How to Amend Raised-Bed Garden Soil
Soil for Raised-Garden Beds
Before amending the soil of your raised bed, it's important to know what you already have in it. If you have followed so many that adhere to the square-foot gardening method, then you have a mixture of peat, compost, and a light material like vermiculite. If that describes your garden, great. If not, the point of an annual garden soil maintenance program is to get your soil to basically be an equal mix of three key ingredients. Let's take a look at this simple process.
How Often to Add Soil to Raised Beds
This process is one that you really only need to follow once per year. You will notice that the soil in a raised bed settles over time and requires new material. Whether you amend soil in fall or spring is really up to you, but there are some benefits to doing this job in fall so that new amendments can break down over the entire winter. This is especially true if you are adding homemade compost or chopped leaves from your yard, since they can work into the soil for several months and be turned over again in spring.
If spring is really the season that works best for you, it's OK. I add to my soil in spring and it works great, however I tend to use various types of compost from nurseries that are completely broken down.
Good Raised-Garden Bed Soil Mix
What you are really shooting for is soil made up of of equal parts peat moss, vermiculite, and compost. The peat moss retains moisture to use water well. The vermiculite prevents compaction, and the compost adds all kinds of good bacteria and nutrients that your plants need
If you are starting from scratch, use equal parts and add in roughly equal parts each year to keep that ratio. If, on the other hand, your garden is made from topsoil or whatever your natural soil is on your property, you might have to shake it up for a while. For example, you might really need a big dose of vermiculite and peat moss at first to lighten up your heavy soil.
Just keep adding as needed until your soil is light and won't compact. To give you some idea of what a perfect raised bed soil would look like once established, it would be somewhat brown in color from the peat and you would be able to push the soil down at any time since it will never be fully compact. In fact, each spring I can plant my seedlings without any tools at all since it is so easy to dig a quick hole in the soil with my bare hand.
Raised Bed Garden Soil Mix
Amend and Till Garden Soil
Once you have found the products needed, all that you need to do is add them to your garden and turn the soil. This is a much easier task in a raised bed that it is in a real garden so don't worry—this is not going to take long.
In an established garden bed I can amend the soil and turn the entire garden in less than 10 minutes. It is really easy, and since there is no heavy soil involved, it's no problem on the back either. In fact, I often use a 3-tine garden rake to just rake in the new amendments.
Once done, just smooth the soil and you'll be ready for planting.
Soil Amendment Alternatives
There are many things that you can add to your garden soil other than the core three ingredients, but that's really up to you. I can tell you that after many years of using the method described on this page that I have super results every year without fertilizer, so I'm sold.
Still, many people like to add things like crushed egg shells, coffee grounds, fireplace ashes, shredded leaves, or even grass clippings. Any of these can be a perfectly good amendment for garden soil, but my advice would be to be cautious of how much of any of these you add at a time.
Soil amendments like these can have a quick impact on soil qualities like calcium or alkalinity or acidity, for example. There are some vegetables that will like some of these amendments and others that will hate them. Still, in small quantities any should be OK. If you know what you'll be planting, do a bit of research first to make sure you won't be actually impairing the growth in you garden.
Remember, any natural amendments are probably OK in moderation, but I really don't think you can go wrong with peat moss, vermiculite, and general compost like composted manure.
Set Your Annual Plan
Now that you have a quick recipe for perfect raised bed garden soil, add this annual task to your gardening calendar. It only takes a moment, but the results are well worth it.