5 Tips for Improving Your Raised Bed Garden Soil
Wondering how often, or even better yet, how do you improve the soil in raised beds? You are officially convinced on the benefits of raised garden beds and maybe you've been gardening in raised beds for years.
Whether you are new to raised bed gardening or you're a raised bed gardening pro, we’ve got some gardening tips below on raised bed soil maintenance. Raised beds, in a way, are like large containers. If you deplete the soil nutrients over the course of one or more gardening seasons, you need to rebuild it. Sure, organic fertilizers are great to add in the spring. But, they are not the complete answer in improving your soil quality.
By properly maintain your soil in the raised beds, you won't need to replace it every few years. In fact, unless your plants bring in a soil-borne disease, you don’t need to replace your raised bed soil at all -- just continue to maintain it! And what do you do to maintain healthy soil in raised beds? Here are some tips:
1. Add Compost
Compost just isn’t for spring bed preparation! Add compost to your raised beds in the fall. In raised beds, compost is a great way to end the gardening season. Since this compost will sit on the bed all winter, it does not have to be completely broken down. The composting process can actually occur on the raised bed. Besides, it’s a great way to clean up the yard from fall yard wastes. Spread a couple of inches of compost on the bed, and then cover with mulch. The mulch will protect the soil from harsh winter weather, keeping the nutrients in the raised bed.
2. Use Soil Amendments
Soil amendments are mixed with soil to improve soil quality in raised beds. As to specifically what soil amendments do to the soil will depend on what kind of soil amendment you are using. You might want to consider using soil amendments to increase the soil’s nutrients or to change the soil’s physical structure, often called tilth. Simply put it’s basically the texture of the soil. Let’s say, for an example, your soil in your raised bed is drying out too fast. Or, maybe you didn’t use the right soil mixture in the first place. Possibly your soil had too much sand in it, making water drain quickly through the soil before the plants have a chance to absorb it.
You can correct the soil by adding a soil amendment, like compost, rich in organic matter. The organic matter will retain moisture in the soil. On the flip side, if the soil is retaining too much water, you can mix greensand with the soil, which helps water drain more efficiently.
Here’s a list of organic soil amendments you might want to look into to improve your raised bed soil quality: vermiculite (worm castings), compost, coir, greensand, grass clippings, cornmeal, alfalfa meal, lava sand, straw and kelp meal.
3. Plant a Cover Crop
When thinking about replenishing nutrients in raised beds, don’t forget about cover crops. Cover crops aren’t just for large scale farmers looking for weed suppression. They will benefit raised beds for the backyard gardener, too.
Cover crops aerate the soil, especially if you plant a cover crop with a deep root system like alfalfa. The root system will pull nutrients deep in the soil to the surface, which will make nutrients readily available when it comes to planting time. A few weeks before planting time, till the cover crop into the soil. This increases organic matter, building healthier soil and increasing nutrients.
If you want to add nitrogen to the soil, consider planting legumes as a cover crop. Examples of legume cover crops are alfalfa, fava beans, and crimson clover. After you’ve closed the raised bed after the growing season, try winter cover crops to protect and aerate your raised bed soil, as well as, add nutrients. Here’s more information on cover crops, including a cover crop chart.
4. Try Lasagna Gardening
Lasagna gardening, sometimes called No Till gardening or sheet composting, is another great tip for improving soil conditions, and it’s also a fantastic way to create a raised bed. So, whether you’re looking to start from scratch or work on an existing raised bed garden, you can improve your soil conditions from the get go. As your soil is gets depleted in your raised bed over time, you keep adding layers like you would in a lasagna garden, by sheet composting, and completely renovate your soil from the top down.
Here’s another great resource for lasagna gardening complete with pictures of constructing a raised bed with the lasagna gardening method. Keep in mind, if you renovate your raised bed soil with this method, you will need at least six months for the layers to break down to plant.
This method works very well if you are rotating beds, or grow only one garden season. But, this resource from the link above, gives a great tip if you want to start sooner. If you want to plant right away, just spread two or three inches of compost or soil as your top layer to plant directly into the bed. Then you can start immediately!
5. Prepare Raised Beds for the Winter
Don’t forget the end of the garden season is a great time for a just a few simple steps for soil maintenance. It’s kind of like closing up shop for the winter. That is, if you aren't in an area of the country where you can grow year round.
Here are two great tips to prepare your raised beds for the winter: Leave the roots. Don’t pull out the plant! Just cut the plant at the soil surface. The roots will decompose and aerate the soil. Spread a few inches of compost over the bed, and cover with mulch. The mulch protects the soil over the winter conditions, while the compost adds nutrients over the winter. (Or, you can skip the compost and mulch and plant a cover crop.) For more information, check out our article on winter gardening checklist tips.
If you were thinking about hauling off the dirt from your raised bed and replacing it all with brand new soil, try these 5 tips to improve soil quality in a raised bed instead and save yourself the trouble. It’s much, much easier than getting rid of what you have and starting again from scratch. And it's also extremely effective at improving your soil quality.