Thursday, April 17, 2008

Mow, Bale, or Burn?

About a month ago I wrote a little bit about our pasture on the farm. Right now the entire 26 acres of pasture is in the Conservation Reserve Program and it appears to have been seeded into switchgrass at some point during its tenure in CRP. The switchgrass is a nice warm season grass that we hope to maintain as part of the pastures (it will be difficult), but judging by the amount of small trees and brush growing it has been awhile since it was last burned off or mowed. So, the grass is really tall and not really ready for grazing by our Dexters. Which leads us to the question at hand ... Mow, Bale, or Burn?

The picture above (click image for larger picture) shows some of the grass still standing and some of the area that we mowed on Tuesday. My dad test drives County Clipper ZTR mowers so I had him bring one up and we mowed the area around the building site so we could more easily envision the project and to see what it looks like after a couple of passes with a mower. Of course there is a lot of residue on the ground after mowing, but it is fairly well chopped up. One thing that I did notice after mowing was that there are there are clumps of switchgrass and then there are spots were other grasses are coming on. We are supposed to get some rain tomorrow and then a slight warm up on the weekend, so we will see if the grass pops.

I'm not sure if the residue from chopping up the grass is too much cover for new grass to come through or if it is just really good organic matter that can be incorporated into the soil. That is why I have been thinking about the second option, baling. I could go out and mow and rake the grass and then have a friend come in and bale it up to get it off of the ground. The bales would be much good for feed, but they could be used for composting or something. The main reason behind this is to open up the growing grass to more sunlight, but maybe the mowed grass residue would help keep moisture in?

The final option is to burn it off. Maybe this would be the most natural way to manage a pasture full of native switchgrass, but I'm just sure that I have the patience. Right now there are plenty of wet spots around the farm because of all of the rain, and judging by the forecast they will be wet for a while longer! Also, there is a waiting list that we are on to have the Rural Fire Department do the burn and it could be a while before they get to us. I think I just may cross this option off of the list unless I come up with some compelling evidence to make me patiently wait.

What are your thoughts?


Steven said...

If you planned on doing any deep bedding in a barn, baling some would be nice but if the switchgrass is anything like bermuda now.... the cattle wont touch it.

Rich said...

How about all of the above?

I would at least bale part of it to test the haybine, rake, and baler you bought recently. Making repairs or minor adjustments is much easier (and less stressful) when your supply of winter hay isn't in jeopardy. The bales could be used as erosion control, as bedding, or in a deep bedding pigaerator structure.

Mow part of it. Mowing would leave residue on the ground, but isn't that what earthworms were created for? Think of it as earthworm habitat, the mulch will help create the conditions for a healthy earthworm population and they will incorporate the residue into the soil for you.

Burning part of your pasture will help control the brush, and will help create the conditions needed to establish some of the native grasses.

Don't forget that having a diverse farm operation also means having a diverse group of grasses in your pastures. Each of the ways of dealing with your pasture you are considering will have a slightly different result and will slowly create a more diverse forage base.

Andrew said...

What's your soil like? the easiest way to improve it and increase the carbon content would be to mow the grass and let it breakdown. As Rich said above, let the worms do the work.

As for burning, do you really want to let all that useful material just burn up into the sky, and leave the soil exposed to all the weed seeds in the neighbourhood?

I get that your farming practices may differ from organic ones, but that's what we do. No till, add as much material to increase soil carbon and let the worms and soil microbes do what they do best. It works well for us.

Rich said...

"As for burning, do you really want to let all that useful material just burn up into the sky..."

There is a place for burning in many cases, burning can be beneficial in many ways besides simply removing accumulated thatch and the remains of the previous years growth.

Several studies have documented a higher rate of gain in stockers grazing pastures that were burned right before greenup in the spring (Why do you think most of the the Flint Hills area of Kansas is burned every spring?). In addition to an improved forage growth, I personally think that a good portion of the benefit is due to a reduction in parasite populations, i.e. internal parasites like worms, and external parasites like ticks and hornflies.

