we got seven inches of rain instead of that five and change rain within 24 hours.

Luke Soko:

Within 24 hours.

Dan Andersen:

Yep, those facilities would have permission to discharge.

Luke Soko:

Okay.

Dan Andersen:

If you have one of those, they often

Luke Soko:

Discharge where?

Dan Andersen:

Well, discharge from the manure storage.

Luke Soko:

Okay.

Dan Andersen:

It would be allowable to have an overflow from their manure storage. Now, most of the people would have some sort of vegetative buffer around their manure storage, or somewhere that manure would flow before it gets necessarily directly to a stream. But it would flow towards the stream if it was discharged, and that's why we're setting the standard pretty high. It's a pretty low probability of having that event.

Luke Soko:

Yeah. Yeah.

Dan Andersen:

and your manure storage probably would be have if we would just apply manure and our storage was to be pretty full when you had that event in order for actually empty, not going to overflow from that event, even though it to turn into a discharge. So just because you have that event doesn't mean you would have a discharge, right? would technically be allowed. But if you have one of those permits, they are often written in with other more stringent regulations related to your manure best practices. One that they'll often write out is that all manure application in the winter is prohibited. So it doesn't matter if you have liquid or solid manure, they could write into that permit that we aren't going to have you applying solid manure during the winter. They're operation specific about how they're written, so you just have to pay attention to what does your operation say, and is there a limitation on if you're allowed to put manure on the winter. There's a similar program with NRCS, where they might help you with a Comprehensive Nutrient Management Plan. If you've taken costs here to help build the manure storage structure, you often have this practice written up. It's their 590 Nutrient Management Standard, and that would often limit winter manure application as well, because we know it isn't the best use of manure nutrients, but sometimes it does happen that we have to apply some manure in the winter.

Luke Soko:

If I were a farmer that applies manure in the winter, you know, fairly, you know, often, year by year, how do I change my operations so that I'm applying in the fall or spring, which is, I mean, typically more common, I believe, correct.

Dan Andersen:

Yeah, definitely more common. And especially in Iowa, where we're with deep pit barns, we don't actually see them applying manure in the winter unless they have an emergency situation, a water line broke. So most of the people doing winter manure application tend to have a storage that's full, where they need to do something to minimize the chance of that manure storage actually overflowing. And we think about that, I would much rather have you putting the manure onto the field in the winter, rather than letting your manure storage overflow. We know that if you put it on the ground, we're going to reduce the amount of volume and at least some of the nutrients that are lost from that. If we have a direct overflow from our manure storage, and it makes it from a ditch, chance is it's probably going to flow towards a stream and eventually get there, right? So land application is better than having a manure storage overflow, without question. Perhaps one of the more common places we see this winter manure application is with small dairy farms, where they don't have that manure storage. So when you think about manure storages are expensive, you've seen some of this in your work on costing out anaerobic digestion systems.

Luke Soko:

Yeah.

Dan Andersen:

So sometimes a farm would have built a manure storage that doesn't have six months of storage, and that means they might not be able to make it through the winter. At a bare minimum, you probably need three to four months, given Iowa's climatic conditions. If you're in northern Iowa, you probably need those four months, but you can start pushing on windows, and if you don't have sufficient storage, that tends to be where we see some of this winter manure application occurring, especially on the liquid side.

Luke Soko:

Is it, Is it difficult to get a hold of manure applicators in the winter?

Dan Andersen:

Well, it's not their busy season, but it's also not a fun time to be applying. So I don't think it's difficult to get a hold of them, but it's sometimes difficult to find days that are really suitable for moving manure around. And it's definitely not fun conditions to be outside.

Luke Soko:

Yeah. Okay.

Dan Andersen:

So I think that's the struggle. They're also tailored. I mean, most of our equipment is set up to be injection, right? So if we're gonna have to switch to manure all of a sudden, we have to use just leave our equipment up and put it on the surface and operate it a little bit differently. But it's possible to find manure applicators in the winter. It's just not the preferred and they're gonna have to use their equipment a little bit differently to accomplish the job.

Luke Soko:

Okay.

