Soil amendments have the ability to transform soil health by adding organic matter, changing soil properties and ultimately improving plant growth. In this episode of Granite State Gardening, UNH Extension’s Emma Erler and Nate Bernitz are joined by New Hampshire Agricultural Experiment Station researcher Becky Sideman to share proven tips and solutions for using soil amendments to build and transform soil to support healthy and productive plants in the garden and landscape. The conversation brings up topics and questions bound to get gardeners of all experience levels thinking about amending soil in new ways.
· Featured Question: How to manage ground nesting bees and wasps
· Featured Plant: Mountain Laurel (Kalmia latifolia)
· Closing Tip: Determining when compost is finished
Connect with us
Nate Bernitz 00:00
Welcome to the Granite State gardening podcast produced by UNH Cooperative Extension. Today we’re releasing part one of a two part conversation on amending and fertilizing plants in the Yard and Garden. Part One will focus on amendments whereas part two, which will release next Friday will focus on fertilizers. In this episode, you’ll learn some soil science, a lot about composted manure, adjusting pH, and what amendments are worth incorporating to build soil health and structure. Greetings Granite State gardeners. I’m Nate Bernitz, Public Engagement Manager for UNH expansion joined by horticulturist and UNH Extension field specialists to hammer earlier as well as Becky Sideman, a repeat guest on Granite State gardening now, Becky wears multiple hats at the University of New Hampshire. She is a sustainable horticulture state specialist for h, a professor of sustainable agriculture and food systems and the coordinator of that undergraduate program. And lastly, Becky is a researcher at the New Hampshire Agricultural Experiment Station. Becky, let’s start with some of the basics on soil health and building soil.
Becky Sideman 01:20
So I think of a healthy soil as one that holds soil moisture, and yet drains well. And it sort of acts like a sponge and all the good ways and contains all the nutrients that plants need to grow. So the macro nutrients like nitrogen, phosphorus, and potassium, and then all these little micro nutrients that plants need in tiny quantities as well. So often a healthy soil has a lot of organic matter, and it previously living plants and organisms that have died and make this really rich substance that is full of nutrients for our plant growth. So that’s kind of the ideal situation, I think that we’d like to get to,
Nate Bernitz 02:07
I find it a little bit confusing. And I may be the only one that’s confused by this. But how soil can both be a sponge and drain well, at the same time.
Becky Sideman 02:16
Yeah, it is sort of counterintuitive. But in a way, a sponge holds moisture. But it’s also at the same time not totally waterlogged. And so you really want the soil to behave kind of like a sponge, like it can really hold on to water. But that roots have to really work to get into the little nooks and crannies to get at it. Rather than like a bowl of water that’s just simply waterlogged. So that’s sort of how I, I kind of think of it
Nate Bernitz 02:50
fundamentally, what’s the difference between soil that drains wealth, or doesn’t drain? Well? And what’s the difference between a soil that retains water and nutrients versus not? And I guess, we’re kind of looking at soil that’s very clay based on one end, and very Sandy on the other, right?
Becky Sideman 03:13
That’s right. So a soil that is clay based, has really tiny little holes in it, like the clay particles are really tiny, and they pack together really well. And so this is something that holds water and nutrients really well, but does not drain. And I think on the other end of something like sand, which doesn’t hold water and nutrients terribly while and drains beautifully. And so ideally, what we would like is something that kind of blends, though the best of both of those worlds. And so you know, that’s why we we often look for sort of a loamy soil something that’s in the midst of those.
Nate Bernitz 03:56
And when you buy loam from your local landscape supply, or whatever, what what does that mean? And does loan mean something specifically? Or in that context? Or are we looking at two different things. One is the way a product is marketed and described the other is a soil science term.
Becky Sideman 04:18
That’s exactly it. So if you ask us soil scientist loam means a very specific thing. And it’s this, this intermixture this thing that holds all of these nice properties of clay and sand kind of uneven amounts. When you’re purchasing loam, they’re not using the soil science definition that just usually means topsoil and it might be clay or or sandier or some mixture there. And it’s it’s a little less certain what that is, but I think what’s most often meantt is topsoil.
Nate Bernitz 04:57
And we’ll we’ll talk about that a little bit later, but I It is really helpful to know that just because you’re buying something called loam, you still need to do your homework and make sure that’s a quality product, it is probably going to need a lot of work at the very least organic matter, unless it’s a super long product. And even then, these terms are just kind of thrown around. So it’s helpful to understand this stuff. This isn’t an episode all about soil science. But we’ll put in the show notes a link to a cool resource that we have on purchasing topsoil, that’ll give some really helpful considerations. Emma, when we’re looking at soil, plants grow in it. And I was wondering if you could explain how plants and soil interact, what plants are getting out of soil? What happens when plants roots are waterlogged, growing in really heavy clay soil or vice versa, what happens when plants roots are in sandy soil that’s not retaining and what a plants need, in general, are they getting everything they need from soil?
