Help Your Raised Garden Bed Thrive With These Must-Know Soil Tips

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If the physical strain of weeding is keeping you from growing your own vegetables, you may find that a raised garden bed is a better than an in-ground one. Because it's elevated, less bending is required for removing dandelions and other invaders. A raised bed also gives you more control over the garden's growing conditions, including soil characteristics and water drainage. If you try one, choose high-quality soil to help your plants access vitamins, minerals, and water. 

Compost and topsoil are the building blocks of raised garden soil. Get the proportions right to set yourself up for success. About half of the bed should be filled with topsoil, whose weight and consistency are ideal for fledgling roots. The other half should be mostly compost, which increases soil fertility, introduces helpful microbes, and improves moisture retention. You can also include small amounts of substrate such as perlite, which helps air move through the soil, and sand, which discourages water from pooling. 

Consider amending your raised garden's soil with nutrient boosters, too. Before doing so, make sure you know exactly what your garden needs. Start by assessing which nutrients your soil is lacking. Testing the soil's nitrogen level to see if it needs fixing is an important part of this process. If it's low, you'll want to choose a fertilizer that can replenish it. Some nitrogen-loving plants –  peas and cucumbers, for instance — appreciate an additional nitrogen boost after flowering. Also determine if the soil's pH level is appropriate for your plants. Most vegetables like soil with a pH level between 6.0 and 7.0. Tomatoes and squash, however, prefer conditions that are a bit more acidic.

Once you've put together your raised bed, obtaining healthy topsoil and compost is your next order of business. When shopping, look for topsoil that's dark brown and breaks apart when nudged with a garden tool. Consider ordering it by the truckload from a bulk supplier or purchasing it by the bag at a garden center. If you're buying the bagged variety, you can choose a product that incorporates compost, fertilizer, or both. Combining a no-frills soil such as Michigan Peat 5540 Garden Magic topsoil with homemade compost can be cost effective. 

If you don't make your own compost, a soil-and-compost blend may fit the bill. One option is Coast of Maine Castine Blend organic and natural raised bed mix, which also contains worm castings to improve soil structure and kelp meal to boost micronutrient levels. Or amend basic topsoil with a product like Black Kow composted cow manure, which doubles as a slow-release fertilizer. No matter which soil blends you choose, confirm your bed's dimensions to figure out how much your garden needs. You'll want to fill the bed completely since the soil becomes more compact over time.

Working with a super-slim budget? You can reuse old potting soil in your raised bed. Before doing so, remove rocks, roots, and other debris, and microwave it in 2-pound batches to kill harmful microorganisms. Each batch needs to be zapped at full power for a minute and a half. If possible, mix this reused soil with fresh topsoil. This helps replenish beneficial microbes the microwave has zapped in your recycled soil. Also restore its nutrient levels by amending it with fertilizer.

If your soil needs fertilizer or other amendments, add them after assessing which nutrients are needed but before sowing seeds or planting seedlings. A soil testing kit can help you choose the right add-ins. The Pawfly 4-in-1 soil test kit checks the soil's pH level as well as its nitrogen, phosphorous, and potassium content. Pair a tool like this with research about the nutrients and pH level your plants need. If your soil is too alkaline, it may benefit from a pH-lowering product such as gypsum or ground sulfur. If it's too acidic, ground limestone can help.

One of the most popular types of fertilizer on the market, NPK, upgrades your soil with balanced proportions of nitrogen, phosphorous, and potassium. It's especially helpful for squash, peppers, and other plants that extract significant amounts of these nutrients. As the growing season progresses, these heavy feeders may need additional servings of fertilizer. The nitrogen helps leaves form, the phosphorous aids root formation, and the potassium bolsters plants' defenses against disease and extreme weather. Opt for granular formulations while your plants are young and tender. 

Sometimes plants need nutrients that standard NPK fertilizer doesn't contain. For instance, adding calcium to your soil can help tomatoes fend off blossom end rot. A calcium-containing product such as Miracle-Gro Shake 'N Feed Fruit and Vegetable Plant Food can meet your needs, but don't rule out natural remedies. Eggshells are an unexpected treat for many garden plants. When ground up, they can enrich the soil with calcium.