Garden

The Benefits of Worm Casts

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Credit: Viorika/iStockphoto

Earthworms are very important to decomposition processes that occur naturally with dead organic matter. Without earthworms, it would take a long time for bacteria and fungi alone to convert this matter into usable plant nutrients. Worm casting (a.k.a. vermicomposting) is the entire process of recreating natural worm decomposition in a streamlined form, producing nutrient-filled worm excrement (a.k.a. casts or vermicompost). Worm casts are several times richer in inorganic material, such as phosphates and nitrogen, than topsoil. Also, beneficial bacteria in the worm’s digestive tract, which enhance organic decomposition, have been found in much higher amounts in the ejected worm casts than in organic material that hasn’t been ingested. Since an earthworm can produce its own weight in casts within 24 hours, worm casts are one of the most efficient and nutritious fertilizers currently known. Worm casting improves decomposition by creating the best suitable environment for worms and bacteria to break down organic material. Here are a few factors that can affect the quality of your vermicompost:

  • Temperature – Worms prefer a cooler climate (12-21°C) for composting. The soil should not reach below freezing or above 32°C, as these extreme temperatures may kill the worms.
  • pH – Worms prefer slightly alkaline soils. Adding calcium carbonate, or “garden lime” can help the soil reach the right pH. Be careful not to use the similarly named calcium oxide, as this will increase the alkalinity to toxic levels for the worms.
  • Aeration – Worms require large amounts of oxygen for proper breakdown of organic material. You can add holes to your bin, or use a continuous flow-bin, and regularly remove the composted material from your container. If there isn’t enough oxygen in your compost, it will begin to stink and become toxic for the worms.
  • Food – The best carbon-nitrogen ratio for your worms is 30:1, so make sure that the food mix is more “brown matter” i.e. wood and shredded papers, than “green matter” which includes grass and food scraps. Make sure that you don’t add items with pesticides into your compost since the toxins will kill your worms. Also, avoid adding sticky products such as food labels, items with high proteins and fats such as meats and bones, and compostable cutlery.
  • Moisture – The right amount of moisture, ideally like that of a wrung-out sponge, will make it easier for your worms to break down the food. Avoid adding high-water-content materials such as watermelon, which has almost no nutrients for worms and would also disrupt the water balance of your soil.

If you follow the above guidelines for producing good compost, you and the worms should be very happy gardening together.