Emma E 06:15
Wow, a lot to unpack there. So I guess I’ll start with what plants are actually getting from soil. So first and foremost, the soil for the majority of plants is actually a way for them to anchor themselves. With the rare exception of some orchids, and some you know tropical other epiphytes, air plants, pretty much everything grows in soil, so it’s actually getting structural support from the ground. And then of course, the soil is where plants are getting the majority of their nutrients. Of course, some a lot of major plant nutrients are coming from the air. So plants need carbon, oxygen, these are these they’re coming from the air not from the soil. But for the nutrients Becky mentioned earlier, nitrogen, phosphorus, potassium and some of these other micronutrients, plants are getting those directly from their roots from the soil itself. And then the soils also holding on to water. plants, of course, also need water, we know that and with the exception of just a few tropical plants, those same ones that that don’t grow in soil, the waters coming from there. In terms of you know, what actually happens, you know, with plants and plants have different tolerances for how much water they need, what sort of drainage they need with the soil, even what sort of nutrients they need, or what quantities of nutrients they need. If you have a plant that likes a really well drained soil, so it likes that moisture to drain away pretty quickly after a rain event, let’s say and you grow that plant in a waterlogged soil. So a soil that has all of its pore spaces filled up with water. Typically, what’s going to happen is you’re going to start seeing some signs of stress in that plant if it’s exposed to these conditions long term. And a big reason for that is because that plant’s roots need oxygen. And if the if there’s no oxygen in the soil at all, if all that pore space is just taken up by water, and in a way plants can kind of drown in too much. Too much moisture too or too much water can lead to root rot issues as well. So fungal disease issues. Of course, some plants are adapted to live in this sort of environment. Think of all the aquatic plants that grow in ponds grow in lakes, but majority of upland species don’t want to be sitting in water. And the same is true the other direction. If you have an incredibly well drained sandy soil and you have a plant that’s more adapted to a consistently moist soil or even a wet soil, it’s going to struggle. So knowing the conditions that a plant prefers, knowing where it would live in its natural habitat is really helpful when you’re looking at planting things in your garden. With a vegetable garden. Of course, the majority of plants kind of enjoy the same conditions. So having a nice rich soil that’s well drained, high and organic matter, great. But if you’re looking at planting trees, shrubs, perennials, a lot of times we can have a really successful landscape without doing a whole lot to change the soil just by choosing things that are adapted to the conditions that you have in your yard.
Nate Bernitz 09:49
In general, generally in this conversation, we’re going to be talking about improving soil, and we may make some generalizations at times that might not apply to some plants that actually don’t like really rich soil. So that’s something to keep in mind that you really want to know the requirements of any particular plant you’re growing. And that’s why when someone test their soil through UNH, we ask what crops or plants you’re trying to grow so that we can tailor those recommendations. And both of you work with soil test results as Extension educators and interpret those results for people that send their soil to be tested by UNH. So can you tell me about the kind of a standard test what information is provided, why that information is useful, and maybe why there’s some information that we’re not providing, I guess nitrogen comes to mind. And of course, we’re sort of straddling the line here, again, of going into soil science. But let’s keep it really practical, why it’s worthwhile to test your soil as opposed to just adding good amendments, adding good fertilizers, and always just striving to improve
Emma E 11:07
what I think of right off the bat with with soil testing. First off, I guess, is being environmentally responsible, we can end up doing a fair amount of environmental harm if we’re adding nutrients that aren’t needed to the soil. It’s also true that certain plants grow better with the availability of certain amounts of nutrients, or probably even more importantly, with a specific pH to the soil. If you are getting just a standard soil test from UNH, or really any land grant university that has a soil testing lab, you’re always going to have the pH of the soil tested. So that’s a measure of the acidity of the soil. And then you’re also going to get some information on the available nutrients. So if you’re having your soil tested by UNH, you’re going to find out how much calcium is in the soil, how much magnesium, how much phosphorus, and how much potassium, these are all nutrients that that plants need. And in pretty large quantities, you’re also going to find out what the lead content of the soil is, which is helpful if you’re trying to grow edible crops, particularly vegetables, a little less concerning, if you’re just going to grow, you know, foundation shrubs around your house, you are also going to get a number that tells you how much organic matter is in your soil. And that that can also be helpful too, because we know that most plants are going to grow better when there is a significant portion of nitrogen in that soil. And again, that that are sorry, not nitrogen organic matter. So that that varies a bit too. So you’re going to get all these numbers that tell you, you know exactly what you’ve got, what your pH is, what how many, or how much nutrients are available. And whether that’s whether the numbers are low, optimum high, very high. And from there, the thing that’s helpful if you do get your your soil tested by a university lab is that you’re actually going to get recommendations then on what you should do to amend that soil. If you need to adjust the pH if you need to, you know, add fertilizer, which typically you do some recommendations there on on what sort of fertilizer ratio you should be looking for.
Nate Bernitz 13:39
Becky, when you’re thinking about soil test results in soil, what organic matter are you aiming for? Is there kind of a sweet spot that you want or more of a minimum? And is there a maximum? And why again, do we not provide nitrogen recommendations? And is there a relationship between organic matter and nitrogen?
