What's up with manure foaming? Where are we at with understanding the causes of foam formation on deep pit manure storages

Spontaneous foaming in swine manure pits is an ongoing challenge and has serious potential danger. Methane gas is trapped in the bubbles and creates the potential for fires and explosions, especially when the foam bubbles are rapidly destroyed and a spark occurs. Conditions that are especially dangerous are during agitation, pumping, or pressure washing or activities like welding and hot work where slag might fall into the foam. If you are dealing with foam make sure you take the appropriate precautions to ensure safety for you, your employees, and your pigs. Below are a few best tips for working with foam, or check out this video for a refresher on dealing with foam.

·         Provide continuous ventilation to prevent gas build-up. Increase ventilation during agitation to quickly dissipate released gases.

·         Turn off heater pilot light and other non-ventilation electrical systems, such as the feeding system), that might produce an ignition spark.

·         When pumping pits that are close to being full, pump without agitation until manure is about 2 ft. below the slats.

Research

Over the last three years, a collaborative research project to understand and mitigate the causes of foam has been conducted by Iowa State University, the University of Minnesota, and the University of Illinois. A lot of information has been learned about foam and its potential causes, and that information is briefly shared below.

Gas Production

Methane is always produced during anaerobic breakdown of manure, so when we store manure in a deep pit, we are going to generate methane. However, it was determined foaming barns are consistently producing methane at faster rates than their non-foaming counterparts, often producing 2-3 times as much methane per day. This led researchers to start asking why this might be happening. Through several dietary feeding trials, it was discovered that diets higher in fiber tend to be less digested by the pig, which results in more carbon entering the manure storage. To microbes, this carbon is a food source, it’s the energy they need to grow and thrive. Researchers believe this shows recent dietary changes, like feeding more DDGS (a feedstuff high in fiber and protein) puts the fuel in the manure to build a more active microbial community. For example, a study by Dr. Brian Kerr, of USDA-ARS, tested how ration impacted the amount of carbon in the manure and found a diet with 35% DDGS inclusion resulted in 40% more carbon in the manure than pigs fed a corn-soybean meal based ration. However, just putting the energy in the manure doesn’t guarantee foam, a microbial community needs to develop that breaks it down quickly.

What’s this mean for mitigation? Finding ways to get lower methane production should lead to less foam. Items that reduce carbon in the manure lower the chance of foam by reducing the microbial food supply. This could dietary change towards more digestible feed ingredients (typically those lower in fiber content) or finding ways to make currently utilized ingredients more digestible (including finer grinding or feed treatments to improve digestion an incorporation in the pig). This also indicate that treatments, such as ionophores (Narasin or similar), that impact the methane production pathways can be effective treatments as they lower methane production rates.

Foam Stabilization

The second important part is the need for something to stabilize the bubbles to help a foam form. Research has found the stabilizing agent are fine sized particles (2-25 µm) that are enriched in proteins, but it takes something to bind those proteins together. What’s that something? At this point researchers aren’t 100% certain, but best data suggests it is a microbially produced poly-liposaccharide, aka microbial goo. This microbial goo causes the foam to be very viscous, keeping the bubbles wet and making them last longer.

One way of thinking about the chemistry of this stabilization is like comparing it to making meringue for your lemon meringue pie. In that case you take some egg whites (just the white, we want the proteins which have hydrophobic, or water hating, and hydrophilic, or water loving, areas) and then start whipping it to entrain air into it. This alone isn’t enough though; something needs to stabilize the meringue. That’s where sugar comes in. Slowly add sugar and keep whipping and you’ll end up with a tasty meringue that’s light and fluffy and will persist for a long time. The sugars bond with the proteins and hold it all together.

What’s happening in the manure is surprisingly similar, the biogas moving through the manure brings those bits of protein to the surface (just like when we separate the whites from the yolk to make meringue), it also churns them up and causes them to orientate themselves so their hydrophobic areas are towards the bubble and the hydrophilic areas to the manure. When they react with some of that microbial poly-liposaccharide, stabilized foam results.