Dan Andersen:

So I think the big first thing to think about is just liquid comes with its own water, right? And that water is really our potential for a nutrient movement. With solid manure. It takes a weather event, either melting or rainfall, to have that transport mechanism there. With liquid manure, the transport mechanism is built in, right? It has that water that's our chance for some of the movement, and that's partly what makes it more liquid or more risky. The other thing that you probably want to think about is, if I have a snowball and I dip it in water, what happens?

Luke Soko:

It melts.

Dan Andersen:

It melts right. Water is pulling the heat away from that snow. Essentially, it's chilling the water down, but it melts more quickly. So if you put water on snow, there's a chance that it's going to end up with even more water. So you're increasing that risk.

Luke Soko:

What about how soon does that liquid manure freeze on the surface?

Dan Andersen:

Depends on the soil conditions the temperature outside, so it's definitely not instantaneous.

Luke Soko:

Yeah.

Dan Andersen:

But the same way you've seen people during the packer games that you love to watch, where they'll say, it's cold outside, and they'll pour a little water and say, or throw water up in the air and say, look, it freezes before it hits the ground.

Luke Soko:

Yeah,

Dan Andersen:

it's a function of how big a particle you have, right? Smaller droplets freeze faster.

Luke Soko:

Yeah.

Dan Andersen:

Big droplets fees freeze slower. So that's that's a tough question. It depends really a lot on the weather conditions. But it's definitely not instantaneous, and we don't want it to be instantaneous. If it's freezing that quick, as you're driving to the field, your lines will be icing up. You'll have some ice in your tank, right? And that's not probably greatest time to be applying.

Luke Soko:

How cold might that be?

Dan Andersen:

Cold.

Luke Soko:

Yeah.

Dan Andersen:

Really cold. Okay, so water freezes at 32 manure is going to freeze lower than that because it's loaded with salt. If you can estimate the salt competition, you can estimate freezing point depression. But freezing points of manure, given their saltiness, are probably in that 25-26 degrees Fahrenheit sort of range. If you have a more liquid manure, you're gonna be closer to that 32, if you have something that's higher in nutrient concentration, generally higher in salt, it'll freeze a little bit lower. But they're all sort of in that range. And then there's a time frame of how quickly it freezes. Sort of like when you want a cold beverage and you need the ice cubes out of your fridge, you better start it than the night before, not minutes before you need it, right?

Luke Soko:

Yeah.

Dan Andersen:

So it does take a little bit of time to freeze.

Luke Soko:

Okay.

Dan Andersen:

Freezing doesn't make it a solid manure. The other thing is, just because your manure is frozen, say I had Okay, that makes sense. a liquid manure storage, a small one outside that I was using That's why liquid manure is more risky. Just we have that basically as a stockpiling pad, and it was sloppy, and the water's supposed to drain off into a true liquid manure hydrology built into it, where we have that risk of transport. storage. If you're getting that frozen and you're handling that manure slush as a slurry and or maybe even as a solid manure that doesn't turn it into a solid manure in regulatory situations, it's still a liquid manure if it's was a liquid manure, It can cause a little bit of the snow to melt, and if it falls on top of the snow and turns it black, it can cause the snow to melt even more quickly around it to give some of that mechanism for movement. It also has more of the nutrients right away in that soluble form, so they're going to preferentially move with more of the water than maybe some of that liquid manure, where, as long as it moves slow, it doesn't pick up particulate matter, it won't have as much nutrient content. So that's really what's making the liquid manure more risky, and why it was chose to be regulated in Iowa.

Luke Soko:

Would you prefer to apply in the winter on some land that's maybe drained more efficiently than other land?

Dan Andersen:

I mean, so first we want to try and avoid winter application if we could.

Luke Soko:

Yeah.

Dan Andersen:

We're talking about, how do we choose the best of worst scenarios?

Luke Soko:

Where do we? Where do we if we have to put it somewhere?

Dan Andersen:

Yeah A couple things on that. One, we probably want to try and think about what time of year it is. Is it early winter or late winter?

Luke Soko:

Okay.