Yes, certainly there is a relationship between organic matter and nitrogen. And maybe before I talk about organic matter, I’ll I’ll mention that I’ll answer your nitrogen question. So the reason that we don’t test for nitrogen and give you those levels when you submit a test is because nitrogen levels vary with environmental conditions throughout the growing season. So if we’ve had a rainy day and a big rainstorm and you collect the soil right, then a lot of the immediately available nitrogen will have washed out of that out of that soil down and then it those levels come back up. And so basically it’s so variable through the growing season that we wouldn’t be able to get an accurate read on it. Now, nitrogen is constantly released as organic matter mineralizes and breaks down and so this is Really, that gets to that connection between nitrogen and organic matter if you have organic matter in the soil, as it over time when it’s nice warm conditions, that gradually breaks down and releases nitrogen that can then be taken up by plants. And so realistically, the more organic matter that’s in a soil, the more nitrogen and other elements are going to be released regularly for your plants to take up. If you you asked if there’s like a target that we’re aiming at? And the answer is no. And we’re not, because different soils basically have different limitations. So if you have a very sandy soil, you are unlikely to be able to raise that organic matter very high, it might be as low as 2%, or sometimes even less, despite pretty aggressive amendments of organic matter. So and that’s okay, that’s the soil that you are working with. Whereas other soils, maybe a heavy clay soil, might innately have a soil organic matter of somewhere around six or eight or even 10%. I once had a soil test that I was reviewing that I thought had to be a mistake, because it said it was 45% organic matter. And it turns out it was taken from a peat bog. So it really was 45% organic matter. But that’s unusual. When you ask if there’s too if it could be too high. Yes, it really could be too high. And if you have amended with so much organic matter that it becomes as Emma referred to earlier, sort of an environmental issue, where you have added so much organic matter that it is releasing nutrients that are just leaving into the environment. And you know, contaminating waterways and so forth, so you can get too high. I would say practically speaking, that’s that’s hard to do in a garden setting. But it’s possible. I think it’s unusual to see rates of organic matter in a garden setting much over 10 or 12%, although it’s possible,
Nate Bernitz 17:26
and you keep mentioning organic matter. And so I feel like that’s a really good segue into talking about amendments. How would you characterize the difference between amendments and fertilizer? Number one? And what are some of the sources that are available to gardeners for adding organic matter into their soil?
So the difference really between an amendment and a fertilizer is that an amendment is it is providing some nutrients probably to the crop, but it’s also contributing to the structure and the biological life in the soil. So things that are amendments, and it may or may not be providing a lot of nutrients right away to the crop. So things that are great amendments include things like composts, manures, leaf mulch, these kinds of things. Sometimes rock powders, stuff like that, that’s going to build to add to the long term health of that soil, but not necessarily a ton of nutrients in the short term. Fertilizers on the other hand, are all about the nutrients, and they are providing readily available nutrients that plants need to grow. But they may not be doing anything favorable for the soil structure,
Nate Bernitz 18:53
Emma, on the ornamental side of things. Do you think about organic matter differently? And are there different sources of organic matter, you may rely on more,
Emma E 19:03
I don’t know that I necessarily think about it differently. The majority of plants that you could possibly grow in your landscape are going to benefit from having more organic matter versus less. There are of course plants that are evolved to grow and let’s say a very poor sandy soil. So some of these probably actually will do a little bit better if you have a leaner soil that does drain really quickly and doesn’t have a whole lot of nutrients to it. Just think of for example some of these things that that grow and really Sandy dry slopes. One of the first plants I think of is sweet Fern, which is a plant that will do you know pretty well if you have it in a in a rich soil but it will thrive if you have it in a dry Sandy situation where it’s you know evolved to grow so So, if you’re trying to grow the maximum diversity of plants in your landscape, particularly if you’re trying to grow a lot of things that aren’t necessarily native to New Hampshire, if you’re trying to grow things that come from Asia, let’s say, or Europe, having just a really rich loamy soil that drains well, but is high in organic matter, is probably going to help you grow the maximum diversity of plants you could possibly have in your landscape. But like Becky mentioned before, too, depending on your soil type, you may not ever really be able to get that organic matter high enough anyways. So if you have a very, very sandy soil, and you’re looking at a permanent landscape planting like trees, shrubs, perennial beds, it’s going to be hard to add enough organic matter to really change that soil because you’re not going to be able to incorporate it, meaning mix it into the soil once those plants are established. So you’d be looking at just putting a layer down on top. So I’m always really thinking about what the conditions are naturally, and what’s going to grow their well on its own without having to make a lot of changes. Although that being said, I absolutely think that that top dressing with organic matter. So composts mulch, probably most importantly, is key in the ornamental landscape.
Nate Bernitz 21:31
We’ve got to take a quick break here. This isn’t an ad per se, but I do want to plug our spring webinar series, we’ll have the requisite links in the show notes. But we have upcoming webinars on supporting pollinators in your landscape, getting the most out of compost and manure and using drip irrigation in the garden. These webinars introduce a visual element to what we’re doing here on the podcast. I hope you’ll check them out. Alright, thanks for indulging me. Let’s get back to my conversation with Becky and Emma. I’m going to make a generalization here and jump in for context and nuance. But it sounds like adding organic matter like compost or manure is generally always a good thing. But there are two reasons why you might hold off. One is environmental considerations. And the second is practicality and cost. If you’re not going to be able to fundamentally change the organic matter of your soil based on its texture class. Maybe you don’t just continue to pour money into organic matter materials are where am I overgeneralizing with that statement?