What’s this mean for foam mitigation? This tells us there are two parts we can focus on to destabilize the foam, the protein or the microbial poly-liposaccharide. Research has shown that treatments that destabilize the proteins, such as proteases, can greatly reduce foaming capacity and foaming stability. Other treatments that seed microbes, especially microbes known to produce proteases, into the manure may be a viable treatment and are being tested both at the laboratory-scale and in-the-barn. As proteins are an important component of the stabilized foam, diets that lead to more protein excretion (typically higher protein contents) would seem to have greater potential for foam formation. A swine feeding trial focused how different levels of protein and sources of protein impacted manure foaming properties. The results of this trial showed that higher protein diets led to manures that had higher foaming capacity, greater foam stability, and higher methane production rates – all characteristics of foaming manures.

The second component that could be targeted as a mitigation approach is the microibally produced poly-liposaccharide. Efforts to extract and better characterize this substance are underway; however, at this time not enough is known about material, or the microbe that produces it, to target this specific aspect of foaming.

Microbes

How does all of this explain when you have two barns that are treated the same; same pigs, same diets, they are as similar as they can be, but one foams and one doesn’t? It’s all about the microbial community that develops in the manure. Certainly the dietary ingredients can influence microbial community, but other factors seem to make as much of a difference. This was true both in the field and with the feeding trials that were conducted; however, based on the feeding trials it was clear that certain properties did influence the microbial community that developed. In particular, our study showed that manure carbon contents (microbial food) led to differences in microbial. Our evidence suggests that in the field higher fiber diets, especially from DDGS, tended to lead to foaming communities for to crusting.

In the case of non-foaming manures, the microbial community tended to be focused on lactobacillus and VFA processing. Within these barns the manures showed an accumulation of volatile fatty acids, which lead to slightly lower surface tension in the manure, and lower methane production rates. Foaming manures exhibited microbial communities that were slightly correlated to higher added oil in the diets and exhibited increased presence of ruminococcaceae, ruminococus, and bateroidales and had a higher portion of the microbial community from unclassified methanogens, which seemed to be correlated to the higher methane production rates.

In terms of mitigation we are currently working to better correlate why these microbes become more prevalent as well as methods to alter and modify the microbial community. In particular, we initiated a study to evaluate if increasing lactobacillus in the manure can alter the amount of volatile fatty acids in the manure and upset the unclassified methanogens in the manure to alleviate foaming.

Leon’s Safety Message:

September 15^th, 2014…. This past year Leon Sheets shared the story, his story, of a fire/explosion at his swine barn. His important message reminds us all the importance of safety. “Farmers need to be careful whether they are pumping, power washing, or doing maintenance, when it comes to these accidents, we want no more, nobody else.” Take the time to hear Leon’s message.

Are you taking your safety seriously when dealing with manure?

Hydrogen sulfide gas and foaming continue to be a serious issue in and around barns. But don't take my word for it. Hear Leon Sheet tell about what happened to him and why you need to take this issue seriously. Your safety is important to us and we are always humbled to hear our messages makes a difference. Hear Kris Kohl talk about his recent experience when a farmer told him about remembering hearing about hydrogen sulfide in training and how to react. We all on the manure team here at Iowa State feel the same way, and hope you take the time to educate yourself about ways to keep yourself safe and check out some of the resources below for altering you of H2S dangers.

Hydrogen sulfide is especially concerning when agitating or pumping the manure. As the amount of distiller’s grains in feed rations has increased, so has the amount of sulfur excreted by the animal. Over the past ten years, sulfur concentrations in swine manure have increased from 3 pounds per 1000 gallons to 9 pounds per 1000 gallons. When manure is agitated, hydrogen sulfide gas can be quickly released. Exposure to low concentrations of the gas for even a short period of time can cause health issues and at high enough concentrations can cause near instant death. A list of symptoms to different hydrogen sulfide exposures is provided in Table 1.

