Some of the best fertilizer in the entire world is so simple to make. In fact, it’s likely being created under your feet right this minute such as earthworm castings. All over the planet, the humble earthworm is hard at work digging burrows and chewing through any material in their way. When pooped out, this digested dirt becomes one of the most beneficial forms of soil amendments in the entire world. And, garbage is what creates it!
Just one tablespoon of worm castings provide enough nutrients to keep a potted plant perfectly fed for two months. Additionally, similar benefits occur for outdoor plants. Best of all, worm castings are simple to make right at home with minimal equipment. With the proper setup, you can create high-quality garden fertilizer using nothing more than the trash you usually throw away.
What are Earthworm Castings?
As the excretions of earthworms, worm castings are what is left of garbage after worms have processed it. Often called ‘nature’s plow’, earthworms push their heads through the earth in order to create their burrows. When the soil is hard, worms move by eating their way through, creating some of the richest fertilizer known to man in the process.
Many nutrients in the soil aren’t available for plants to access until they have gone through the digestive system of worms. The acids in the stomachs of earthworms process common nutrients like nitrogen and phosphorus. Then, they pass them out of their body as small dark droppings (called castings) which make them easy for plants to access. As an earthworm can produce its body weight in worm castings every day, even a relatively small amount of worms can quickly provide you with an enormous amount of castings.
How Do Earthworm Castings Benefit the Soil and Crops?
Not only are worm castings an ideal form of plant fertilizer, they also work as a high-quality soil enhancer and compost starter. Best of all, worm castings are clean and odorless, making it easy to forget how they are actually made.
Unlike other forms of manure or artificial fertilizer, worm castings are immediately absorbed by plants and also enhance the water retention abilities of the soil they are placed in. Thus, helping your plants to better withstand the stress of drought and heat while also inhibiting the development of diseases like root rot. Castings are also gentle enough that they won’t burn plant roots with their high levels of nitrogen. This means that they can be applied directly to your plants without having to be aged first.
Worm castings are also loaded with beneficial microbes from the stomachs of worms that help to renew worn-out soils and create better habitats for soil bacteria. Even better, worm castings contain far fewer pathogens than regular topsoil because worms remove them during their feeding frenzies.
Because castings contain 50% more humus than regular topsoil, they are far more beneficial for plants. Worms also moderate pH levels and remove heavy metals from the soil when they produce castings. Thus, making the soil less damaging for young plants.
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Where Can You Get Earthworm Castings?
Though it’s simple to buy earthworm castings from most well-stocked garden stores, a cheaper option is to create your own in a personal worm bin. These bins can either be purchased pre-made or built from scratch from simple materials. The type of bin you decide to use depends on your price point and the number of worm castings you want to have available.
- Commercial Bin Systems: Pre-made bins typically contain several interlocking trays and are usually made from durable black plastic. They have mesh bottoms that allow liquid to drain through the layers into a collection system that creates a ‘worm tea’ that can be used to keep the system moist enough. The system works by allowing you to put food scraps in the top bins and stacking new bins on top as they fill. Over time, worms will process the bottom trays into castings, and after several weeks you can harvest these to use as a planting mix. Though commercial systems tend to be more expensive, they make producing worm castings extremely simple.
- Homemade Bins: For a cheaper DIY alternative, homemade worm bins can be created with plastic storage bins. Though quite a bit of work is needed up front to get these bins to drain as efficiently as commercial bins, they can be just as effective for making worm castings.
How to Harvest Earthworm Castings
Worm castings are ready to be harvested from worm bins when almost all the organic material that you added to the bin has been broken down and you can see plenty of small, dark pellets. To get the worms to leave the castings, take the lid off your worm bin and put the casting-filled bin on top. Sensing the sunlight, the worms will burrow down through the layers into the lower worm bins and leave the castings. After a few hours, you can harvest these castings and distribute them where you need them later using the tray to start a new feeding layer in your worm bin.
How To Use Earthworm Castings
Worm castings make a great addition to potting soil or seed starting material. Simply use about one part worm castings to two parts potting soil for a healthy mix. You can also use them to top dress existing plants every two to three months to keep your plants at peak health.
When adding castings to your garden, be sure to mix them into the top few inches of soil or at the bottom of planting holes when transplanting established vegetables or flowers. You can side dress your plants every few weeks throughout the growing season at a rate close to ½ every two months. There’s little reason to worry about over-applying, as worm castings are too gentle to burn the roots of your plants.
To make a compost tea, you can soak several tablespoons of worm castings in a gallon of water overnight. After soaking, strain and dilute this mixture and use it to revitalize your plants.
Note: It’s not a good idea to use the dark brown waste liquid from your worm bin (called leachate) as a compost tea because it tends to contain phytotoxins that can hurt your plants. Instead, this liquid should be reapplied back into the bin when it seems too dry.
Additional Tips for Using Earthworm Castings
If you want some extra tips for making the most out of your worm bin, you can follow these tips for success.
- Worm castings are especially effective when used for indoor seed starting. You’ll be sure to notice a big size difference in seedlings started with just potting soil and those grown with worm castings mixed in.
- To perk up brown, dying plant leaves, give them a few spritzes of compost tea to act as a foliar fertilizer.
- Because castings can be extremely expensive to buy in large quantities, it almost always makes sense to make your own instead. It’s the perfect way to use up your spoiled kitchen scraps! However, if you want to purchase them, we highly recommend purchasing them from here.