 All right, let's wrap up tonight with a talk on soil organic matter. So we're going to talk dirt. There you go. Here to share her expertise on soils is Carrie Knudsen. Carrie is the horticulture agent in Grand Forks County. She received her master's degree in horticulture from NDSU. And now she's working on her PhD in soil science. Very impressive. Carrie has been working in extension for 15 years. Carrie, welcome to the forums. Good evening, everyone. And thank you for sticking around for the last session of the series tonight. And we're kind of going to go backwards. You've been talking for the past three weeks about how to keep things alive. And tonight we're going to talk about what happens when our plants die. So, but it's all good. Everything has a purpose, right? So tonight we're going to talk about carbon. Soil organic matter is essentially carbon. And we're going to get into the carbon cycle and how that should function in our environments. Then we're going to get down into talking about soil organic matter, the different forms that are in our soil, the roles that it has and how we build it in our soils. But before we get started talking about organic matter, I think it's good to kind of start with the basics to make sure that we're all on the same page. Our soils are mineral soils, and they're composed of about 45 to 42% mineral particles. So that would be our sand, silt and clay. And the other half of our circle there is air and water. And this is a fluid line between how much air and water we have in our soil. Last year with the dry conditions, we all had a lot more air in our soil than water. And then another component of our soil is organic matter. This little slice down here, typically between five and 8% for gardens, I think at least in Grand Forks County, we're around 3% soil organic matter. So where in the world is carbon? So on this graph, there's a couple or chart. There's a couple of things I want to point out as we go through our discussion. So the amount of carbon that's stored or reserved in soils is not that much compared to other places on Earth. And we do have carbon dioxide or carbon in the atmosphere in the form of carbon dioxide. And then our plants do account for a lot of the carbon, or not a lot of, they do account for some of the carbon and it can vary depending on season as you might imagine what plants are growing, their life cycles and different things like that. So what is carbon? Carbon kind of gets a bad rap lately, especially with everything that's going on. But carbon is important. It's a building block of life. It is part of organic and inorganic compounds. When it's in an organic compound, it can be used to build plant tissues or animal tissues. It's used for metabolism, how that organism gets energy. It's used to build membranes and plant membranes. It's in fats and waxes. A lot of our leaves have a waxy coating on them that helps the plant retain moisture. Wax begonias are named for that because of their waxy leaf on there. Carbon is also in carbohydrates and sugars and starches. Sugar can form long chains. They can be structural molecules like cellulose and hemicellulose. Those are the compounds that are going to give our woody plants or shrubs or trees the toughness that helps them stand up and be strong. And then starches, probably my most favorite carbohydrate if you've ever had a carrot or a potato or squash. You're eating stored carbon. And carbon is also part of proteins. We don't often think of carbon being in protein, but it's a part of its building block, along with nitrogen and sulfur. In terms of inorganic carbon, that's carbon found in gas and minerals. Examples of gases are carbon dioxide, carbon monoxide, methane, minerals, our fossil fuels, coal and oil and natural gas. And in our soils that can be stored as calcium carbonate, which is quite common in our soils in the Red River Valley. So hopefully, as you can see through this list, that carbon is important for living organisms. If we didn't have it, we wouldn't be here. It's important for the way the earth functions. It just is when it is in high amounts in the wrong places that it causes problems. So moving on, so we can understand how carbon functions in our environments. We're going to walk through just a very simplified carbon cycle. We're going to start right in the middle with carbon dioxide in the atmosphere. Now plants use carbon dioxide in the process of photosynthesis to make food, to grow tissue. And when that plant has waste, if leaves die or when the plant dies, and those pieces of the plant get incorporated into the soil, that's where we have soil organic matter. And then we have active and passive forms, and we're going to talk about that later. There are some producers that respire carbon dioxide back into the atmosphere. And then we have consumers, we eat plants. And then because of that eating and metabolism, we respire carbon dioxide into the atmosphere. Same could be said for cattle. And then our waste are when consumers pass away, their organic matter, it's incorporated into the soil and serves us soil organic matter. One thing I want to note about the carbon cycle is it is possible to lose carbon through runoff, leaching and erosion. A lot of times when we talk about nutrients, we think of more of nitrogen as the easily lost nutrient this way, but it is possible to lose carbon depending on how far it goes or where it goes so that it