If you work around manure, monitors can be purchased to help keep you and your employees safe. A monitor, which is small enough to wear, ranges in cost from $99-$800 and will alert you if the situation is dangerous. This year as part of the manure applicators program participants were asked if they currently use any type of hydrogen sulfide monitoring equipment. On the commercial applicators survey, 5 percent of workers reported using a hydrogen sulfide monitor compared to 1 percent of confinement applicators survey. When asked about the likelihood of purchasing a monitor, 25 percent of commercial applicators and 31 percent of confinement applicators said it was likely that they would purchase a monitor (for a summary of this information see Figures 1 a and b below).

There are numerous options available for monitoring hydrogen sulfide levels when working with manure. Below are links to four meters for you to take a look at and some pictures of what they look like.

1. Honeywell GasAlertMax XT II
2. BW Honeywell GasAlert Clip Extreme GA24XT-H
3. BW Honeywell GasAlert Micro Clip XL 4-Gas Monitor
4. Draeger Pac 3500 H2S Monitor
5. RAE Systems ToxiRAE II

In addition to considering purchasing a monitor, other practices to follow when agitating or pumping manure include:

• Check to ensure all ventilation fans are working prior to pumping and that air inlets are open
• Place a tarp over pump-out to help protect the applicator
• Communicate with farmer and crew and never enter a barn during agitation and pumping
• Listen for pig distress
• Always be aware and alert as dangerous situations can develop quickly.

What does manure application cost?

What's it going to cost me? This seems to be a popular question these days, whether it be someone looking to compare different application systems (like tanks to umbilical systems) or just trying to figure out the value manure might have in their farming operation, determining costs are critical to developing the best manure plan for your farm. I won’t pretend to have all the answers, but what I do have is some data from 41 commercial manure application business provided us in the Fall of 2013 in response to a survey (three long years ago already so it might be time to start thinking about updating that) and a quick and dirty cost estimation technique.

So a few years back we asked commercial manure applicators in Iowa what they were charging to apply liquid manure (it could have been with an umbilical system, it could be with tanks I didn't ask what method they were using) and how that price varied with some different hauling distance. We have 41 business reply with responses (my best guess is there are around 550 commercial manure application businesses in Iowa, at least that is how many are currently certified). Fewer companies did give responses for the further distances - our response rate was: 1 mile, 41 responses; 1-3 miles, 38 responses; 3-5 miles, 25 responses; 5-10 miles, 11 responses, and greater than 10 miles, 4 responses). Within each distance category I calculated the average application price and standard deviation of the price.

The results indicated that at one mile the average price was $0.013 per gallon of manure applied. A regression equation fit the data well indicating that the manure application cost was about $0.01 per gallon and indicate that there would be a cost of about $0.0035 per gallon per mile the manure is hauled. Although this pattern generally held true there was greater variability in price at greater transport distances. A few comments, remember, these are approximate prices, actual price is also dependent on farm characteristics (application rate, travel path to the field, etc.), as well as the hauling equipment used.

Figure 1. Estimated manure application cost as a function of transport distance. Error bars represent the standard deviation in reported price.

An important question we can ask is what should we expect the relationship between hauling distance and cost look like? Another way of answering this question is to perform a 1^st order estimate of costs. I take a bit of time and came up with some of my best estimates of what it would cost. Scouring on-line I found a 5250-gallon manure tank for sale for $40,000 that I estimated I could get 5-years of use from, giving an annual investment (assuming 4% interest) of $8985. Assuming I’m applying about 1.5 million gallons a year (right around 300 spreader loads) this would be somewhere around $0.006 per gallon of manure in capital expense. The next step is to estimate some operating expenses. In this case I’m going to estimate about $50 an hour for fuel and lubricant costs for the tractor and $15 an hour in labor costs. The better you can estimate these numbers, the more accurate your price estimate will be.

