As gardeners, we can design elevated soil beds to maintain proper hydration and create an environment that supports a myriad of life, known as a soil food web.
A healthy soil food web is filled with billions of microbes and larger organisms, such as earthworms, working together. Healthy soil promotes the process of nutrient development and delivery (to plants).
In other words: don't feed the plants. Feed the soil so it can feed the plants.
Soil food webs are complex, so building a healthy ecosystem doesn't mean going to a home improvement store and buying lots of garden soil to fill all your raised bed space. Sure, you could go that route, but it would be expensive, and it wouldn't give you a strong growth medium. You have established a healthy growth medium.
Build Your Garden Soil
Over the years I have developed a variety of elements that have brought me abundant gardening success. The method I describe here is not like a soufflé recipe. I'm not going to tell you that you have to add a teaspoon or 12 oz. That. My method - like my soil - is organic. Every time I follow it, it's different. These are estimated percentages that work for me, but they don't need to be exact.
I use a mixture of organic materials to create diverse mixes. As mentioned earlier in this series, I don't recommend cutting corners when it comes to cost. One of the things I learned early on is that you get what you pay for. Your biggest investment is in your land. Plant health and crop success depend on it.
Don't expect perfect soil the first year. Creating quality soil is a process that spans growing seasons. The methods I describe for you here will establish a healthy soil foundation that will develop fertile soil for the following seasons.
I do recommend that you mix all the ingredients together when initially filling the raised bed. Combines well so that elements can be introduced to each other properly. When I get into soil maintenance later on, you'll see why I don't mix established soil, but rather to "get the party started" - mix everything up and mix well.
The American Compost Council encourages all gardeners and growers to "go all in." This refers to the target of 5% (by weight) of total organic matter in soil.
A rough estimate to make this 5% happen is to include about 30% of the total organic material. All references here are by volume and - again - approximations only. So with that in mind, here's how I achieve those magic percentages:
50% High Quality Topsoil: This makes up the majority of your bed.
Buy topsoil in bulk or in bags. If you're buying by the bag, buy a trusted brand and check the ingredients, which are often regionally sourced.
If you need more than half your pickup truck load, I recommend buying in bulk. Find reputable landscaping suppliers through referrals. If you don't know someone who can provide a referral (or even if you do get one), take the time to talk to the provider. Ask questions about the composition of topsoil. I even check it out by sniffing and squeezing it (well, I've been known to taste it once in a while).
The squeeze test is just taking a handful and squeezing it. It should stay together, but when you run your fingers through it, it comes apart easily. If it's sticky or hard to come apart, it's too heavy. First, too much sandy soil won't stick together.
A good topsoil should not be sticky or sandy. It should lean toward the darker side of brown rather than gray or clay, and should smell earthy -- not rancid.
Note that I check bagged soil the same way. I never open the bag. I look for a torn bag - there is usually at least one.
When in doubt, look for certification marks from some nationally recognized organizations that indicate that the soil contains certified compost. Using certified compost as an ingredient, you can be sure that your topsoil will be of good quality too. You don't want to make the same mistake I did - not checking the quality first and then not shipping it to your door. I found a bunch of fill in my land - not the topsoil I ordered.
It is not uncommon for suppliers to provide fill soil as "top soil," and you don't want to start your bed with fill soil.
30% High Quality Homemade or Certified Compost: Use when possible, but vary when obtained from a reputable supplier.
I do a lot of composting at home, but not enough. Therefore, you will most likely also need to buy more compost than you produce. Not all compost is created equal.
My suggestion is to do your homework. Suppliers may have some printed information about their products. If not, please take the time to talk to the supplier here as well. Ask questions about how to make compost. Questions like this one:
Where do their ingredients come from?
What materials do they accept?
What do they not accept?
How do they make compost?
Your common sense will help you recognize any red flags. Don't be afraid to leave a vendor who doesn't provide a good answer. Compost is an investment, so choose wisely.