Another reason in favor of burning is improving the soil itself. In the last few years, I have developed an interest in the charcoal rich Amazonian soils that are called Terra Preta, and been trying to recreate these soils in garden plots, etc. My attempts to recreate Terra Preta have focused on adding charcoal dust to the composting process and amending garden soil with the result (there definitely seems to be positive results). I think that if a controlled burn was planned to fall during a period of light rain, you could conceivably recreate the microscopic charcoal needed to recreate the Terra Preta soils over a larger area like a pasture.

Burning is a valuable management tool, but should be used properly (always safely) and at the right time to achieve the desired results.

Ethan Book said...

Steven - You are right, the Dexters wouldn't so much enjoy the switchgrass right now, so it needs to be cut down so we can get some nice new growth.

Rich - I'm with you on doing a little bit of each. The only one that I'm worried about is burning because we have had so much rain. I'm afraid by the time the rural fire department made it to us it would be the middle of the summer.

Andrew and Rich - I would say that we would be mainly organic. We will not be using any chemicals on the land. I do think that burning is useful in moderation, but I know that there is a wide range of opinions on the subject. We will probably end up mowing most of it though ... because it will be the easiest with a crazy schedule.

Jena said...

I was just talking with a colleague yesterday about pasture improvement and he has had excellent results spreading his cow manure very thickly on scrubby parts of his field. He puts the tractor in the lowest gear and the spreader in the highest gear so I would imagine it covers the existing grass quite a bit. After two years of doing this once per year he has lush pasture in an area that would only grow thorn apple trees before. I know that switchgrass wouldn't be as rich as the manure but I would think that if grass comes up nicely through that it would come up just as well through some clippings. I agree with the others that the earthworms should work their backs here, not you. Of course, it sounds like there are benefits either way you go. Good luck and congrats on the farm purchase - I'm sure you are very excited! :)

Ernie said...

Ethan, alot of Grass farmers around here do a 1/4 burn. They split their pasture into 1/4's and burn one 1/4 one year and another the next. It has been found to be benifical to cattle as well as wildlife. (Praire Chicken in Kansas)


Mellifera said...


Terra Preta rocks! I've been thinking that if we ever got a plot to garden on here we'd have to charcoal it up before anything would grow on it. (The dirt here is nothing but sand and won't even grow grass without serious help.... otherwise your lawn has male-pattern baldness).

The thing about Terra Preta that's got everybody flummoxed is it's not just ashes- like you said, it's charcoal. Charcoal happens from heating wood in the absence of oxygen (in some kind of airtight container with a heat source underneath), so you definitely don't get it from a normal slash-and-burn fire (or field burning)(at least, not very much). That's just ash, which is made of a lot of nutrients. Charcoal, on the other hand, is organic matter that got broken without enough oxygen to burn all the way into CO2 and just blow away in smoke. It's sort of like super-humus. It doesn't contain many nutrients per se, but like humus it has all kinds of little "pockets" that hang onto nutrients that are there. Otherwise in Amazonia they would wash right down through the dirt with the next rainfall, which is why slash-and-burn fields have to be abandoned after 2-3 crops. Unlike humus, charcoal doesn't break down very fast at room temperature, so it has staying power in tropical fast-rot conditions.

So yeah... they did the math and figured out that the area of Terra Preta soils in Brazil might be as big in area as France. And it takes a lot of work (and a LOT of wood) to make that much charcoal. So you start thinking, "Dadgumn! What were those Amazonians UP to?" Any figuring we can do on how much wood and how many centuries it must have taken boggle the mind.

Rich said...

"...And it takes a lot of work (and a LOT of wood) to make that much charcoal..."

Wood isn't required to make charcoal, it can be made with almost any organic material. Leaves, grass, animal bones, all could have been carbonized to make charcoal either by design or accident. Plus, earthworms would have helped incorporate the charcoal to the depths found in the Amazonian soils.

For almost three years, I've made my own version of Terra Petra by adding charcoal to compost, and applying it to the garden, once it is added to the soil there is an obvious difference to the soil. As an added bonus, the charcoal seems to absorb any offensive odors from the compost pile almost immediately after it is mixed into the pile. I suspect that the charcoal is absorbing the volatile gases, like ammonia (N), and slowly releasing them into the soil, acting as a storage unit to control excess nutrients until the soil needs it.

I encourage anyone to experiment with adding charcoal (natural lump charcoal not briquets) to their soils and compost piles.

