What is the best soil for a vegetable garden? Soil is very important because it is the environment where your crops will live.
This means it needs support their needs and allow them to absorb moisture and nutrients to grow.
In this article, I’ll explain the best kind of soil for your vegetable garden whether you are growing it in the garden, on a raised bed or in containers.
In your garden, your plants live in the soil. As such, it not only provides them with the foundation to stand upright, but also supplies them with many of their needs. These include:
- Moisture (water)
- Air (oxygen and carbon dioxide)
It’s also worth noting that your garden (or yard) will be made up of a combination of soils, not just one kind. And, different sections may have varying compositions as well, especially if you have a big plot.
And contrary to what your eyes may lead you to believe, only about 50% of soil is solid material. The rest is made up of air and water.
Types of Soil
When it comes to gardening there are 6 basic types of soil. These are clay, silt, sand, loam, chalk and peat. Each of them has their own pros and cons.
Unfortunately, in most cases, you won’t be able to decide what kind of soil your home comes with. The good news is, with a little work, you’ll be able to improve the quality of your garden’s soil.
- Clay Soil. Clay soil is characterized by particles that are smaller than 0.002mm. You’re likely familiar with it because it is what people use for pottery. That said, it is heavy. This makes it hard to grow with. But, it’s not all bad. Clay retains moisture better than sandy soil. It also holds certain minerals quite well.
- Silt Soil. Silt has slightly larger particles compared to clay at about 0.002mm up to as big as 0.05mm. It is smooth to the touch and does a good job in retaining water and nutrients. Unfortunately, it can be prone to compacting. This prevents your plant’s roots from extending outwards as much as they should. It also makes it hard for air and oxygen to penetrate the soil.
- Sandy Soil. You’re probably most familiar with sand. It’s what you see on the beach. And, has a coarse texture. Sand particles run between 0.05mm to 2.0mm in size. They don’t hold well together which makes them unstable for your plants. Water, erosion and inclines can all move them. Sand also doesn’t retain water.
- Loamy Soil. Loam is the combination of clay, silt, and sand, in different amounts. As such, you’ll see variations of it depending on which kind of soil dominates the combination. That said, loamy soil is ideal for gardening. But, it’s also rare to find it in any backyard.
- Chalky Soil. Chalky soil is often fertile as it contains a good amount of organic matter. But, it is alkaline in nature (with pH between 7.1 to 10). Also, it’s somewhat stony and will dry out quite quickly. As such, you will likely need to modify its pH and water your garden more frequently.
- Peat Soil. Peat soil contains high amounts of organic matter and it retains water well. Unlike chalky soil, peat soil is acidic in nature. Thus, it’s ideal for plants that like acidic environments.
The good news is you’ll likely be able to work with whatever kind of soil your yard has. The question is how much work will you need to do to get it to the condition that allows you your garden to produce optimum yield.
The best way to do so it via a soil test. The results will give you an idea of what you have. This allows you to take proper action to improve it.
In addition to the kind of soil your yard or garden has, it’s just as important to understand that it also contains nutrients that your plants need. The more fertile your soil is, the less fertilizer you’ll need.
Where Do Soil Nutrients Come From?
- Organic matter like dead plants and animal waste that breaks down
- The atmosphere
- Weathering of minerals and rocks
- Chemical reactions in the soil
On your part, you also contribute to its nutrient content by adding fertilizer and compost.
It’s important to stress your part in this because your plants take up a lot of minerals from the soil. As such, you don’t only need to supplement it with the nutrients it doesn’t have but also replaces those nutrients for the next season’s crops.
When it comes to the minerals that plants need, they’re divided into a few groups. These groups are classified based on how much of those nutrients they need.
These are the 3 minerals you’ll see in the labels of fertilizer containers. They’re the 3 big numbers that look something like this: 10-10-10 or 5-5-5.
That number is referred to as the N-P-K ratio or the Fertilizer Grade. And, it tells you how much of each of the 3 minerals (in percentage) is present in that particular fertilizer formulation.
The reason those 3 numbers are listed is that they’re the most important nutrients for plant growth. By that I mean, they’re the minerals your plants need in the largest amounts.
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
It’s also worth noting that 3 other major nutrients are often left out. These aren’t mentioned because they’re assumed to be understood.