I then went about figuring out how different hauling distances would change my productivity, i.e., the flow rate I could achieve with this tanker at different hauling distances. To get an estimate of operating costs I assumed it would be 4 minutes to position the spreader at the loading platform, 8 minutes for loading, and 8 minutes to unload in the field. Travel time to and from the field accounts for the remaining time; to calculate travel time I assumed a speed of 8 minutes per mile. If you use these assumptions and plot the cost of manure application as a function of transport distance you get a roughly the cost function that we found empirically from our survey. Again note, that these estimates of loading, travel, and emptying time can have a big input on cost; the number I chose are a good first estimate but should be tailored to your equipment for a better estimate.

Figure 2. Calculated manure application cost as a function of transport distance based on the above example.

Beef Manure Management Systems - Manure Quality

Manure quality is dependent upon management practices and the manure handling system. Though we can adjust an animal’s diet through practices like phase feeding or supplementing specific amino acids, generally only 10-20% of the nitrogen and phosphorus fed to an animal is retained by the animal. The majority of the nutrients are excreted in the manure. Depending on the type of finishing site and your goals as a producer, there are different ways to evaluate manure quality.

At finishing sites, manure handling systems can be separated into 3 types: open lots (concrete lot and earthen lot), deep pit confinement barns, and bedded confinement facilities (hoop barns and monoslopes). While we start with roughly the same amount of nutrients in the manure of the animal, the way the manure is stored, treated, and handled can lead to drastically different nutrient contents. For example, though open lots and bedded confinement facilities both have solid manure, the amount of bedding used in each facility varies greatly. More bedding is used in a confinement facility to absorb liquids than in an open lot.

Beef finishing cattle on a fresh bed pack. Photo credit:  Rachel Klein, Ag & Natural Resources, ISUEO 

Another consideration is that nutrients can be lost between the time the manure is excreted and it is land applied. In the case of nitrogen, in an open lot, 50-70% of excreted nitrogen can be volatilized, or lost as a gas, while it sits between cleanings. In a bedded confinement urine is soaked up quickly with the bedding, reducing nitrogen volatilization to around 30%. In a deep pit barn since the manure is a liquid, it is easier for the free ammonia to be volatilized. However, since the manure in these storages have small surface area, losses of 15-30% of excreted nitrogen can be expected.

The amount of manure generated by each system varies as well. In general, an open lot typically generates 3.5 tons of manure per cattle per space. However, this number varies greatly due to weather conditions, management practices, site locations, and the moisture content of the manure when scraped. A deep pit systems averages about 6.5 gallons per head per day or about 10 tons of manure per space.  In a bedded confinement, around 6 tons of manure produced each year, assuming it is around 30% dry matter for bedding use.

The summary table below provides an idea of how much of the nutrients are retained in the different manure handling systems.  Deep pits have the advantage, as they hold onto more of the nutrients, but bedded confinements closely follow with the amount of nutrients retained. 

Facility Type	Total N Lbs/space-year	P2O5 Lbs/space-year	K2O Lbs/space-year
Open Lot (runoff not included)	66	48	54
Bedded confinement	98	57	58
Deep pit	94	59	82
Excreted	122	68	93

Which system you select is also dependent on your application goals. If you are moving manures a long ways, solid manures might be better because they are more nutrient dense, but sometimes liquid manure systems are nice because they are easier to automate.

Beef finishing cattle on an open lot. Photo credit:  Rachel Klein, Ag & Natural Resources, ISUEO 

Sand settling lanes and Stokes' law -

A few weeks ago I made it home to my parent’s farm. While I was there I jumped at the chance to tour the dairy next door. The dairy is still relatively new and one of the biggest in the area I grew up in. Sure I was excited to see the freestall barns, the parlor, and their recording system for cow health and milk production, but let’s be honest, I was there to see the manure handling system (well that and my family).