While reading about Terra Petra, I also have been intrigued by the theory that the Amazon is not so much an untouched wilderness but a vast overgrown garden, created by the very same peoples that created the Terra Petra soils.

Mellifera said...

It's true, any organic matter can be made into charcoal. Let me also caveat by saying the last I really looked at Terra Preta was 4-5 years ago... they might have changed their minds about how it works since then. : )

As I understand it any process for making charcoal is pretty intensive- the material has to get hot enough to carbonize but can't have oxygen or it will oxidize all the way to CO2 and gas off. The wikipedia entry seems to talk about "slash-and-char," which sounds like just slash-and-burn at lower temperatures... but on the other hand there's still plenty of oxygen, so to get any appreciable amount of charcoal accumulated with an exposed fire you'd really have to go through a lot of biomass. In New England to make charcoal they'd make a big pile of wood, cover it with sod to seal the air out, and light fires on top for a week or two to heat the wood inside so as to get a decent percentage of the wood out as charcoal. Now what I want to know is who figured out the dirt+charcoal=bonanza equation! It might have been pretty obvious ("Wow, weeds sure seem to love old campfires even more than burned fields"), but if it was, you'd think people in other tropical areas would have invented it as well.

I remember somebody mentioning once that we should look at the avocado as a cherry for giant ground sloths. (Ain't nobody else swallows a seed like that.) So once the ground sloth went extinct, the avocado would have followed it pretty quickly unless there'd been people around to keep planting them. Pretty good argument for the Amazon-as-giant-orchard theory I think.

Rich said...

"'d think people in other tropical areas would have invented it as well..."

What makes you think they haven't? If nobody is looking for evidence of other soils manipulated by mankind they probably won't be found. The "experts" can't agree that Terra Petra soils are actually man-made, or that the charcoal has any effect on the fertility of the soils. Regardless of the projections of how much biomass would have been needed to produce the charcoal and the impossibility of producing that amount of charcoal, they can't escape the fact that it does exist, the charcoal was somehow produced. I don't understand why the "experts" in academia argue about whether or not it could have been done, because due to the evidence found in Terra Petra soils, it is obvious that it was done.

From the accounts of Terra Petra I've read, very few researchers have tried to explain how the clay pot fragments present in the soil were produced. Clay pots would have had to be fired in some sort of oven (which would probably have produced charcoal as a byproduct). Unless I'm mistaken most of the Terra Petra sites were also connected by a system of earthen causeways and canals. Canals imply the use of dugout canoes, which are made by charring out a log with small fires that repeatably lit and extinguished, with the charred material being scraped out to slowly form the shape of the canoe. After the effort put into the canals, a number of canoes would probably have been built to take advantage of the waterways, again producing a significant amount of charcoal (and pot shards used for scraping?).

The building of canoes is still a significant ritual in most "primitive" cultures that still exist today. I can see the connection being made with the sacredness of the building of the canoe, the clay pot kiln, and the garden that provides the community's food.

On a practical note, making charcoal can be as easy as getting a good fire going, feeding it with fuel until a good bed of coals is created, then smothering the fire by covering it with dirt (or quickly putting it out with water). The next day you dig up the firepit and you have a pile of charcoal ready to begin creating your own version of Terra Petra. It's not the most efficient method, but it would have served multiple purposes; clearing the garden site, a cooking fire, a light source, possibly a clay pot kiln, and a charcoal oven.

Anonymous said...

For terra preta, I've been contemplating feeding lump charcoal in a warm mash to hogs to take care of the grinding and the spreading. Haven't had the land or a chance to try it yet, but figured you might be able to make use of the idea.

Rich said...

The turkey was domesticated in the Americas during the time period that terra preta was being created, and turkeys (and chickens) need grit to grind their food in their gizzards.

If the turkeys were occupying the terra preta sites, they would have been consuming the larger pieces of charcoal left from the land clearing, cookfires, etc, using them as grit (grinding them to powder), and distributing them across the entire site.

I haven't seen any references to the presence of turkeys on these sites, but it makes perfect sense that they would have played a role in creating these soils. It is amazing that pastured poultry might have helped create the terra preta soils that the legend of Eldorado was based on.

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