An easy way to make sure the compost you buy is safe is to find a supplier that offers certified compost recognized by the American Composting Council. Their website has some solid recommendations and a database of composting members. This is how I buy bulk compost and I have never been disappointed.
Top six organic materials to add to topsoil and compost:
Leaves: Chopped aged leaves are one of my favorite additions. They're free (I'm a frugal person so I like that) and they add up a lot. So what do I mean by old age? I chop up the leaves, moisten them, and within six months to a year they are rotten and ready to combine.
If you don't have enough leaves, ask around. I guarantee friends and neighbors will be happy to share their supplies.
Mineralizing Soil Mixtures: In another instance, finding a good landscaping supply company is important. Years ago, I discovered the value of adding mineral-rich soil. It has had a dramatic effect on the success of all the plants in my garden.
Minerals are the most important ingredient and no one seems to talk about it much. You can learn more about mineralized soils on my podcast.
Mineralized soil mixes are widely available and are usually sourced locally; so its composition will depend on your region. Granite is ubiquitous in the Atlanta area, so most mineralized soil mixtures here are made from granite dust. Azomite is another common and good choice.
Vermicompost (vermicompost): When I add vermicompost (aka vermicompost), I notice a drastic change in my garden. If you can find them in bags or in bulk, buy them. While not readily available, it's not cheap; it's well worth it. Fortunately, a little goes a long way. You don't need much to make a big difference.
The worm excrement was significantly higher in all the major nutrients that plants need to thrive. In fact, the worm poop contained five times the nitrogen, seven times the phosphorus and ten times the potassium of ordinary topsoil.
Castings add a layer of complexity to the overall soil composition. talk. ..enough is enough; this medium is one of my secret weapons for creating high-yielding garden soil.
Mushroom Compost: This dark brown, pliable, organic material isn't made from mushrooms.
It is a by-product of the mushroom growing material - what is left over after the mushroom is harvested.
Mushrooms are grown in a mixture of natural materials such as hay, gypsum, corncobs, cottonseed hulls, etc. But when the material is composted, bagged and sold as mushroom compost; it's light and brittle. It contains about 3% nitrogen and potassium, a small amount of phosphorus and other additional elements such as magnesium and calcium. Since it is a neutral pH (6.5-7.0), it will have no effect on your soil pH.
Land: There are many kinds of land to choose from, but pine wood is the most common. While pine bark is slightly acidic, I've never found it to have much of an effect on the overall pH of my garden soil. Be sure to use aged bark for this application. During the initial decomposition, newly felled wood will plunder from the soil rather than benefit it.
Ground bark is a good source of carbon. It breaks down over time, and its rough texture provides room for water and oxygen to move through the flowerbed. Topsoil, compost, and most of the other ingredients I've listed here have a similar texture. Ground bark comes in a variety of particle sizes that can really enhance the health of your plants.
Composted cow or poultry manure: Fully composted animal manure has been the backbone of organic soil fertility for thousands of years as it increases the variability of nutrients, organic matter and particulate matter to replenish the overall soil composition. That hasn't changed. What has changed are farming practices and the resulting manure risks.
Composted manures added to today's garden soils may contain synthetic herbicides, which are still effective even in well-composted manures. For this reason, I recommend that you use cow or poultry manure rather than horse manure.
Buy composted cow or poultry manure by the bag and from trusted sources. Buyer beware if it is an off-brand item or if you are buying in bulk. Many people have poisoned their soil with deadly compost (me included), inadvertently adding herbicide-contaminated ingredients commonly found in horse manure.
I no longer add horse manure - because horses are more likely to eat hay from fields that have been sprayed (or over-sprayed) with persistent herbicides. Persistent herbicides do not break down for years. It passes through the horse's digestive system and goes through the composting process without losing any of its lethality. Traces of herbicides, no matter how minute, can kill or disrupt the normal growth habit of many garden foods that are as effective after composting as they were on the day they were made.