Dan Andersen:

And if it's I would prefer you to get your manure application done in early winter, when there's periods of low to no snow cover, compared to late winter.

Luke Soko:

Okay.

Dan Andersen:

And if you think about why that might be true, I'm not as worried about a large rainstorm in January, February as I am in March, April, of that next event being a rainstorm that melts a lot of snow or moves snow very quickly. The other thing is, many of our nutrients in

Luke Soko:

Yeah. manure love to stick to soil, right? Phosphorus loves to stick to soil. Ammonia carries a positive charge. It loves to stick to soil. So if we get good manure to soil contact over a period of time, more of those nutrients are going to be sticking to soil. So early in the winter is better than late in the winter if you're forced to do this. And then the first thing I'm doing when I'm assessing fields is really looking at the amount of snow cover. If I have residue on my field, and we love residue, oftentimes those fields end up with more snow cover on them. Fields that don't have residue end up with less. So I might start thinking, well, the field with less residue, that might be a better choice for me given the situation I'm just having, yeah? Even though normally we'd say the opposite of that, right, if you're doing spring or fall, we love that residue. It'll help hold some of that manure. Yeah,

Dan Andersen:

Those manure nutrients there. This is a case where maybe it's hurting us a little bit.

Luke Soko:

Okay,

Dan Andersen:

The other part of your question was sort of related to slope and drainage.

Luke Soko:

Yeah.

Dan Andersen:

So definitely, we want places that are flatter, if possible.

Luke Soko:

Okay, would we prefer to apply to a drainage system Yeah, of course.

Dan Andersen:

Not places where water will pond, ideally, as it melts, but flatters better, just because the water will move slower. And you asked about fields with better drainage, potentially, especially if we went into that winter wet, the drainage will help us have more space in that soil profile, but hold more of that liquid, hopefully take in more of that liquid so it wasn't froze solid. If you have a really wet, saturated soil and you freeze it, the pore space essentially goes to zero, right? It was all filled with water. If it was drained and has some pore space left, we can get some of that water, or manure water to infiltrate in. So drainage can be helpful there. If you have surface inlets, to take some of the drainage from those ponded areas, if you're doing any winter manure application, definitely sleeve that surface inlet, put a five gallon bucket around it, so that anything that does run towards it has time to soak into the soil and doesn't go to that, leave it covered for about two weeks. If you want, you can leave it covered a little longer especially that firstsnow melt or small rainfall event you have, you want to be protecting and getting that to soak into the ground. The next events after you've had that one that sort of soaked in isn't as risky, because we've moved that manure into contact with the soil where it'll hopefully where it'll hopefully stick, and the nutrients especially love to stick to soil. that's going to end up at a saturated buffer or bioreactor kind of situation? I think those are great questions, and it depends. Certainly, many of those nutrient practices make a lot of sense, and hopefully, though, in this case, we don't want our manure, especially right after putting it in contact with the soil, making it down to the tile line and moving with it. So when you think about what's in manure, we have ammonia. Or ammonia, depending on sort of the pH and conditions, we have phosphorus. Those love to stick to soil. When you think about saturated buffers, when you think about bioreactors, they're really there to treat nitrate. And during the winter, we know that microbial activity slows. It's proportional to temperature. So the winter conditions are going to limit how much of. That ammonia gets to turn into nitrate. How much of that nitrate moves down to the tile line until the next spring? So those are really water quality practices for nitrate. They aren't going to help us a whole lot with manure that would make it to the drainage system. Now the good news is, manure, those things, love to stick to soil, isn't probably going to make it to the drainage system. vegetative strips around the edge of your field, vegetative buffers, barriers, terraces, that help prevent some of that water moving as quickly, and definitely things that help to prevent some of erosion. So maybe having a cover crop around the edge of your field, the cover crop might hold a little snow for us.

Luke Soko:

Okay.

Dan Andersen:

But, and that's bad, right? As we talked about, we don't want that snow. But if you used a field and had that vegetative cover crop on the edge of the field, when we have runoff from the first rainfall event after we've done this, hopefully that vegetation will help catch some of those solid particles that are in the manure before they leave the field. So that's really what we're thinking about in this case, though, is more those surface runoff practices, and how do we prevent movement of that, rather than something that's attached to a drainage where it might be more focused on nitrate?