So as I get started a big thanks to the dairy for the chance to walk around on a Saturday morning and hear what was going on at your farm. A few facts to get us started. The farm currently has around 2,400 cows and uses a GEA double 35 parlor (growing up we milked about 30 cows so yeah, we could almost fill half the parlor!). Like lots of dairies, this one chose to use sand. Sand can be a clean, comfortable bedding that can promotes conditions for low bacteria counts for mastitis control.
I wrote an earlier post , Can application of sand laden manure impact soil texture?, (available at http://themanurescoop.blogspot.com/2015/08/can-application-of-sand-laden-manure.html), and as I discussed there one of the best ways of avoiding that issue of land applying sand is a good sand recovery system. So, that is the topic for today. In particular, I thought I’d talk and show some sand settling lanes since that is what this farm was using.

There is a lot you can talk about when it comes to sand settling lanes and I won’t cover it all here, just a few pictures and a little science. So I’ll start with the picture. What is a sand settling lane? Well just like the name makes it sound, it’s a lane (think land like a bowling alley lane) where we want sand being carried in our water-manure-sand mixture to settle out. By settle out, I mean the sand hits the bottom and is says in the lane where it can later be scooped out. The sand that is scooped out is then laid out in windrows and turned a few times to facilitate drying of the sand. These steps are shown in the photos below.

Photo 1. Sand settling lane.

Photo 2. Stockpiled sand

To be successful and make good sand bedding, we want to recover as much of the sand as possible, but not the organic matter in the manure; that is we want to make clean sand.
Now to the science of the settling lane. The idea is to use gravity and density differences to drive the separation. Stokes’ law is often used to describe this, as shown in equation 1.
V=((ρp-ρw )/18μ)*gD^2

Where V is the rate settling velocity of a particle (m/s), ρp and ρw are the densities of the particle and the density of water respectively (kg/m3), µ is the viscosity of the fluid (kg/m-s), g is the gravitational acceleration constant (m/s2), D is the diameter of the particle (m).
Looking at this equation there are a few things you can quickly take away from it. In particular, there are two parameters, the particle density and the particle radius, that influence how quickly particles will settle. It says that big particles settle more quickly and that denser particles settle more quickly. To have effective separation of sand and organic matter what we need is to have a big enough difference in the rate that the organic matter in the manure and the sand in the manure settle so that we only capture the sand.

So, what do we know about the characteristics of sand and manure particles. Almost all sands have particle densities of right around 2650 kg/m3, but the particle size can vary depending on the type of sand you purchase, but typically will have a particle size of around 0.25 mm or so. If you plug both of these into Stokes’ law you get a settling velocity of around 1 m/s.

If we contrast with manure solids the particle density if closer to 1500 kg/m3 (though it does vary with the amount of fixed and volatile solids in the manure (see figure below, note that fixed solids are mineral solids and volatile solids would be organic matter) and dairy manure solids have a geometric mean diameter of around 0.17 mm. If you plug these values into Stokes’ law you get a settling velocity of 0.14 m/s! That is much slower than what we got for the sand particles. As a matter of fact, a dairy manure solid particle could be 0.5 mm in size (which about 70% of all dairy manure solid particles are smaller than) and still only settle as fast a sand particle that was 0.25 mm because the particle itself is so much less dense than the sand particle.

Although it may sound simple, designing and managing the settling land so we are capturing as much of the sand but as little of the organic manure solids can sometimes be a real challenge. So next time you have a glass of milk, sit back and think about all the work, effort, and science that keeps those farms running. I know I will, and maybe I’ll even be tinkering with Stoke’s law trying to think about how changes in season, changes in type of sand used, or how flow, stope and size come together to make a sand settling lane possible.

Are you listening to your manure storage?

Are you paying attention to what your storage is telling you? Although we have traditionally done most of our manure application in the fall, spring application is becoming more common. There is a variety of reasons for this, ranging from striving from better nutrient management, to labor availability, available application days in the fall, and just general storage management.

This past fall, field conditions were difficult for getting manure application finished in some parts of the state, it got rainy and stayed wet – not exactly great manure application conditions. Add to that that harvest was a bit delayed this year (which means we had lots of manure to get applied and fewer days than normal to get it all done), and we have a recipe for some fuller storages this spring. (That’s not even mentioning that soils cooled to 50-degrees later than normal and once they did they quickly dropped to freezing temperatures). Put all this together and it seems like we should be asking looking at if we have enough manure storage to make it to the fall or if we should be looking at applying some of our manure this spring while our fields are open.