In part, that’s because you don’t have to buy or apply them. Instead, they’re readily available in the air and water. But, you have to make them accessible by making the soil loose and aerated.
Here’s a chart of the essential nutrients or macronutrients plants and vegetables need.
It includes the function of each nutrient, signs of deficiency and signs of excess.
After your primary or major nutrients, you have the secondary nutrients. Your plants also need a lot of these. But, not as much in volume as they do the primary ones.
These secondary nutrients are:
Micronutrients are minerals that your plants need in trace or minute amounts. Thus, they need only very little of them.
That said, they still need them. Otherwise, you’ll see some unpleasant things happen to your vegetables when one deficiency or another happens.
Plant micronutrients include:
This chart shows you the different micronutrients plants and vegetables need, including the secondary nutrients.
For each nutrient, the chart shows the function, signs of deficiency and signs of excess.
How Do Plants Absorb Nutrients?
One of the most important things to understand about plant growth and the nutrients the drive it are availability and absorption.
Just because you’ve provided your garden soil with all the nutrients they need, it doesn’t necessarily mean that your plants will benefit from them.
- Nutrients need to be broken down into cations (positively charged ions) and anions (negatively charged ions) before they can be used by your plants. As such, dead leaves or grass clippings in their physical form aren’t helpful. At least, not until they’re broken down into their ionic forms.
- Minerals that aren’t in their proper forms can’t be absorbed by plants
This is why gardening is more than just about feeding your plants fertilizer.
The availability of nutrients in the soil to your plants is affected by a lot of things. These include:
- How big their particles are
- Amount of humus or organic matter there is in the soil
- Your soil’s pH level (which changes the form of the nutrient in the soil). We’ll discuss more in the next section.
- Aeration or how much air they get
- Water content
- The surface area coverage of your plants’ roots
- And a few more factors
That said, plants absorb their nutrients through their roots, much like they do water.
While the root tips do a lot of the actual work, it also gets a lot of help from a few unexpected friends. These are:
- Microorganisms in the soil. These microbes break down the organic materials so that plants can absorb them (mineralization). Additionally, they also help hold nutrients for your plants while protecting it from stress. So, in return, interestingly enough, your plants actually make food for them. In fact, it uses up to 30% of the energy supplied to its roots to feed these microorganisms.
- Fungi supply your plants’ roots with nutrients including phosphorus and nitrogen. In part, it does so by increasing the size of the roots and allowing for more contact for the roots with soil.
This is why taking care of the soil, including the organisms in it is so important for you as a gardener.
That said, it’s during photosynthesis, which occurs in the leaves where your plants create the fuel they use for energy is made.
This reminds you very much of how your body works. You eat and drink with your mouth. But, the actual absorption of nutrients happens in your digestive system (stomach and intestines).
In any case, this means that plants need to transport the water and nutrients absorbed from the roots all the way up through the stem for this to happen.
The only exception to this is carbon which it gets from the air. And, it does so through the pores on its leaves (stomata).
Here’s a reference chart that shows you fertilizer and nutrient requirements of different vegetables.
It will show you which vegetables are heavy feeders, light feeders and soil builders.
Soil pH Levels
We touched on soil pH a bit in the previous section.
Now, it’s time to understand it better.
One of the first basic steps in analyzing your soil is to test for its pH. And, if it isn’t in the proper range, you’ll need to take action to adjust it.
Here’s a chart of the different vegetables and their ideal soil pH levels for optimal growth.
Why is Soil pH Important?
The pH scale is a system that’s used to measure the acidity or alkalinity of a substance. It runs from 0 to 14, with the middle 7.0 being neutral, i.e. not acid, not base (alkaline).
- Any value below 7.0 is considered acidic. The lower it is, the more acidic the substance is.
- Values above 7.0 are considered alkaline. And, the higher up you go, the more alkaline it gets.
Most garden soils fall within the 4.5 to 7.5 range. Although, some reach either extreme.
More importantly, the majority of the crops in your vegetable garden grow best when the soil pH is around 6.5 or so.
As such, this is the pH value you’ll likely end up trying to achieve.
More importantly, your soil’s pH affects the availability of nutrients in the soil to your plant. That means that pH that’s too high or too low affects how your plants can use those minerals regardless of how abundant it is in the soil.