Luke Soko:

Yeah. Okay, well, that's interesting. So what about do all of these rules also apply to solid manure?

Dan Andersen:

So no, the rules in Iowa were only written for liquid manure because the higher risk that we've seen there. With so with solidd manure, it's just the best management practice not to apply manure. Now, there's certainly some cases where we might want to apply manure, solid manure in the winter, if you have an open feed lot and you're scraping some of those manure solids off to try and keep the pen condition in better condition for cattle production, we have to do something with them, and you might have a stockpiling pad. And if you do, great. We'd love to see you use that stockpiling pad if you don't. Sometimes it's the best management practice is to apply some of that solid manure in the winter so that we're not accumulating it, so that it's not all in one spot, if we get that wash in the summer, where it might move right, and putting it in the cattle pen. Leaving it in the cattle pen probably isn't a good option. The other thing we see with solid manure is with liquid manure, if we have compaction concerns, we often see people switching towards drag line application systems so they don't have those large tanks and well, unfortunately, we haven't invented a solidd manure dragline application system yet. It's sticky the salad manure and it's hard to move through a line, right? We'd have to use air and blow it, that just hasn't been very practical on anyone who's tried it for research. So we're normally left with large manure application equipment, relatively heavy. We'll probably dump a stockpile in a field, re-pick up from that, and that can cause some compaction. So sometimes they like to apply once the soil is frozen, because it helps minimize some of that compaction concern. Now the good news is, we've seen all the data suggest that there's less risk of nutrient movement with solid manure, it doesn't have that water with it to start with, it tends to melt more slowly and work through any snow that we have. Not always the case. It depends a little bit on the weather, so we still have to be thoughtful. But there isn't a regulation that prohibits that solid manure application. But we really want to be thinking about what are the field can thinking about, what are the field conditions? Is this the best I can do? Is this right for the field, the situation and the environment?

Luke Soko:

Okay. So would you recommend to farmers that you know, go out and check your manure storage in November and make sure that, I mean, because you said, you know, best practice early winter, if you have to.

Dan Andersen:

So that's definitely a balance. Now we're all trying to get our manure application done in the fall.

Luke Soko:

Yeah, yeah.

Dan Andersen:

And we want 50 degrees in cooling for especially many of our liquid manures that are high in ammonium and you're trying to sort of balance, Can I wait long enough? Can I get an applicator to come before I'm going to have that frozen or snow covered ground? So it is a balance. But certainly our manure storage should be getting low or emptied out in the winter, and that helps minimize some of that risk of needing to apply. Do you have a water line break, some other condition that really makes it almost an act outside of your control, where you have to do some of that solid manure? Yeah, if I'm sitting there and looking and say, either this barn is too full, I had a water line break. If I'm a four barn site, can I put some of that manure into the other barns rather than thinking about a manure storage? I know moving manure around from barn to barn is a hassle. There's biosecurity risks with doing it. It's just work without any potential gain. We have to handle it twice, but that's still the preferred what we'd want to see happen. If you are going to have a struggle, and you know that your pits too full on all your barns for whatever reason, then absolutely. If you're you're in that situation, think about how much do I need to remove to make it to my next application window in the spring, and you have to talk to the DNR. Have a plan, a field in your plan that's written as your emergency manure application field, unless you why this is happening and some detail about it to try and minimize the risk, and try and advise you on what are the best things you can do to help protect water quality. But definitely early is better. So if you know you have a problem, don't be waiting until the problem's imminent. Start planning ahead about what you need to do, and talk to either extension or DNR to get some advice on really, how do you work through that?

Luke Soko:

Okay, yeah. And especially, I mean, you were mentioning manure freezing about 26 degrees Fahrenheit. That is not that cold in Iowa.

Dan Andersen:

No, but a couple things on that, lakes don't lakes don't freeze solid, manure storages won't freeze out the freezing the top down. If you're in a deep pit situation, they're heated, right? We're not,

Luke Soko:

Yeah.