 

It goes without saying, but one of the most important aspects of being a good environmental steward is managing your manure storage so that it doesn’t overflow. I talk and write often about the right place, right time, right method approach to nutrient management, and these concepts are important, but all the good they do can be quickly washed away if we aren’t managing our storage to prevent overflows from occurring. So what should you be looking at in your storage right now?

You should be assessing how much storage you have left available compared to the amount of manure you anticipate generating until your next application window.  Right now we are looking at somewhere around 6.5 to 7 months (26-28 weeks) until we reach our fall application window. As a rough rule of thumb I’m expecting about 1 to 1.25 inches of manure accumulation in a deep-pit swine finishing barn every week, this means that you are looking at about three feet of manure between now and early October. If you plan on making it until your soils have cooled in the fall, and you will probably be looking at closer to 3.5 feet of manure. Do you have that sort of storage space left? If not, think about using spring as a chance to do a little insurance hauling this spring to make sure we are putting our manure resources to good use now and can pick the best times in the fall too.

Unfortunately, I don’t have numbers like that for different animal species at the tips of my fingers (for lots of reasons, one being that if you build an outside storage you need to account for rainfall, but also can have different shapes to your storage), but hopefully you do. Installing a staff gauge in your manure storage (or having a way that you can accurately estimate how full the storage is) is a great way to compare year-to-year and make sure things are where you’d expect. It can also be useful for detecting a water leak, deterring if outside runoff water is entering your storage or something else funny is happening if you are not filling up at the rate you expected.

Winter Manure Application - The rules and a few other thoughts

This year I've been getting quite a few questions on winter manure application, some from farmers, some from the general public, and some from people who saw some manure being applied as they drove by on the road who wondered what my thoughts were on the topic or what the science says about these practices.

So let's start with the law. Many of you have probably heard that Iowa does have a snow covered and frozen ground rule, but are you aware of what it says and who it applies to? Iowa code placed a restriction on application of liquid and slurry manure's from confinement animal feeding operations (basically means animals raised under a roof) with more than 500 animal units. These rules also have effective date ranges, for example it says if the ground is snow-covered between Dec. 21 and April 1 then liquid manure from these operations can't be applied (unless we could inject it or perform an incorporation on the day of application or they had a manure emergency). For completeness the dates on frozen ground portion of the rule run from Feb. 1 to April 1.

So say its January 3rd and there is no snow on the ground could these operations legally apply manure? Yes. However, if its February 3rd, there is now snow on the ground but the ground is frozen can these operations legally apply manure? No. Some of you may be thinking, why those particular dates - why not just just say snow covered fields? Well, a few reasons actually - some science based and some practically based. First the science reasons. What the research has shown is that the amount of nutrient we lose after a manure application depends on lots of factors, but some of the most important are the size of the runoff event and the amount of time after manure application before the runoff event occurs. This means that I worry more about nutrient loss from manure that gets applied closer to spring melt than manures that get surface applied in the fall that get some reaction time with the soil. The other thing to remember is these dates weren't just arbitrarily selected, they were researched in relation to typical soil temperatures, snowfall chances, and runoff risk.

Along with that there are some practical reasons. Giving dates provides some certainty to the rule and lets us plan accordingly. One of the things you might have seen me talk about before (or write about on here) is try to wait until soil temperatures are 50-degrees and cooling before you apply manure (especially ammonium rich manures, like most swine manures) in the fall. This recommendation is based on trying to keep nitrogen in the ammonium form rather than getting it converted to nitrate in the soil - things that matter in this process are time and temperature and the 50-degree recommendation seems pretty appropriate for most of Iowa. However, following this recommendation might mean waiting until mid to late November. What if we get that early snow storm or a soil freeze quickly after that and didn't get our manure application completed? Well, that would certainly put us in a bind and realizing that risk existed we might be more anxious about getting my manure applied in the fall, and as a result choose to apply it earlier to mitigate the risk of getting stuck with a full storage. So essentially what we are really trying to do is balance the risk of two competing recommendations, that is delaying manure application until soils cool but not putting it on frozen ground. Effective dates provide at least a little certainty in this equation - hence I'm a big fan of dates as I feel it puts us in a better position to make the most appropriate decisions.