Emma E 22:47
Well, if you make your own compost at home, so you’re not spending any money on it, then I think certainly keep making that compost keep keep adding it to your garden particularly where you’re growing annual crops so your vegetables or annual flowers where you are able to really incorporate that eye even if you have a very lean soil. I think top dressing can help a lot and that that’s true for lawns certainly with you can top dress lawns with a thin layer of compost you can do the same with with trees, shrubs, perennials, and there are absolutely benefits to that.
Nate Bernitz 23:31
Well, it’s time for this episode’s featured question. How do I get rid of the ground bees in my lawn? When I get this question and we get it every year. My first thought is whether someone’s talking about one of our native bees one of our large solitary digger wasps or an aggressive social wasp like yellowjackets, New Hampshire has many species of native bees that dig individual nest burrows and soil bumblebees also sometimes nests in the ground, but they’re social bees. Ground nesting bees like bare sandy soil with sparse vegetation. Ground nesting wasps, like the great golden digger wasp and the cicada killer wasp, are large and can be scary to those who don’t know what they are. Sometimes people think they’re hornets or aggressive wasps, because they’ll see many in a small area. And again, they’re large, but what these wasps they all have individual burrows and are their numbers because the soil is favorable to them. Again, sandy and bare. These solitary nesting wasps and bees are not aggressive and are considered beneficial. to discourage them from nesting in your lawn. We recommend adding organic matter like compost and using fertilizer and irrigation to aid your overseeding efforts you can increase the density of the grass. This may not deter them this year, but could deter them next year. For gardens again, introduce some organic matter and use mulch to keep the soil covered. The use of an insecticide should really be a method of last resort keeping in mind, the solitary bees and wasps are not aggressive and beneficial. Lastly, I will mention that most yellow jackets will excavate a nest chamber underground and can be quite aggressive. My best advice is to learn what yellow jackets look like, what our native bees look like, and what the common solitary wasps look like. So you know what you’re dealing with and whether they’re an aggressive species, and then you can go from there, we have a link to our fact sheet on bees, wasps and hornets in the show notes. And that is your featured question. Becky, in gardens, where a gardener is, year after year, adding lots of organic matter taking really good care of their soil in various ways. Does inorganic matter, like compost and manure end up being a substitute for fertilizer? And can it just be a substitute? Generally speaking?
Becky Sideman 25:56
Well, yes, over time, if there are high levels of organic matter and steady contributions to organic amendments, yes, they that will release nutrients. And it may even be enough to support the majority of crops that our person is trying to grow. I certainly think that’s true for for lighter feeding crops, that might be less the case for things that are really heavy feeders that require a lot of nutrients, like, what comes to mind is maybe winter squash or sweet corn, things like that, that tend to take a lot. As a general rule of thumb, although it’s not perfect, we estimate that each 1% of organic matter releases 10 pounds of nitrogen per acre per year, as it slowly breaks down. And so what this means is that if you have a very high organic matter 10% organic matter soil, you will be providing about 100 pounds of nitrogen to the acre, which is enough to support the growth of a lot of annual crops. So yes, I think it can replace, it can replace fertilizers, I will kind of caution that it’s not a total replacement for keeping an eye on what’s going on in the garden by testing every few years. Because you can have the pH wander over time either get far too high or far too low and say your crop growth might suffer for reasons other than not enough nutrients. So I wouldn’t say it’s a replacement for everything. But it it can be a long term plan for crop fertility for sure.
Nate Bernitz 28:03
So use case here, I build a raised bed, and I get 50% loam and I put 50% compost in there, that should be well over 10% organic matter. So am I All set? Do I need to fertilize if I’ve just done a 5050 blend of topsoil and compost and I just start planting? What’s going to happen?
Well, I think at the practical side of me says that you all compost are not created equal. And some compost are very finished and are releasing nutrients. Some are less finished and are actually tying up nutrients as they break down. And so I would be cautious, honestly, about approaching it in a single slug application like that. And assuming all it’s going to be good. I think that your former suggestion of a gradual application would be more likely to to yield good results. In the case, like you mentioned, if it were possible to have a compost analysis that would give you a little more information to know what you’re getting into and so to be able to predict a little bit better what that soil was going to be like, but you know, practically speaking if you were going to set that up, I would suggest taking that loam, mixing in the compost in whatever proportion you’re going to add, then test the soil so that you have some kind of sense of how what kind of nutrient levels and pH you’re dealing with at the end of that process. What would you add to that Emma?
Emma E 30:01
I guess one thing that just keeps going through my mind too, is kind of the difference between animal based composted manures versus a plant based compost. And I’m always coming back to kind of the environmental implications of both. plant based compost, you can use a lot of I think kind of really without limit. But with manure, sometimes you can start to have issues and manure is much higher and phosphorus, a lot of people but I’d say the majority of soil test results, I look at soils that people have on their properties are already high or very high in phosphorus. So just you know, being conscious of that, and knowing that putting down even more phosphorus year after year after year, could potentially lead to some environmental risks, particularly to freshwater bodies in New Hampshire. So if that phosphorus washes out of the soil, into lakes, rivers, streams, ponds, you could end up with algae blooms, and this is definitely something that we see in New Hampshire. So something to avoid, and that’s yet another reason to get your soil tested to rather than than just putting these nutrients in again, and again. And again. Because you may be adding something that you really don’t need or don’t want, there might be a better option.