won't be returned into this usable cycle. And what discussion of carbon doesn't involve fossil fuels? Our fossil fuels are this soil organic matter, large pockets of it that's been stored and transformed over many, many years into our coal and oil and gas. And when that is burned, that's turned into carbon monoxide and can be transformed into carbon dioxide. We also have methane over floating over here too. There are organisms that use methane as part of their energy producing process and release it into the atmosphere and there are industrial processes that release it as well. So just kind of a quick cycle to understand how carbon functions in our environment and most of the time carbon wants to return to carbon dioxide. That's the main path that's going to go to so that it can be cycled through the system again. On to soil organic matter. First one we're going to talk about is active organic matter and it is different from plant litter or residue that is just laying on the soil surface. Active soil organic matter has to be incorporated into the soil whether that's by human intervention or organisms like earthworm pulling leaves down into the soil profile. It's fresh material that has recently, plants that have recently died, maybe it's a weed that you pulled from your garden and just left on top of the soil. It's still recognizable, it's still basic form and basic form is the same. When we talk about passive that's something different and it's a hot commodity in the soils. Microbes and organisms are using it very quickly. It's full of nutrients and it's a good food source in the soil. And if you've ever heard of the term labile organic matter that's the same thing just a different term for it. And then passive and active organic matter they can cycle in between each other as well depending on environmental conditions and how the soil is managed. Moving on to passive soil organic matter. Now this is different. It really doesn't resemble organic matter from when it starts out at the top to when it gets into the soil. It is chemically transformed essentially through the gut of microbes. And passive organic matter that's the stable organic matter that's stored in the soil. And it is stored when it is bound to soil particles. So on the screen here in the corner there's a picture, a very zoomed in picture of Kale and I clay. And I want you to notice that there is lots of different layers in there. A lot of times when we learn about soil or even when you have taught about soil we always use like it's a ball. It's a ball of clay, it's a ball of sand, it's a ball of silt. Well that's not actually how what the soil particles look like when you zoom in close to them. To me they resemble more like a book and with lots of pages. And within those pages there's lots of knowledge and information. And the organic matter can be stored in between those layers for instance in this clay particle. Now this is a different kind of understanding of how soil organic matter functions. Soil science research has advanced and we've found out that this is the more appropriate name for it instead of humus. We used to call it soil humus when I was first learning about soils and first in college but this is the mineral associated organic matter is the more appropriate term. And this passive soil organic matter that's stored and kept in the soil is protected by soil aggregates. And soil aggregates are just a natural form or structure that a soil has depending on its characteristics and then environments and they just help protect that soil organic matter from being can be taken in by microbes and then respired into the atmosphere. Now one thing to note that I think is especially important as we're talking about gardens and the health of our garden soil is the percentage of active soil organic matter that is turned into passive. It is less than 1% of the active organic matter is transformed into passive or stable soil organic matter. And it takes a long time to do this. And consequently when we're talking about increasing soil organic matter it takes hundreds of years generations to increase the soil organic matter that we have by a percent or more. A lot of times when we're talking about increasing our soil organic matter we're talking more about the active by adding compost and plant residues and not necessarily the passive amount of soil organic matter. So now that we know a little bit more about the carbon cycle and what soil organic matter is why should we care for our garden? Well it's a food source food source for micro microbes, different organisms in the soil and it creates a good habitat ecosystem for diversity. It acts as a slow release of nutrients. There are different nutrients like nitrogen, phosphorus and sulfur that can also be bound to those soil organic matter particles. Soil organic matter also increases the soils cation exchange capacity. It's a measure of how many, remember those layers in the book, how many nutrients can be stored in those layers and generally the higher number that you have the more nutrients that are available. Soil organic matter also increases a soils water holding capacity which is essential if you have a more sandier texture soil even more essential for all of us as we we may face another dry year in our gardens and it will help us use our water more efficiently. Soil organic matter also helps protect the soil surface not only from erosion but helps