There are two other things I want you to note about the rule; there is a farm size threshold (500 animal units) before it applies to you. Why is this in there? Again I'd suggest its about risk. In this case the number of acres that would be impacted and the resulting effect that could have on water quality. More manure might mean more impact, since more acres are impacted. Does this mean if you are below this threshold go right ahead and apply manure all winter long? No, we certainly want them to minimize winter application as well especially during riskier times such as during snow melt, but again manure decisions at these farms are a balancing of competing factors - how much it costs to build a larger storage, how long they will continue to farm, and the the economics of animal production. 

The other thing to note is that the rule was written to apply to liquid and slurry manure, it does not include solid manure. In some ways this probably makes some sense - if we poor a glass of water on frozen or snow covered soil does it soak in and is it held by the soil? It probably depends to at least some level how wet the soil was when it froze, but we can probably see the risk of it flowing away. With solid manure there isn't this direct runoff concern at the time of application; instead we worry about liquid (rainfall or snow melt that will pick up and move those nutrients). We'd certainly recognize there are a least some differences in risk between solid and liquid manures. Again, that doesn't mean we should be out there applying all winter long - but there are some logistic constraints (only so many days int he fall especially with a late harvest) on manure application that come into play. However, if we are out there in the winter we need to focus on doing what we can to protect water - that means picking the right fields, the right weather conditions, and making sure our equipment and decisions are specific to that environment.

So if the snow covered and winter manure application rule don't apply to your farm are there any regulations that do apply? Yes! There is a Iowa DNR fact sheet that lists "Separation distance for land application of manures from open feedlots and confinement feeding operations of all sizes." (If you need a copy let me know and I'll get you one). This fact sheet says a setback - no application area - of at least 200 feet is required from a sinkhole, abandoned well, drinking water well, designated wetland, or water source (any sort of stream) if manure is surface applied and not incorporated (that applies to both solid and liquid manures) [800 feet if the water is listed as a high quality water resource]. Alternatively, you can maintain a permanent grass buffer between the manure application area (at least 50 feet wide) and those designated area to meet this requirement. No manure in the buffer!

Alright, so we've covered the rules and you still want to apply in the winter what's next. Stop and think about it for one more minute? Okay, perhaps we find ourselves in a situation where we have to apply (maybe its logistic, maybe its a storage emergency, maybe its another reason I missed), but we need to ask is this the best decision we can make based on all the other factors impacting our manure management decision.  If yes, its time to really think about water quality and what we are going to do to limit the risk of any winter manure application. It needs to start with identifying the best fields for this choice - look for level ground and places where you have soil erosion controlled. Beyond that its timing and weather - these two factors tend to be the largest drivers of nutrient loss. This means watching the weather forecast and avoiding application before anticipated rainfall and snowmelts.

Additional recommendations include incorporating the manure when you can, avoiding areas of concentrated flow such as waterways, ditches, or similar areas,  using setbacks from sensitive areas like stream banks, sinkholes, and similar, and if possible avoiding application near areas that drain to surface tile inlets. If these areas can’t be avoided add protection around drainage tile intakes to prevent entry by manure or runoff water.

If winter manure applications are not avoidable,

• Take into account soil and weather conditions
• Avoid applying before a snowmelt or rainfall event
• Apply to areas of level ground and where soil erosion is controlled
• Apply to areas with less snow cover
• Follow appropriate setback distances
• Update your Manure Management plan to reflect surface application rates and if subject to Master Matrix requirements for injection or incorporation get approval before surface applying