Nate Bernitz 31:25
If you’re on a well, or should you be worried about water quality implications for your well for groundwater from maybe excess additions of organic matter, or fertilizer for that matter.
Emma E 31:39
Yeah, I mean, I think it probably depends a bit on your Well, you know, if it’s a just a dug well versus a drilled well. Considering what sort of fertilizer you’re using near your well is definitely something you should keep in mind, you can end up contaminating your water source, if you have too much organic matter, or you’re even if you’re using synthetic fertilizers. Well, that’s of a concern if you’re on city water, but a lot of people in New Hampshire on wells. So that’s it’s something you should be keeping in mind. I don’t, you know, depends so much though, on on the actual characteristics of your soil, you know, what its structure is like, what the the fate of those nutrients is going to be? So just just something to keep in mind. And I probably would be trying to avoid using excess of fertilizer excess organic matter right near my well, or in general.
Nate Bernitz 32:40
Right? Yes, Becky, how to cover crops for the gardener fit into this. As far as being a source of organic matter.
Cover Crops can be a great source of organic matter. I would say that the cover crops that I recommend for small garden situations are the ones that die over winter. So they’re easy to deal with in the spring, or that are easily incorporated in the main growing season like buckwheat or something like that. And so these tend to be smaller bodied plants and therefore they just take up less nutrients and they release less nutrients and they provide less organic matter to the soil than some other. Some other sorts of cover crops that are a little more aggressive. In general, it’s, I think of cover crops as a tool to catch and hold nutrients over the winter months so that you don’t lose them. But not really as a way to in a meaningful way increase the organic matter in a garden setting. I think they serve important good functions, but I wouldn’t consider them a really big beefy organic matter amendment.
Nate Bernitz 34:06
You mentioned losing nutrients over the winter. So you’re saying not only are plants using the nutrients you’re providing in the soil, but you’re also naturally losing nutrients over the winter. Can you say a little bit more about that?
Yeah. So the nutrients that plants are taking up from the soil are held in various ways around and on the outsides of soil particles. And so when that soil is filled up, those those pores between those particles are filled up with water. those nutrients dissolved into that water and if plants are there and growing, they can take them up. If they’re not, and that water then leaves by runoff or erosion, the nutrients can go with it. And so when we have rainy falls and rainy springs, which is what we always do, then that can be a time when we lose a lot of nutrients if you have. So for this reason, like if you have plants growing in the summer, whether they’re a perennial or an annual, or whatever they are, if you have plants growing in the summer, and they die in the fall, or they go dormant in the fall, if you cut them off and take the tops away, but leave those roots in place, those roots are holding a lot of nutrients right there that are going to become available the next year. So that can be I wouldn’t, don’t pull them out because they are going to actually become part of your valuable organic matter going forward.
Nate Bernitz 35:42
Interesting. So it sounds like just a few takeaways. Cut plants at the soil line rather than yanking them out using cover crops or mulch, or both, to both prevent erosion and prevent leaching of nutrients, loss of nutrients. So those are good things, would you have any hesitation in the spring, about just dumping a load of manure from the farm down the road, you know, maybe you get it cheap or free, load up your truck, bring it in and just dump it into the garden and then get planting? Because I I certainly hear from a lot of gardeners who do do just that. And I think hey, sounds like a great source of organic matter. But any reasons to think twice?
Yes, there are some reasons to think twice. Probably the biggest reason to think twice is that manure carries lots of pathogens in it as well as good things. And so, you know, if it’s, we consider it not really a problem if it’s applied the fall before or the summer before growing a vegetable crop. But if you have fresh manure or manure that hasn’t necessarily gone through a really rigorous high temperature composting process, there is a good chance that it has eColi and other enteric bacteria in it, which are going to possibly pose a food safety concern. So that’s a different story if you’re growing ornamentals, but if you’re growing vegetable crops, especially ones that come in contact with the soil, I would be really cautious about and avoid a spring application of manure.
Nate Bernitz 37:29
And I guess my perspective is I see it being a lot easier to get manure than plant based compost, generally speaking, especially high quality plant based compost, it seems to just be in short supply. So while in theory, you know a lot of this conversation Yeah, add high quality plant based compost and you’re gonna see all these benefits, but can you get it? Can you get it affordably? That’s a different question. And every spring you see farmers advertising, that they’ve got manure, maybe they say it’s aged manure, or whatever. But how are you going to know whether manure has been composted at hot enough and sustained temperatures for long enough, as the person that’s selling it or giving it away even get to know, as there are a lot of questions, I guess, come come to mind for me.
Emma E 38:28
With plant based compost, at least, that’s something that people can hopefully be sourcing from their own properties. By composting, the types of plants that you cut and left the roots in your garden. Any leaves that came off of the trees certainly could be composting those as well as in kitchen scraps, too. So while that may not yield enough to really get our no jumpstart a soil to start with, if you have very low organic matter, might be enough to maintain your organic matter content in your soil going forward.