prevent soil crusting. So if you have seeds that have a hard time emerging often having a good amount of soil organic matter will help prevent crusting. Soil organic matter has lots of glues if you will and different chemicals in it that help stabilize those aggregates. So helping to protect itself but then it also increases soil pour space and reduces soil density which helps plant roots grow easier through the soil and helps keep a good balance of air and water in our soil. Soil organic matter also serves as has an ecosystem service it helps clean the soil and water as it passes through the soil profile. So how do we get from our tomato at the end of the season to soil organic matter that is in the active fraction and then store it into the passive fraction? Well, if you've ever composted before it's essentially the same thing it just happens in the soil. A lot of it has to do with the microbes and what their diet needs to be. If you composted before you know there has to be a specific or ratio of carbon to nitrogen so you can have that balance. If you have a material like sawdust that's higher in carbon it's going to take a lot longer for those microbes to break it down they're going to have to work harder and nitrogen might be more limiting in the soil whereas if you took your peas at the end of the season and laid them on the soil surface they're going to be a little bit naturally higher in nitrogen and the microbes will have an easier time breaking those down and might even release more nitrogen into the soil for other microbes to use. Just like composting temperature and moisture also affects the breakdown of the soil the carbon on top to the carbon in the soil the warmer the temperature the faster it will break down and moisture is needed for organic matter to break down those microbes need most of them need a water have to have water in their environment limiting nutrients to slow down how fast soil organic matter breaks down as I mentioned if there's not enough nitrogen or not enough carbon those microbes aren't going to be able to grow and do their jobs. PH can also slow down the rates if you have a very acidic a very basic PH that will affect it and the presence of oxygen is important as well if you've ever composted you're supposed to be churning your pile and the reason is that brings oxygen into the system a lot of the microbes not all of them but a lot of them are more efficient when they have oxygen in their metabolic processes and if there is no oxygen present and they have to move to a different form of energy conversion it just takes a lot more work for them to do it and it's going to be slower and then having a high micro population and having a diverse micro population in your soil are also key at getting that material on top of the soil that's just barely incorporated into the soil organic matter just want to take a little note out about microbes I think they are greatly underappreciated when it comes to understanding our soil and what our soil does for us they have a very important role in transforming organic matter in our soil all the carbon soil organic matter that is put in the passive fraction needs to pass through a micro so they are very important in that respect so I encourage you as a gardener to help your garden grow instead of thinking of how you are going to get the best tomato or what variety of squash you are going to grow is maybe how you are going to farm your microbes farm your microbes this year and the best way you can do that is building your soil aggregates and increasing plant diversity and we are going to talk about that in the next slide too but I also wanted to note there was a study and it was very thought provoking for me because in my education I always thought that if you had clay in your soil that meant you were going to have high organic matter well that's not necessarily true this is just one study I thought it was a good way to think about how we treat our soils and they found that the more diverse a micro community was the more stable organic matter was in the soil that affected the soil organic matter more than the soil particles so just because you maybe don't have the greatest texture soil just by adding taking care of those microbes you could get more soil organic matter in your soil more nutrient and water holding capacity as well so how can you build your soil organic matter well it's as easy as doing less work in your garden the first big thing because soil organic matter is stored in soil aggregates and because the microbes live in soil aggregates the best thing to do is to limit soil disruption I'm not saying that you have to do no till you can do reduce till you can use mulches or cover crops that will help reduce your tillage and also help prevent erosion because that soil organic matter is associated with the soil particles and the easiest thing for us to do is add plant residues so composting putting compost on your garden leaving debris at the end of the season to act as a mulch to help keep the soil there and not blowing away in the wind like we had this winter is easy to do as long as your plants are disease free and another helpful tip especially if you don't compost is just to cut the plants off at or below the soil surface leaving those roots intact so it's a food source for organisms in the soil and then you're not removing soil from your garden if you've ever pulled out a tomato plant or a