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Gardening 101: Understanding Your Garden Soil
Imagine if you did one thing that could prevent 80% of the problems in your garden.
Understanding your soil is that one thing. Learning how your soil affects your plants will dramatically increase your odds of being a successful gardener.
Let’s take a look at the three steps you can take to get to know your soil better and get it ready for planting.
How to prepare your soil for planting
- Get a soil test
- Identify your soil texture
- Amend and fertilize your soil
Get a soil test
Getting a soil test is the secret to understanding your soil.
And understanding your soil can help you eliminate up to 80% of the problems in your garden. So don’t skip this step!
A soil test measures
- your garden’s pH
- level of organic matter
- nutrient levels
Identify your soil texture
Knowing what type of soil you have is a critical first step in choosing the right amendments for your soil.
And knowing your soil texture will help you better understand how to water your garden.
There are three main soil components of soil: clay, sand, and silt. Your soil test will give you a ratio of how much clay, sand, and silt your soil contains.
Clay: Clay soil feels sticky to the touch. Soils with high clay content have good water and nutrient holding abilities. But clay also restricts water and air movement.
- Clay soil particles are flat and small and stick together, so water and air can’t move between them easily. This also makes clay soils easy to compact.
- Because water doesn’t drain well through clay soil, it’s easy to over water it.
- You can also cause run-off by applying too much water too fast.
- A little clay goes a long way.
- Soils with as little as 20% clay particles behave like a sticky clay soil.
Sand: Sandy soils are the opposite of clayey soils.
- Sand particles are large and irregular shaped.
- So they have good spaces between them where air and water can travel.
- Sandy soils are great for succulents, cactus and other plants that need fast draining soil.
- Sandy soils need to be watered more frequently than clay soils.
- If you overwater a sandy soil all at once, the water will just flow away.
Silt: Silt is the third type of soil texture. Silt adds little to the overall character of your soil. It’s the stuff that settles out of slow-moving water and has a smooth, floury texture.
All three of these will be in your soil. The more even the ratio is between them, the more “loamy” your soil is. Loamy soils are the gold standard for vegetable and fruit growing. They are rich in nutrients and have good pore spaces that allow water and air to get to plant roots.
Most of the soil amending we do is to get our clayey, sandy or silty soils to behave more like a loamy soil with a neutral pH.
How to water your garden depends on what type of soil texture you have.
- Clay soils should be watered less frequently because they hold onto water longer.
- And sandy soils should be watered more frequently because they drain faster.
The best way to improve sandy or clayey soil is to add organic matter to it. Period.
Amending and fertilizing your soil
Before we get into the details of how to amend your soil, let’s cover a few things you should NOT do to your soil.
4 Things you should never do to your soil
- Fertilize or amend it (even with compost or manure) without getting a soil test first.
- Add sand to clay soil or clay to sandy soil.
- Work it when it’s too wet.
- Compact it.
Don’t make this common soil amendment mistake
Don’t try to turn clay soil sandy or sandy soil clayey. A soil that has a little as 20% clay will behave like a clay soil.
You won’t be able to add enough sand to clay soil to make a difference. If you try to, you’re doing soil replacement, not soil improvement. And adding sand to clay makes the soil more like concrete than soil.
The best way to improve sandy or clayey soil is to add organic matter to it. Period.
When and how to amend your soil
- Soil hydration is an important factor to consider when deciding which day you’ll amend your garden. Think like Goldilocks when picking the day. We want the soil to be moist but not too moist.
- You’ll either want to pick a day after you’ve just had rain. Or water the garden a day or two before amending it. You’ll need to give it time to drain. Never work your soil when it’s too wet.
- On the flip side, working it when it’s too dry can make it almost impossible to do if you have clayey soil.
How to work the soil
If your soil is compacted, very clayey, or very sandy, consider double-digging your garden bed.
