One of the most important pieces of any good garden is the soil. Good soil is essential to healthy plants, and using poor soil is a quick way to kill your garden. Soil is, after all, where plants get all their nutrients. Today we’ll look at what makes up soil, and how you can tell where your soil sits. We’ll also look at some quick tips to improve your soil if it’s not quite where you’d like it.
What is Soil?
Soil is a mixture of mineral and organic matter that plants require to grow. Good soil is rich in nutrients, and encourages healthy plant growth. Good soil is a key for plant growth as it helps keep your plants fed. Bad soil on the other hand can kill your plants, as it lacks things like nutrients or proper drainage.
What makes soil good for plants can get really complex, but for most of us it comes down to two things. That is, its ability to hold nutrients, and it’s drainage. You’ll see that different types of soils do both of these differently, and understanding how your soil behaves is important to achieving optimal plant growth. Different types of plants require different soil, so it’s also important to match your soil with the plants you plan to grow.
Soil Vs Dirt
In a lot of cases you’ll probably hear dirt and soil used interchangeably, but there is a technical difference. While soil is a great medium to grow plants in due to the aspects mentioned above, dirt is not.
Dirt, in a gardening sense, is referring to a medium that is devoid of nutrients; dirt is dead. It’s possible that overtime soil can turn into dirt once it’s lost all its nutrients. This is most likely to happen in a closed environment such as a pot where there is no natural processes replenishing used nutrients. That’s why it’s important to change the soil in your pots as we’ll see later.
This may seem a bit nitpicky, but it’s important to understand the difference and it’s a neat little trivia point.
Soil Nutrients (N-P-K)
If you’ve ever looked at fertilizer you’ve probably seen something like 10-10-10 on the side. This is the concentration of the three most important nutrients for plant growth; nitrogen, phosphorus, and potassium. While there are other nutrients that are used by plants, these are by far the most important for plant growth. This is important as healthy soil that’s good for growing will be rich in these three nutrients.
Nitrogen: Primarily used for leaf growth
Phosphorus: Used for root and flower/fruit development
Potassium: Promotes overall healthy growth in the plant
Understanding how these values interact can help you pick fertilizers that match your goals. For example, for beautiful blooming flowers you might want to go with a phosphorus rich fertilizer to promote flower blooms. Before doing that though, it’s always a good idea to get your soil tested to get a baseline. We’ll talk about that a bit later in this guide after we go over some other important characteristics of your soil.
In addition to the three mentioned above there are a number of other nutrients that are helpful in trace amounts. You might see these listed, but know that the three above are by far the most important for plant growth.
There are also certain elements that may be harmful to certain plants. This is why doing a test is important to not only figure out the good but also the bad in your soil.
Soil PH and How It Affects Plants
Another aspect of soil quality is the PH level. PH level is a measure of how acidic or alkaline your soil is. This score ranges from 0-14; a score of 7 is neutral, with less than 7 being acidic and more alkaline.
PH is important for your soil as it has an effect on how good bacteria and fertilizer work. Most fertilizers for example work best in a relatively narrow PH range. Outside of this range they are likely to perform poorly or be ineffective. If your efforts with fertilizer don’t appear to be working, your soil’s PH level might be the problem.
In general, a PH level of 5.5 to 7 is ideal for most plants, although some do grow outside this range. The further you get from it, the more likely you are to have issues with plant growth and fertilizer effectiveness.
We’ll talk at the end of this guide about getting a soil test, one of the things it will test is your PH. If you find that your soil is too far to one end then there are steps you can take to correct it. Be warned though, that some areas may naturally tend to move away from neutral based on environmental factors. If this is the case it may be difficult or impossible to make a long lasting change to the soil PH level and it might be easier to simply grow plants more suited to the environment.
Buying Soil at The Store
For many home gardeners, we get a good deal of our soil at the hardware store. This is a great way to get specially treated soil, but it’s important to understand the differences. Reading the package goes a long way.
For example, my local hardware store sells maybe two dozen different types of soil, and some are specially made for pots while others for outdoor planting. This has a lot to do with the drainage, but suffice to say using an outdoor potting mix in a pot is a good way to get your plants killed. Other soils come with varying amounts of organic matter, which is usually good except if you’re trying to grow seedlings. If you’re confused read the package, most manufacturers do well in describing which situations their soil is made for.
The great thing about pre-bought soil is it generally has correct nutrient level for growing. That takes a lot of the guess work out of gardening, and removes the need to actually test your soil.
Using Soil In pots and Indoors
Buying soil for pots and indoor use is completely different than for outdoors. There are two main problems with potting soil that can end up hurting your plants.
For one, there is no recycling of nutrients. While outdoors you have the constant breakdown of organic matter, in a pot you don’t have this same natural process. This means that eventually your soil will lack the nutrients necessary for plants to grow. Plants in pots need to be regularly fed and their soil’s nutrients replenished.
The next problem is that over time the soil in pots tends to compact. This leads to soil being too compact for nutrients and water to flow through it. Even with proper feeding eventually the soil will choke out the plant. This means that potted plants should have their soil switched out periodically. This should be done roughly once every 2-4 years depending on the plant and how fast it’s growing.
It should also be noted that using soil designed to be used in pots is a must. This type of soil is specially designed to be used in containers, and comes with the proper drainage and nutrients, which are different from outdoors.
You can easily see this difference by feeling the soil. Soil made for containers will feel much lighter and fluffier than traditional garden soil. If you pick up a bag of each, the potting soil will feel significantly lighter. This is done on purpose as it encourages proper drainage in your plant’s container.
As noted above, read the packaging and select the right soil.