zucchini plant there's always soil sticking to the roots and in this way you're keeping the soil in your garden and not in the landfill if you don't compost so I think that's all I have if there's any questions is there a practical method to measure the carbon to nitrogen ratio in a compost bin so as to maintain an optimal level I don't know of a way to measure it after you're composting it the best way is to measure what you're putting in the bin beforehand so the general rule of thumb is two parts brown to one part green you'll know if something's off if your pile is too wet and smell you might need to add some browns in there for more carbon and to help loosen up the pile too how about you mentioned the term reduced tilling so what is reduced tilling reduced tilling is let's say you normally till your garden just twice a year you till in the fall and in the spring maybe you don't till in the fall but you till in the spring or you could just till your garden where you're going to plant that year the row is or the hole and then use mulch or cover the soil in the other areas how about what type of what are you using for mulch between the rows photos yeah and the photo is that was just wood chip mulch but that was a learning experience as well because remember those C to N ratios there was a lot of carbon in the soil and we did have to make sure we used fertilizer because we did get some nitrogen deficiency in our tomato plants this is probably the third second or third year that we've used mulch over the top so we are seeing some of that effect okay you talk about the goodness of organic matter but can you have too much organic matter in the soil um yeah because you could probably get to I mean I that would be like a peat soil so yeah could um I think you can add too much um I would call it active and so you you might have issues with nutrients limitations and nutrient tie up as those microbes are digesting that material so I think the standard recommendation is one to maybe two inches of compost over the top of the soil um okay sounds good so you talk about leaving the tops of the plants lay on top of the garden at the end of the season as long as they're disease free so what do we do with that residue in the springtime um well I just plant into it I move it to the side um if I can get in there and it's not too muddy I might move things to the side to warm up that ground faster but I just move it to the side and leave it in my rows where I'm not planting for the current year so I don't have to get into that matter in roots in the garden could that encourage more weeds uh if you're leaving your weed it depends on the plant for the weeds so obviously if it's a perennial weed yes I would not encourage you to leave those in the garden to pull them up the best you can but if it's an annual weed and there aren't any seed heads on there then you should be fine it can so when we talk you know if you're holding your garden and you're just going very shallow in there you know that you're not going to do that much destruction I guess at that shallow over depth that's right so rotortillers are evil is that right yes if you're a microbe that's your biggest enemy yes is when you hear that rotortillers start up in the springtime that's when you worry how about can you throw eggshells and coffee grounds right into the garden right into the garden rose instead of lighting a compost first I wouldn't do it right where you're planting just because of tie up of potential nutrients but there's hit composting I do it I just don't do it where I'm going to plant the next year okay okay do you have any thoughts about biochar especially in a fairly sandy soil I think biochar is there's pros and cons to it it does add organic matter it's good at holding nutrients sometimes they come loaded with nutrients so it is a good thing but there's always a cost if you're talking about being more sustainable and more environmentally friendly where was that made how far did it have to be trucked from different things like that how much do you need to add to actually make a difference too how about cover crops are there any cover crops that you can plant in the garden either during the growing season or at the end of the growing season that is a very interesting question and that is actually the hearts of what I'm going to be researching hopefully in the next couple years I can't give you a research based answer based on agronomic crops there's just a lot of different variables I know gardeners who have tried ryegrass peas and different things like that it's more going to be trial and error on that one I got a question here I'm not quite sure but what can you add to clay soil regarding microbes is that to promote microbes to promote microbes just adding compost incorporating plant residues and then again trying to limit your disruption as well so you don't destroy the soil structure planning a diverse group of plants on top of the soil too will help increase micro populations and just any source of organic matter can help the clay soil to absorb water and improve its structure over time it's not going to be immediate but it will over time okay well you know soil formation takes millions of years right we have to be a little patient how about doesn't the winter in North Dakota freeze and ruin the compost when it's done outside does it ruin it does it kill the microbes can the microbes survive North Dakota