Here’s a chart that shows you the availability of different nutrients at different pH levels. If you noticed, the largest blocks (most availability) happens in the middle sections (pH of between 6.0 and 7.0).
When soil pH is too low (i.e. too acidic):
- Nutrients like phosphorus become less available. Considering that it’s one of the 3 major nutrients, you can expect it to significantly affect the growth of your crops, especially flowering crops since phosphorus promotes flowering.
- Some elements like manganese and aluminum become toxic.
- The amount of beneficial soil bacteria decreases since the conditions aren’t favorable to them
When soil pH is too high (i.e. too alkaline):
- Nutrients like zinc, iron, manganese and copper are not readily absorbed by your plants.
- The supply of water to the roots gets restricted
If you prefer the combined chart of how to adjust soil pH using sulfur and limestone, here it is.
One of the most important aspects of your soil is its ability to drain well.
As a beginner gardener, one of the things that you’ll probably have a hard time wrapping your brain around is the irony of soil.
- On one end, you want soil that’s good in retaining water (and nutrients)
- But, you also want soil that drains well
What’s up with that?
Well, it’s because your plants’ roots need water.
- Water keeps the root healthy. It also prevents your plants from wilting. And, it allows them to make their own “food”, via photosynthesis, among many other things.
- Too much water retention prevents air from getting in. That’s because an abundance of water in the soil blocks all the extra spaces between the soil particles. This prevents air from getting in. Just as much as your plants need water, it also needs air (oxygen) to survive and grow. Just as importantly, waterlogged soil increases the risk of root rot.
As such, you want soil that does both. That is, retain enough moisture to keep your plants hydrated. But, not too much that it gets waterlogged.
A good analogy of this is your body. Without water, you get thirsty then dehydrated. The latter comes with a host of health problems if you don’t address it.
But, if you drink too much water you get bloated and retain fluids, which not only doesn’t look good but also makes you feel lousy.
What Causes Poor Soil Drainage?
- Infertile topsoil. This can happen if the soil wasn’t cultivated. Similarly, a low amount of organic matter (humus) can also cause this.
- Presence of a pan. Soil pans are dense layers of soil. They’re often 1-2 inches thick. Pans can form when there’s an abundance of certain minerals that can bind with soil particles. Other times, hard pans are man-made, be it from heavy foot traffic or repeating plowing.
- Location. Sometimes the land you’re on or the surrounding area just isn’t suited for draining. Or, they’re high water tables.
How to Check Your Soil’s Drainage
One of the easiest ways to tell if your soil isn’t draining water is to look at its surface after it rains. If there are puddles of water on or around your plants or the soil itself, it’s not a good sign.
Similarly, if you notice that perennials aren’t growing as they should. Instead, it’s the water-loving plants like moss that are thriving, that’s another sign of poor drainage.
If you don’t want to wait for the rain. Or, are likely to forget after it rains, here’s another way to check to see how well your soil drains moisture.
- Dig a hole about 8-10 inches deep
- Fill it with water
- The water will drain. Then fill it again the next day.
- In the second filling, time how long it takes for the water to drain
- Ideally it (2nd filling) should drain in under 8 hours.
- If it lasts more than that, you need to improve your soil (for example, adding compost)
That said, soil that drains too fast is just as bad as soil that drains too slowly. In this case, you’ll need to keep watering your plants more frequently than normal.
Either way, improving the organic matter in your soil (like by adding compost) is a good way to fix these issues.
Alternatively, an even worse situation would be rocky soil. Soil with lots of big rocks is a lot more difficult to remedy than amending slow draining soil (like clay) or soil that drains too well (sandy soil).
In this case, you may want to consider
- Container Gardening. This allows you to use your own “soil”. With potting mixes, you’ll be able to better control the quality of your soil.
- Raised beds. If you want to grow on your garden (and not containers) but have poor soil, you can set up raised beds. That way, you can add in your own soil that’s different from the one in the ground.
Both methods are effective because you essentially “replace” your garden soil with much better quality material.
While mulch is not necessary for vegetable gardens, it can be helpful depending on the kind of vegetables you have and the weather.
Below is a chart of the different types of mulch and their pros and cons.