The type of soil needed for planting garden beds is usually a mixture of 60% topsoil, 30% compost, and 10% potting soil (containing perlite, peat moss, and/or vermiculite). Some people also add organic fertilizers. The depth of this soil depends on what you plan to plant in it.
A good, healthy soil mixture promotes the natural ecosystem in which plants will thrive, which is essential for raised bed gardening. If you want to know about this combination and some other suggestions,
How Much Soil Do I Need For My Raised Garden Bed?
First, since you are purchasing one or more beds, you may need to purchase soil in bulk. It's much cheaper, you can always mix it at home, and mix it up later if you have extra. After all, there's always something to settle for.
You can usually find pre-prepared compost in bulk as well. If you want a good price on compost and mulch, check with your local landfill and waste management companies. Maybe your municipal waste removal department has leaders. In our area, landfills in local towns are sold by the cubic foot, usually half the price you'd pay elsewhere.
When buying soil in bulk, use cubic feet or cubic yards. That means you need to break out of high school math again! Remember that when it comes to standard raised garden beds, you are dealing with a rectangle.
Remember how to get the area of a rectangle? One side x other side = area²
Example: 4 feet x 6 feet = 24 feet²
You do this, then multiply that area by the depth of the space you need to fill. Remember, we use feet as the unit of measurement. So when you measure inches, you need to divide it by 12 (because there are 12 inches in a foot).
Example: We have a taller bed so I need to put 24 inches of soil on it.
24 inches ÷ 12 = 2 feet Now 24 feet² x 2 feet = 48 feet³ or 48 cubic feet.
If you need to change this to cubic yards, remember that 27 cubic feet = 1 cubic yard. So you need to divide the cubic feet figure by 27.
Example: 48 cubic feet ÷ 27 = 1.78 cubic yards
do you know?
Sometimes topsoil mixed specifically for plants is called loam. Loam soil is soil made up of a balance of three main soil types: sand, silt, and clay. Since this combination of soil types is known to retain the proper amount of moisture, oxygen and nutrients, it creates the perfect soil texture for plant growth.
What is the best soil recipe for raised garden beds?
60% topsoil/loam
30% compost
10% potting soil (you want a potting soil mix that contains perlite, peat moss, and/or vermiculite)
Keep in mind that these percentages are approximate, but I've searched many extension service publications and gardening websites to find this, and the percentages tend to stay around this. I'm going to use it in my own bed and see what happens.
If you want to add fertilizer to this mix, just add ½ cup per 5 square feet of soil.
What do I need to know about your soil?
In some places, high-quality topsoil may not be available. If this is the case, then you may need to use an alternative. Throwing out 50%-50% of your compost and potting soil mix can replace it. Or, if you have some topsoil but a limited amount, you can always mix it in with a 50%–50% mix to give it a new look.
Speaking of fresh soil—you can absolutely refresh old soil. When I transplant other plants from one place to another, I tend to find old soil. Also, the soil in the raised bed will settle with the seasons and then the soil volume will decrease as the various plants are removed.
When I find old soil, I pour it over the bed I want to replenish. Then, I grab enough new potting soil to fill the beds to my liking. I use a yard rake on the shorter/larger beds and a hand tool on the higher beds to mix all this soil together.
You can also add peat moss to raised beds. However, it should not exceed 20% of the total portfolio. Why? Because peat moss is naturally acidic. So you probably don't want to grow vegetables in it.
The purpose of raised beds is to help reduce gardening work by limiting weeding and providing your bed with the best, most fertile soil possible. So don't trample or compact the soil! The loose, well-drained soil you can develop is a huge advantage and allows your plants to thrive. If you compact it, you reduce aeration and slow down the activity of earthworms and beneficial microbes below the soil surface.
You can add a mulch of fine wood chips to the top of the soil for better moisture retention. When wood chips decompose naturally, they add more nutrients and volume to the soil.