Becky Sideman 39:02
And it’s not I don’t think it’s a bad idea to get that manure in the spring if you have a place that you can keep it that’s protected from leaching and you know, bodies of water and so forth. And you can apply it to sections of garden as those become available. And, you know, for the next year, so for example, when you’ve pulled out your winter squash in the, you know, September, that’s a great time to put manure and then seed a cover crop or when you’re done with your rhubarb for harvesting mat for the season. That’s a great time to add that compost or manure that you don’t know what it’s it’s food safety history is the that’s a great time to put that on. And so it’s a great idea to get it but just manage it accordingly. I guess.
Nate Bernitz 39:57
Another source of organic matter is peat moss, what do you make of that as an option in or an or an ornamental or food production standpoint? Do you view it as a good source of organic matter? Is it going to change soil pH in any way? And are there any concerns about it?
Emma E 40:17
So peat moss is actually a product that’s mined primarily in Canada. So this is really ancient sphagnum moss , that that came from bogs that is degraded, and are broken down. And it it takes millennia for this to happen because this peat moss is, is growing in an area that’s extremely acidic. So that decomposition is very, very slow. And it’s really it’s considered a non renewable resource. Because there’s there’s only so much peat out there that we can possibly harvest. peat moss does have a lot of really wonderful characteristics. And it’s, it’s still probably the best growing media we have for potted plants, if you’re growing things from seed or from transplants. However, you know, adding it to garden soil, you know, while that can be really helpful, and it can definitely improve nutrient holding capacity of a soil It can also help improve moisture holding capacity as well. It I cannot recommend it for outdoor applications just because it really isn’t a sustainable option. If you’re thinking along those lines, then compost or even, you know, wood chips potentially that have broken down or been composted to a certain extent, could be used for the same reason. And actually, when it comes to even commercial potting mixes, some of these things are being looked at to see if they could be alternatives to peat because really, there is only so much out there. So that’s my take.
Nate Bernitz 42:09
We’ll get back to our conversation with Becky Seidman after Emma helps us take a quick break with her featured plant. Emma, what do you have for us?
Emma E 42:18
The featured plant this episode is mountain laurel kalmia latifolia. mountain laurel is one of the most beautiful shrubs native to New Hampshire. You can find it growing along forest edges, woodlands and wetland margins in various locations throughout the state. Though it’s most abundant and in the southern half of New Hampshire. mountain laurel is a multi stemmed broadleaf evergreen that is noted for its gorgeous late spring flowers and quality foliage. With age it develops gnarly branches that give it a unique look. Wild mountain laurel flowers range from pale pink to white with purple markings. Many cultivars have been developed for landscapes with an even greater diversity of flower color and markings. The flowers appear in terminal clusters that are about six inches in diameter, and each individual flower is about an inch across and is cup shaped with five sides. Mountain laurel is a member of the heath family, Ericaceae, which places it alongside other acid loving plants such as rhododendrons, and blueberries. It grows very well in cool rich acidic well drained soils and part shade that will tolerate a range of light conditions and dry soils. It is also largely ignored by rabbits and deer, which recommended the many gardens in New Hampshire. All in all, mountain laurel is an excellent shrub for tall borders, hedges or wild or naturalized areas. See if a mountain laurel can fit into your landscape.
Nate Bernitz 44:00
Let’s go through a few other amendments that we get a lot of questions about and there’s a lot of interest in starting with bio char. Becky, do you view bio chars as something gardeners should consider using in their gardens?
Wee, that’s a great question. There is some interesting research with bio char that has shown some positive effects of using it in certain research settings. At the same time, I have yet to be convinced from the research that a lot that a lot of the benefits are not due to its effects on pH and improving the pH in controlled settings. And so while there is good evidence that naturally biochar containing soils are really productive and healthy over the long term. I have yet to be convinced that this is a great amendment that’s worth the very expensive price tag. And so I tend to generally favor amendments that are local in origin, that you have access to that provide that that gets you in the right ballpark pH wise, and that increases organic matter, using things that are from here that you have in abundance. And so I wouldn’t recommend that a gardener go out of their way to procure bio char as a source of organic matter. For their garden, I would instead suggest focusing on sources of organic matter, which is what this is that that are local and origin.
Nate Bernitz 45:56
Emma for gardeners dealing with very clay, heavy soil, do you view sand as a soil amendment worth consideration?
Emma E 46:05
Not typically, I think the amount of sand that you’d have to bring in to actually change the soil environment would would be absurd. I think I’ve read that it needs to be you know, 50% or more of that soil matter needs to be sand. So that’s not something that I I would advocate for I instead would be encouraging people to be boosting their organic matter. Again, the organic matter is kind of the answer for all of these things. And with a really heavy clay soil to at least from you know, my perspective with landscape plants, there are there’s a good list of plants that are totally fine growing in a clay soil. And there’s there’s no need to really fuss over amending that to too much. So, yeah, I’d skip the sand, incorporate some good compost or or manure and make good plant selections.
Nate Bernitz 47:05
And other trendy soil amendment. Becky, is m ycorrhizae he would you recommend that to a gardener?