winter can survive okay that's good to know how about can I just put kitchen scraps under mulch in the garden rather than use a compost pile evidently there was a famous gardener who did this just put kitchen scraps under mulch um if it's a couple caveats to that vegetable scraps yes I would still bury them in the soil unless that material has contact with the soil and the soil microbes that might just sit there it might start to smell you might attract things that you don't want in your garden so I would always suggest burying it in the soil okay how about can I use fresh or wet sawdust or wood chip material to apply as a mulch in a garden I think you have to be very careful with the wet sawdust just because it is so chewed up that and it is there it's easy to get mixed up into the soil and then that's when you're going to have your nitrogen deficiency because those microbes have a lot of carbon but they don't have a lot of nitrogen so it's going to be tied up I think you can do it just a very thin layer I wouldn't do it like wood chip thick like three to four inches buryingly that would be a disaster starvation your port tomato vine would starve how about can you compare leaves versus grass clippings as a mulch between rows I think either way they would work the ideal situation would be to mix them both together and combine them so you have a green nitrogen source if they're fresh grass clippings and if they're dried leaves they would be mixed to both worlds how about can I use ash from charcoal burned in my barbecue grill that's different that's not going to help your situation forget about that idea how about gypsum gypsum with my soil gypsum is good in soils for certain conditions I believe that saline issues are sodium issues in your soils but if you or your soil is okay and don't have those issues you don't need to apply it it's not as good as peat moss for those other types of soils just the sodic soils okay this person has just a general question they're very sandy soil in their backyard and they want to put in some raised beds do you have any recommendations about making or finding soil for raised beds finding soil for raised beds just a good loam which is a kind of equal mixture of sand silting clay that will have your best mixture of water retention and aeration as to where to find it find a neighbor or farmer who's willing to let you dig up some soil or a landscape contractor yep I get you can buy it you don't have to beg your neighbors for it how about epsom salts that must be great huh no nothing's good here no not recommended forget it okay now we got to look at the more worldly question here outside the garden what are your thoughts about carbon capture that's been in the news from energy companies um it is a loaded issue and I think there's good and bad when it comes to it because I remember we have the active and the passive um I think I haven't done a lot of looking into it but I did my class this semester we did look into it and a lot of it is just measuring active soil organic matter not the passive that is stored so it takes some looking into what actually they're going to measure and kind of the science behind it I think there's merit in it if it's done the right way and the science is understood okay that's a nice you handled that very well politically I had that for my final question so I was we're not going to let you go yet here we go these people just want to keep adding things here how about wood ash now that's got to be good for your soil huh because of our wood ash is highly basic and because our soils are basic enough or you know we are high on that pH scale it's just going to increase our soil pH other areas I know they added a lot because they have a more acidic soil you can add it but once again very sparingly it's not a lot I think it's like a I don't even want to say because it's just you don't want to add a lot to your garden area yeah our soils are too basic to begin with most of our soils so you're just you're dump it on your B lawn that's what I would do it dump it on your B lawn that would be because the grass can tolerate a little bit more more a basic chemical okay Carrie we're going to let you off the hook with that question thank you thank you for all that great information we're going to grow microbes this year not just squash okay sounds good thanks Carrie okay okay everybody that's it for tonight and I just want to especially thank all those great questions man I just saw such a wide variety of questions they really add a lot of depth of understanding and also add a lot of information so thank you and we do our best to keep the questions get as many of the relevant questions answered as possible but just keep them coming I really appreciate that and so we just we have one more night to go that'll be next Monday night we got really a series of special topics we're going to learn about cherry production in North Dakota how you can grow cherries in your backyard we're going to learn about some of the high value crops research going on in North Dakota and lastly we'll talk about long care during a drought which would be good for us in the West because we still have a drought and we'll have a discussion about long care after a drought which is good for the eastern part of the state because you got all this knowing and now your springtime looks really nice so thank you everybody and everybody have a good evening good night