Dan Andersen:

so we're not freezing deep pit swine manure. Beef cattle deep pits you're going to see that top freeze, but then that ice really acts as an insulated barrier. So we're not freezing the manure solid in most of these cases, right? It's just the top portion that's gonna freeze.

Luke Soko:

Okay. What kind of resources exist specifically for winter manure application?

Dan Andersen:

So you can see in the show notes for this podcast that we have a couple flow charts to work through. One is, when does winter manure application rules and regulations apply to your farm. So it'll talk you through the basics of, is it a solid manure, is it a liquid manure? And then what are the key dates and land conditions that are important? So that's one resource understanding what's happening there. The second one is we have a second flow chart that really is working through the process. If you have to do an emergency application in the fall, who do you need to contact? What are you looking for? And what field conditions are should we be paying most attention to in terms of what are going to be most successful for us? And those are the two things I recommend. After that, it's really sort of the common sense things that we've talked about. How much snow is out there. Do I have a field that has less snow than other fields? Do I have a field that has less risk of phosphorus movement? So you're going to need a field in your manure plan that has a phosphorus index of less than two and is written as your emergency manure application field. If you think about solid manure, I'm really thinking the same things. How much snow cover is there? Am I better off to make sure I get it done today? Or am I better off? Am I going to have better weather conditions in a week or two? Right? And sometimes we know, and sometimes we're guessing based on the weather forecast experience, to say I'm better off waiting until that storm passes or or pushing through. And those are tough decisions, because the weather is a little bit unpredictable. But generally we see some time periods in the winter that probably are okay for winter manure application of solid manure and some that we probably should be trying to avoid. So thinking about which of those two are and how that relates to our fields, right? How much snow cover do we have? What's happened in that field? How wet has it been? What's the risks associated with that? And those are really personal field decisions that you get to go out and look at the field and make your assessment of, given the conditions I have, where I think the year is going. Is that the best choice I can make?

Luke Soko:

That sounds fantastic.

Dan Andersen:

All right, so a few key takeaways for us today. Certainly know the regulations, either in Iowa or your state as applicable. The law is really important on this subject. We want to make sure everyone stays in compliance. The second thing is, we talked about planning ahead, making sure that, where possible, we're trying to minimize or eliminate the amount of winter manure application we have to do, while, in some cases it may be necessary, we know that it is riskier than other seasons. So risk doesn't mean we're going to get that nutrient movement, but it does mean we have an elevated chance of causing that negative impact on water quality that we want to avoid. And then the third thing is really making sure that we're picking both our field and time as best we can, given the year the weather conditions and what we see happening with our farm operation and with the weather conditions moving forward. And there's no perfect on that, but we're really looking for fields that are as flat as possible to try and minimize the risk of surface over land flow moving rapidly, trying to avoid places where we have ponding, so leaving maybe some areas of the field that we don't hit if we have those areas that typically pond, making sure that we're sleeving surface intake, so that if we do have some runoff water, it doesn't make it down to the tile line and then increasing setback distances, so staying further away from key water features. Certainly, we love fields with residue on them or cover crops on them, but they can be prone to holding more of that snow. So in the situations where we have to do this emergency application or have to do this winter application and it's snowy, those fields might be less preferred. Now, if the snow is gone, those fields become more preferred, right? They're the ones we want, want to be getting to getting that manure in contact with the soil, because we know that soil loves to hold on to many of those manure nutrients and will help hold it there for the next growing season. So that thanks for joining me today, Luke.

Luke Soko:

Absolutely. Thank you.

Dan Andersen:

And thank you to all of you. And thank you to all of you for listening to some of our solid manure information relative to Iowa, and hopefully best tips that apply to other states as well. Thank you for joining this installment of Talkin' Crap. Be sure to take a look at the show notes on our website for links and materials mentioned in the episode. For more information or to get in touch, go to our website, www.extension.iastate.edu/immag/. If you found what you heard today useful or it made you think, we hope you subscribe to the show on your podcast app of choice. Signing off from a job that sometimes smells but never stinks, keep on talking crap you.