Well, I don’t I think in most cases I wouldn’t. But that said, mycorrhizae in certain settings make a lot of sense. For example, a lot of our potting mixes now, which are sterile peat based potting mixes things that we’d raise transplants and contain mycorrhizae . Because they have really clear known benefits protecting those young seedlings against pathogens, pathogenic organisms that are in the soil. So in that controlled setting, I think it makes a ton of sense. In a garden setting, I would be suspicious, and I would be skeptical that it would make a real difference in terms of performance. I know there are folks out there, there’s products that that claim to have really significant effects. And I would encourage, when I talk to growers who are interested in in sort of studying this, or trying it, I suggest that they try some with and try some without and set up their own little experiment to see if they can see a real difference in growth. I think a lot of what mycorrhizae do for plants is help them access nutrients and and reach nutrients that they would not be able to access otherwise. So in a forest ecosystem, this makes sense. In a garden setting where we’re providing nutrients for crops, I think it makes maybe a little less sense. Then in some other kinds of settings.
Nate Bernitz 49:00
Something that we haven’t talked a lot about is soil pH, which we know is important, although I’d like to hear a little bit more on why it’s important for what are the tools at our disposal to change soil pH and how long does that process take?
Emma E 49:18
Well, soil pH has a big impact on nutrient availability. So depending on what the pH is, some nutrients might be locked up in the soil or you know that they might be available to plants. Plants also have kind of a specific pH range where they are able to take up the the nutrients that they need. So that definitely varies by crop certainly or what you’re trying to grow. Let’s say blueberries, for example, are pretty happy with a really I should say they’re very happy with an acidic soil. So we’re talking about, you know, four and a half to five With a pH versus if you’re trying to grow lawn, the lawn really only wants that soil to be slightly acidic. So neutral, pH scale goes from goes to 14, and seven is neutral. So if you have a pH of let’s say, 6.5, that would be considered acidic. If you have a pH of, let’s say, 8.0, that would be considered more alkaline. Some people will call it call it sweeter. Or if you have an acidic soil, you might you might call it more of a sour soil. The vast majority of plants are happiest with a slightly acidic soil, because that’s when most of the nutrients are going to be available to them. But like I said before, that that can vary a little bit depending on the particular crop that you’re looking for. So that’s that’s where it’s really important to test your soil and get recommendations specifically for what you’re trying to grow.
Nate Bernitz 51:01
Back to. Do you have anything to add to that? Are people generally needing to nudge their pH in one direction or another. Is there a particular time of year when you should be trying to do that? Any other thoughts?
Well, our our native New Hampshire’s forest soils have a quite acidic ph 4.5 4.8, something like that. And so mostly, when we’re looking at trying to grow garden vegetables, we would be looking at increasing mat Ph. and we would do it by adding fine powdered limestone, or wood ash. It is there’s no rule that you have to add it at any particular time. But usually it’s added in the fall or in the spring, when it can be tilled and mixed into the fall like root zone of your garden space because that then it’s going to be able to act more quickly to change the pH. It doesn’t change the pH super super quickly with limestone, it might be over a year or two years. With wood ash, it is a little bit quicker, it might be within six months, something like that. But yes, usually you’re trying to raise the pH. But it is certainly possible to go too far. And I’ve heard a saying that the if you’re going to put wood ash on the garden, having the woodstove befall is not a good enough reason to put it there, you actually should make sure that the pH is is requiring adjustment, because if it gets too high plants really will not grow well, these very high pH is
Nate Bernitz 52:59
well if you’re constantly adding what ash and then you go out there with your at home pH kit, or maybe you send some soil into UNH, given how long it takes to adjust the pH, that reading may not fully account for all the material that’s in the soil too. So maybe constantly adding material might not be as good an approach as doing it once a year if needed, just so you can give that material time to actually change the pH. Does that make sense?
Becky Sideman 53:30
Nate Bernitz 53:32
There are some products that are advertised as fast acting like a fast acting line. Do you have any experience with those? And are we talking fast acting in terms of like less than a year, but still six months? Sir? If you get your soil tested in April, and it comes back that it needs lime? Can you add some of that fast acting lime and just get planting? and you’re good to go? Or? I mean, that’s a conundrum a lot of people get in, right? They get their spring soil test and pH is off and they’re like, Can I can I grow in the soil? Or what do I do?
Well, usually those faster acting products, a product changes the pH more quickly if it’s ground into finer particles basically. And so the finer the particles, the more fast acting that line is going to be. And also the more evenly you can get it distributed throughout the soil surface, the faster it will act. I think this is a relative question. And so if the pH is 4.0 and you’re trying to get to 6.8 or seven, or 6.5. That’s a long way to go. And so you will be unlikely to make that kind of a leap in a month. If it’s just slightly low, you could certainly garden in it. And adding the lime and then allowing it to come up over time is totally, totally reasonable. As Emma said, the reason plants do better at certain pH than others, is because nutrients are more or less available for those roots to take up at that pH. So the worst case scenario, if your pH is off, is that plants will have a harder time growing and taking up the nutrients they need. This I think is worth the gamble, you can certainly plant your guy would not plant a garden because the pH wasn’t perfect, I would just know Gosh, if they don’t do well, that might be why and slowly work on it in the future. But I would definitely not miss out on a gardening season because you’re trying to get the pH dead on.
Emma E 56:01
But maybe if you’re going to spend a bunch of money, let’s say putting in a new one, if your pH is let’s say 4.0. Maybe don’t invest a lot of money and all the seed and fertilizer and everything when it’s not going to grow very well. So that that might be a good opportunity to maybe get that get that lime down in the fall. And then do your planting in the spring or or vice versa, give it give it some time to go to work before you’re spending a whole lot of money on something like that.
