If you’re new to backyard gardening and are overwhelmed with all the soil options available, you’re not alone. Adding new soil to your already dirt-filled garden can feel like a pointless and expensive endeavor. That said, you may be wondering if adding another layer of soil is necessary or if your vegetables can grow solely on topsoil.
Vegetable plants can grow solely in topsoil if the topsoil has all the critical nutrients your vegetables need. Your soil needs to be fertile and healthy to facilitate growth. If the topsoil has an inadequate amount of nutrients, you’ll have difficulty growing anything.
Below, I’ll talk about what’s essential for growth in topsoil and how to know if your topsoil makes the mark. Then, I’ll talk about the importance of healthy soil and ways to get your soil up to par.
Do Vegetables Grow in Topsoil?
You may be thinking, “Wow, if vegetables could grow in topsoil, that would make things so much easier!” When you don’t have to make the extra effort to enhance your topsoil (on top of other tasks like digging in your garden, transferring your veggies, and sowing your seeds), it’s tempting to let your vegetables grow in topsoil and be done with it.
Vegetables do grow in topsoil as long as the topsoil includes all the needed nutrients and doesn’t have harmful substances. Critical nutrients for plants include nitrogen, phosphorus, and potassium. Some topsoil may have been exposed to lead or could be housing harmful bugs.
A good gardening mix includes one-third topsoil, one-third compost, and one-third of a different soil type — preferably something more sandy or coarse so your soil doesn’t become compacted. Luckily, you don’t need to fill your garden with bags of compost or new soil and blow your gardening budget in the process.
Also, you might be one of the lucky ones who have healthy topsoil to begin with. If you haven’t been growing your garden for very long, your topsoil may be healthy, fertile, and ready to provide nutrients to your plants and vegetables.
What Is Topsoil?
I’ve been talking about topsoil so far, but what is it exactly? Is it, as its name implies, the topmost layer of the soil in your gardening area? More importantly, can you buy it in a bag, or is it already there and only needs a few tweaks from you?
Topsoil is the dirt on the surface layer of your gardening area or lawn. It’s the naturally occurring soil that’s already there and native to your land. Technically, it doesn’t include mulches or composts.
In other words, the “starter” or “garden” soil you purchase at the gardening goods store doesn’t count as topsoil. This YouTube video explains the difference between the two:
What Your Plants Need To Grow
Plants need three things to grow: Water, sunlight, and healthy soil. Typically, people get the last one by grabbing a bag of gardening or starter soil from the store. For the more budget-conscious folks, compost or mulch can brighten up what they already have.
Your vegetables need 16 essential nutrients to grow. Whether this comes from topsoil, garden soil, or soil you’ve had in a bag in your garage for years (though unlikely), your plant should be ready to grow as long as those sixteen nutrients are present. The most important of them are:
- Carbon dioxide
Your plants can get hydrogen, oxygen, and carbon dioxide from water and their surroundings. If you remember your high school science class, water consists of a couple of hydrogen atoms and one oxygen atom.
Meanwhile, plants need carbon dioxide to kickstart the process of photosynthesis. Fortunately, they can get CO2 from places like — surprise, surprise! — the air humans breathe out. So yes, just breathing near your plant can boost their health.
The rest of the nutrients need to be present in the soil. Your topsoil may already include these 13 nutrients, though you’ll want to double-check before committing to the topsoil-only route. You can perform certain tests to check soil quality, which I’ll explain in a bit.
Nutrients in Topsoil
I’ve discussed why nutrients are essential to your topsoil. Sometimes, it’s what’s in your topsoil (rather than what’s missing) that’s the problem. Soils that have a lot of clay or naturally occurring peat moss are likely to get more compacted, which results in waterlogging and makes it challenging for your vegetable’s roots to grow.
Also, your naturally occurring soil can be downright dangerous sometimes. Some studies have found that topsoil can become contaminated with pollution or lead, especially in urban areas. Vegetables can still grow in that kind of soil, but the contaminants may ruin their quality.
If you want to figure out whether it’s safe to grow vegetables in your soil, you can have an environmental assessment study done. This assessment can also determine what nutrients are present and what types of soil are in your garden, so you can plan for things like compaction and waterlogging.
Not All Topsoil Is Made Equal
Some topsoils are nutrient-deficient, compacted, or home to fungi and predatory bugs. If these issues are minor, you can still grow vegetables in them. However, if your topsoil is too compacted to dig, won’t absorb water, or has lots of fungi and pests, you’ll need to either plant elsewhere or do something to improve the quality of your soil.
Bottom Line: Vegetables Can Grow Solely in Topsoil
If you’ve been growing in your garden for a long time, your soil has probably been sapped of all of its nutrients by the previous year’s crop. Your vegetables can theoretically grow in topsoil regardless of their quality. However, adding compost or mulch will ensure that your vegetables are getting the proper amount of nutrients. Besides, land can only stay fertile for so long.
What Kind of Soil Do My Vegetables Need?
If you’re new to gardening, you may think that all a plant needs are water, sunlight, and soil. That’s true, but only to a certain extent. Some types of soil work better for some plants than others. So what kind of soil is best for vegetables?
Your vegetables need loose, nutrient-rich soil with the right pH levels. Most vegetables and fruits can grow with a pH of around 6.8, but there are a few that prefer higher acid levels. Nutrient-rich soil ensures all vegetables have access to the 13 nutrients they need.
Again, it’s possible your topsoil already has everything required for healthy soil. But if that’s not the case, you can usually get suitable soil by mixing organic matter and other soils. You can combine gardening soil with your native soil, and adding in compost or mulch can boost your soil’s health further.
The Importance of pH and Nutrients
No matter what soil combination you use, your end result should be loose, non-compact soil that allows water to flow freely and plant roots to dig down deep. Also, the compost and mulch should support the 13 nutrients I previously mentioned.
The most essential plant nutrients have been previously listed. However, plants also need trace amounts of:
- Iron (promotes growth)
- Manganese (helps with photosynthesis)
- Copper (supports plant enzymes)
- Zinc (helps plant hormone with stem elongation and leaf growth)
- Boron (helps the formation of cells)
- Molybdenum (helps make nitrogen soluble)
Note that a nutrient-rich soil isn’t enough. If the soil’s pH isn’t compatible with the type of vegetable you’re growing, they can’t access the nutrients they need.
Fortunately, it’s possible to determine your soil’s pH levels beforehand. You can test soil pH levels using an at-home test, or you can send off soil samples to labs that specialize in testing them. You can also install a moisture meter in your garden.
Home pH Tests
There are a variety of home tests for soil. For example, test strips are some of the most straightforward and cost-effective options. The downside of some of the cheaper pH tests is that they’ll only tell you if your soil is acidic or alkaline, not their specific pH level. Some testing kits can also help you assess the nitrogen, potassium, or phosphorus levels in your soil. If you have wiggle room in your budget, you should opt for these.
Any mysteries in your garden can usually be solved with a good look at a moisture meter. Moisture meters detect sunlight, moisture, pH, humidity, and temperature. A high-quality one can be a lifesaver when it comes to letting you know what’s going on with your soil.
Vegetables can grow solely in topsoil, depending on how fertile and healthy your topsoil is. If your soil has lots of nutrients and tiny microorganisms that can help your veggies out, there’s a good chance your veggies won’t need much more. Otherwise, adding mulch or compost can help. You can also buy bags of nutrient-rich soil to blend with your topsoil.
To check how your topsoil is doing, use a soil test. Moisture meters also make for a handy tool when checking soil quality.