A Gardener's Secret to Success: Worm Castings
Have you ever noticed small piles of crumbly pellets in your garden or on your lawn, especially after a period of good rain? These are earthworm castings, the poop of our busiest and most beneficial soil aerators. Consider yourself lucky to see this on top of your soil.
Worm activity improves soil structure, aerates roots, and helps with water penetration. In addition, castings are slowly released, provide concentrated nutrients, and do wonders for plant health.
The Many Benefits of Worm Castings
Worm castings contain enzymes, beneficial bacteria, and humus.They contain no salt and cannot burn plants like steer or chicken manures. Worm castings, in a sense, moderate a plant's uptake of heavy metals as well as excess acidity or alkalinity from the soil. They provide an organic, water-soluble source of fertilizer that is rich in nitrogen, phosphorus, and potassium. In fact, the amount of potash is nearly 7x that found in regular fertilizers! This translates into dynamic root growth and plant structure. It is also a great source of calcium, magnesium, and other micro-nutrients that are key to overall vitality. Adding them to your vegetable garden will boost yields and help prevent blossom-end rot on tomatoes.
In comparative tests, the plants raised with worm castings grow larger with better root networks and depth, produce more fruits, and resist more fungal diseases. Worm castings have been shown to help retain soil moisture and inhibit verticillium wilt, a common disease of tomatoes.
Another impressive benefit is the way it naturally repels insects. The digestive system of earthworms produces an enzyme called chitinase. This enzyme is a degrader of chitin, the substance that comprises the exo-skeletons of most insects. When used properly, worm castings help to repel chewing and sucking insects like aphids, whiteflies, and hard-shelled plant bugs. If an insect feeds on the leaves of a plant that has absorbed the chitinase, its stomach will soon begin to dissolve, and death will come quickly.
How to Use Worm Castings
An application of worm castings should be about 1" thick and a foot or so in width. Spread it out away from the trunk and around the drip line of the tree or shrub then cover with a 2" layer of compost. Castings can also be mixed 1c per gallon of water as a brewed tea and applied as foliar spray.
In areas where soil is dusty and unable to absorb water, plants suffer because moisture never makes it to the roots. This hydrophobic soil is a challenge, and worm castings can help! Mixed in equal parts with topsoil and compost and worked into the existing soil twice a year in early spring and late fall, the improvement will be quite noticeable. Minimal tillage, plant variety, and mulch will all work with these amendments to produce great soil. Saving leaves and spreading them for a nice top dressing will also encourage worm activity and provide shelter for lizards, a great form of natural pest control.
Vermiculture is the raising of worms, and it is quickly becoming a widespread hobby due to the benefits of compost and castings. It is the red wiggler, Eisenia foetida, that is used for this purpose. Preferring organic matter over soil, they are voracious decomposers. Another is the African nightcrawler, Eudrilus eugeniae, which is a great waste consumer.
The common earthworm, Lumbricus terrestris, is the one we find while digging in our gardens. They burrow deeply and serve to aerate the soil where they prefer to live. They will not survive in compost piles, but they will still benefit your raised beds and garden plots.
All earthworms produce the mineral-rich castings which help to give the soil good texture for better roots and nutrient absorption.
Easy Do-It-Yourself Composting
Worms can be easily raised in a simple bin or a special worm habitat.
Things you'll need to get started:
- a plastic bin at least 2' x 2' and 1' deep
- a watering can or hose
- a small garden fork
- brown ingredients: newspaper, corrugated cardboard, coir, dried leaves, etc.
- green ingredients: fruit and veggie scraps, eggshells, coffee grounds, grass clippings, horse manure, etc.
- garden soil
- red wiggler worms
Avoid meat, dairy products, and oily things in any composter. They will smell bad and attract rodents and flies. It's easy to keep a small container near your kitchen sink for collecting the appropriate waste to add later. Grass clippings and yard waste should be free of disease and pesticide residue. Red wigglers are usually available in garden centers or can be ordered on-line. A good information source for composting is Worms Eat My Garbage by Mary Appelhof.
- To get started, drill 1/16" holes with 6" spacing on all sides of the bin, including the bottom. Worms like warmth and darkness and will stay to the center.
- Add 6" of brown ingredients like shredded newspaper. Loosely sprinkle garden soil on top.
- Add 3" of green ingredients like clean kitchen scraps and coffee grounds. Sparingly add more garden soil.
- Lightly water then thoroughly mix with the garden fork.
- Add red wiggler worms.
- It is important to keep the compost moist but never soggy. Think of a wrung-out sponge.
- Keep adding more brown and green waste as the worms eat it. Remember the 2:1 ratio.
- Turn the compost once every 1 to 2 weeks. When the waste becomes black and crumbly, you know it's ready.
The worms can eat 1/2 their body weight in one day! 2 lbs. of worms to a pound or more of compost is a good way to start. Worms can be removed by hand from the castings, or the castings can be sifted through coarse screens
Use Castings Early and Continuously
Earthworm castings are also available in most garden centers. Some varieties have added minerals and nutrients as well as increased levels of chitinase.
Whether you choose to buy the castings or raise worms yourself, adding them to your garden is the best thing you can do to improve soil, increase yields, and prevent both pests and disease. Don't wait until the insects become a problem; apply the worm castings at the time of planting. (1 part castings can be added to 3 parts soil for a suitable planting mix.) Throughout the year, add more for continued insect and disease prevention and vigorous growth. I recommend quarterly applications for active crops and bi-annual amendments for general improvement of soil structure. Happy harvest!
Questions & Answers
Is the tea better for existing potted hibiscus?
Probably. It would be easier for a container. Remember to water first, then apply any feedings.Helpful 5
Does worm tea hurt beneficial insects?
Worm tea should not harm beneficial insects. The chitinase in worm castings acts more like a repellent if sprayed on the leaves, and a soil drench would eventually give the plant a more systemic resistance. As with other plant sprays, remember to avoid the heat of the day. The benefits of worm castings for plant health are numerous. You can use it without fear.Helpful 1
© 2011 Catherine Tally