There may be sources of horse manure that you actually want to use. In this case, you can take a biometric test. Do this simple test before letting manure come into contact with plants, soil, or compost. I failed to biometrically test my GardenFarm's horse manure and I suffered the consequences for four years.
These are the "ingredients" I use. Here are the ingredients I don't use:
Horse manure: It bears repeating. If you want to use horse manure, be sure to check out the biometric testing link. That little bit of time can save you from years of grief.
Sphagnum moss: This might be surprising. However, peat moss is not a sustainable material. It takes hundreds of years for peat to form in a peat bog.
Did you know that peat moss can destroy the soil's ability to absorb water? Ironically, it's often recommended for its water-retaining abilities. It can help retain moisture, but once the peat moss dries out, it can be difficult to rehydrate. Have you ever watered a container that has dried out, but the water just rolls off the surface? Usually, this is due to sphagnum moss in the container soil.
Faux Fill: While it may be tempting to use fill to take up space when you first build these raised beds, I recommend against them. Even organic fillers can be problematic, although they can save you some initial cost. Over time, they will break down and the surface of your garden bed will sink, requiring you to add more soil later.
Most importantly, the filler will block drainage. I know, it's counterintuitive, but research has proven it. I performed the tests using the container so you can see for yourself. Whether in a small space like a shipping container, or a large one like a loft bed, the science is the same.
Fill with Dirt: This is also an attractive way to save money, but it can get in the way of all your other efforts to create a healthy growing environment.
What is padding? It lies beneath the first few inches of dirt on the ground. The first layer of the earth is the topsoil; it's naturally formed - with varying degrees of health - organic matter, light and air, and other good stuff that occurs naturally near the surface. Fill is below the topsoil and does not include the inherently good qualities of the topsoil.
Some additional materials worth considering as additives:
Biochar: I've heard good things about Biochar. I've only recently started adding it to my garden, so it's too early to give you any personal opinion. Biochar does have some nutritional value. It's a pure carbon source that doesn't break down, but it does help plants use existing soil nutrients.
Fire Ash: I recommend against putting any fire ashes directly into your garden beds. If your fire ash is all woody, it makes a good addition to your compost (in small amounts). Do not use charcoal ashes as it may contain some ingredients that are not good for your organic garden.
Mycorrhizae: This fungus is very popular as a soil ingredient in bagged products. Healthy native soil usually already has this fungus (but don't use your native soil in your beds). Adding mycorrhizae to soil may offer benefits. Regardless, it doesn't do any harm.
Like containers, raised beds will leach nutrients more quickly; therefore, as a final step, it's best to add some slow-release, non-synthetic, nitrogen-based fertilizer (such as Milorganite) to the mix. It's like adding a cup of cocoa powder to your latte - plus a little extra kick.
maintain healthy soil
Building your initial raised bed garden setting with quality ingredients will yield good first season results. However, those crops you grow will constantly draw nutrients from these beds.
Just like with your bank account, it is vital that your deposits keep up with (or preferably exceed) your withdrawals. how do you do it Amend the soil once or twice a year with organic nutrients (like those I describe above) instead of synthetic fertilizers. By amending your garden beds, you'll see better soil for the second season, richer soil for the third, richer soil for the fourth, and so on.
Good soil and good wine; it gets better and better with time.
Before you improve your soil for the first time and approximately every two seasons, I recommend that you do a soil test. You can contact your local county extension office and the test is very cheap ($20-30). A soil test will identify soil pH and imperfections to help guide your amendment choices.
The nutrients you provide to the soil will be optimally absorbed by the plants when the soil is at a neutral pH. Therefore, it is important to understand when and how your soil pH is off and how to rebalance it.
Sometimes, I will gently scrape the compost onto the bed, but I usually just put the compost on top, cover with mulch and walk away. Why? Remember the microbial gatherings that started when we first built bed soil? Well, all these microbes are getting along so well right now, and they can't wait to see more. So, naturally, they quickly throw all the compost back at the party with everyone else.