Becky Sideman 56:35
Yeah, kind of on the same vein, people if you’re going to plant something like 75 blueberry bushes, this is an investment. blueberry bushes will not thrive. If the pH is high, like a six, six and a half, it is worth taking the time, even if it takes a year or more to bring that pH down before investing and putting all those expensive plants into too high pH soil. That would be problematic.
Nate Bernitz 57:09
What are you going to expect to see long term from, say a blueberry bush or an apple tree or something like that, that you plant in soil that needs a pH change. And in planting it, you’re also adding the lime or sulfur that that soil needs are there going to be long term repercussions for the help of health of that plant for not being planted in soil that was at the proper pH from the beginning.
Becky Sideman 57:35
There can be I can speak from the experience of seeing blueberry plantings that were planted in, for example, former lawns or hay fields that were very high pH beautiful for grass poor for blueberries. What happens is the plants just can’t take up nutrients while and so they just kind of flounder and they don’t grow well. And on the flip side, the grass that is there grows great. And so you tend to see a really slow start, and possibly more winter injury and other like succumbing to other stresses. And so yes, I think you can see kind of long term problems. And it’s harder to change the soil pH once you have a perennial crop growing there, because at that point, all you can really do is put amendments on the top, you can’t really tell it in and so you have less ability to really affect change than you do before you plant.
Nate Bernitz 58:45
So closing question for part one of this discussion on amendments and fertilizers is kind of this almost existential question that you may run into. When you’re not getting good results you’re and soil is to blame. And whether it’s a lawn or a garden, maybe you have a bad just a terrible year in your vegetable garden and you just kind of want to start over. wipe the slate clean or your lawn. It just it just seems hopeless. And strategy could be just kind of removing everything and then trucking in more material. How do you make that determination of buy soil or build soil?
Emma E 59:37
Great call. I mean, I think more often than not, I mean bringing in enough soil to totally replace what you have, particularly if you have a decent size property is probably going to be more than what most people are going to be willing to do. I think what people will sometimes do let’s say for a lawn area is come in and Put down, let’s say just an inch or two of new loam overtop of what they have there already. But that may not be enough for you really to have an impact. With that that shallow layer, because most of a lot of the plant roots are going to extend beyond that layer. If you are adding something like a super loan to that comes with, let’s say 50% comp is supposed to come with 50% composts, and at the start, that organic matter is going to disappear over time. And you might just kind of be left back where you started, if it’s more of a sandy topsoil that was mixed in there to begin with. So unless you’re dealing with, let’s say, an area where all the topsoil was removed, you’re in an old gravel pit or a development where most of the topsoil was scraped away, for whatever purpose to reshape the land. Or if you’re living in or if you’re home and garden areas in a place with contaminated soil, let’s say soil is really high and heavy metals, then it might be appropriate to bring in some new soil either to you know, replace what’s there, add to it. Or, you know, in the case of heavy metals, maybe create just some raised beds where you add some some soil that doesn’t doesn’t have these heavy metals in it that you can grow food crops in. But if you’re just dealing with more of a sandy soil or clay soil, I think you’re probably better off just working with what you got. And amending it as best you can. And eventually, you’ll probably find out too just by trying to grow things what’s going to work for you really well on your soil and, and what’s not. I want to share one last tip with you before we go. If you compost in your backyard, you may be wondering how to tell when your compost is finished and ready to be used in the garden. The amount of time it takes to produce compost depends on several factors, including the size of the compost pile, the types of materials, the surface area of the materials, and the number of times the pile is turned. Large piles that are between three to five feet cubed, that have the perfect ratio of green to brown materials and are turned frequently can be ready in about three months in the warm season. Whereas a smaller untended pile may take a year or more to decompose. You’ll know your compost is completed when the pile is about half its original height, and there are no longer recognizable pieces of yard waste or kitchen scraps in it. Also, finished compost will have an earthy pleasant smell. Once you’ve determined that your compost is finished, you can start using it in your garden, either tilling it into the soil or applying it as a top dressing to the lawn vegetable garden flowerbeds around trees and shrubs.
Nate Bernitz 1:03:23
We’ll be back next Friday with part two of this conversation which focuses on fertilization. You can reach Emma and I by email at GSG.firstname.lastname@example.org. We’re loving your questions, feedback and suggestions. Looking ahead a couple weeks we’re going to do episodes on getting the summer garden going and on pest management in the vegetable garden. If you have questions for those topics and them our way and we’ll feature as many of your questions as we can keep on amending your soil Granite State gardeners we’ll talk again soon. Granite State gardening is a production of University of New Hampshire Cooperative Extension and equal opportunity educator and employer views expressed on this podcast are not necessarily those of the universities, its trustees, or its volunteers. inclusion or exclusion of commercial products in this podcast does not imply endorsement. The University of New Hampshire US Department of Agriculture and New Hampshire County is cooperate to provide extension programming in the Granite State. Learn more at extension.unh.edu
Soil Amendments, Ground Nesting Bees, Mountain Laurel and Finishing Compost is written by Dave Kellam for extension.unh.edu