- Double-digging isn’t necessary, but can drastically improve a problem garden bed in a short amount of time by incorporating organic material lower into the soil and creating air spaces where there are too few.
- Double-digging isn’t something you must do every year. Doing it once may be enough, especially if you refrain from re-compacting the soil.
- Too much turning over of the soil can break down the soil’s structure, and sets back the natural soil building processes that soil organisms have worked so hard to create. It also brings weed seeds to the surface, where they can germinate.
- But if your soil is a heavy clay that’s been compacted by machinery, or was excavated sub-soil, double-digging may be the only way to create soil structure where there is none.
That brings me to tilling the soil. If you have a problem soil (compacted, very clayey or very sandy) and you can’t double-dig it or hire someone to do it for you, a tiller is your only other option.
- The problem with tillers is that they create a hard-pan effect at the bottom of the blades that can exacerbate drainage problems in clayey soil.
- And, since you must walk behind the tiller, you’re compacting the soil as you go.
- So, if you use a tiller, use it once, and only till enough to incorporate the amendments into the soil. Don’t over-till your bed.
Your last option is to simply work the amendments into the soil with a garden fork.
- You won’t get them as deep into the soil as you could with double-digging, but it’ll be better for your soil than using a tiller.
- Over time soil organisms will work your amendments into the lower layers of soil.
- When using a fork, be careful not to step where you’ve loosened the soil.
Steps to take when amending your soil
Check your soil moisture level. Make sure it’s not too wet or too dry.
- Scoop some into your hand, and squeeze it.
- If the clump breaks apart easily but doesn’t crumble or turn to dust, it should be good to go.
- If it’s too dry, water it again and check it the next day.
- If it’s too wet, check it again tomorrow.
Spread your amendments and fertilizers evenly over the bed.
- Try to do this on a non-windy day.
- Wear a dust mask if you’re spreading dusty amendments.
- Incorporate them in by double-digging, using your garden fork or tilling.
- Lightly water the bed.
What is organic matter?
Organic matter in your soil is made up of castings from living organisms, plant roots, and residues from dead plants, animals, and soil organisms. These things are in various stages of decomposition. The most important type of organic matter is produced during the final stage of decomposition – when the organic matter turns into humus. (No, this isn’t the stuff you eat with Pita bread … that’s hummus!) Humus is a mix of stable, complex organic compounds that improve soil structure, water retention, and nutrient release to plants.
You may see bags in your garden center labeled “humus.” Most likely, this isn’t technically humus, but is really an aged compost. Humus takes quite a long time to form, so you won’t be able to run out and buy some.
Choosing what organic matter to add
If your soil is lacking organic matter, the best thing you can add to it is compost or green manure.
- Compost, composted manure, and green manure (aka cover crops) are the most common ways to add organic matter to your garden.
- Compost is plant material or animal waste, or a combination of the two broken down by microorganisms and some macro-organisms.
Growing green manure or “cover crops” is an excellent way to add organic matter to fallow vegetable beds. You can sow fast-growing crops like buckwheat in the summer, and longer growing crops in the fall.
Look at your soil test and follow the recommendations for how much organic matter to add this season.
- Don’t go overboard and add too much. More is not better.
- It’s possible to add too much compost or manure to your garden.
- Improving the organic content of your soil takes time. You can’t do it all in one season.
If you plan to use animal manure, make sure it’s well composted.
- Don’t add fresh manure to your garden except in the fall.
- Fresh manure takes several months to break down before it’s safe to use around plants, especially on vegetable crops.
Also, remember that manure and manure-based compost is salty. Adding too much can cause a salt overload in your soil. If salt shows up as a problem in your soil test, stay away from animal-based composts and manure.
Other amendments your soil may need
You may need to amend your soil’s pH levels or add specific nutrients or minerals. Your soil test will give you advice about what amendments you should add.
Understanding your soil can help you eliminate up to 80% of the problems in your garden. So don’t skip this step! Get to know your soil.