The worms ingest organic matter, fragmenting and grinding it into reusable worm castings, which is high in Nitrogen, Potassium, Calcium and trace elements. These nutrients are why Vermicast can be used as a natural fertilizer in gardens, pot plants, hydroponics and vineyards.

Vermicasting, also called vermicomposting, is the processing of organic wastes through compost worms. It is a natural, odourless, aerobic process, much different from traditional composting. Compost worms ingest waste then excrete casts – dark, odourless, nutrient- and organically rich, soil mud granules that make an excellent soil conditioner. Compost worm casts are a ready-to-use fertiliser that can be used at a higher rate of application than compost, since nutrients are released at rates that growing plants prefer.

Vermicasting can be done on a small scale by homeowners with household organic wastes, on a large-scale by farmers with manure or by the food industry using organic wastes such as fruit and vegetable cull materials. Through proper design, vermicasting is a method of waste handling that:

  • is clean, socially acceptable, with little to no odour
  • requires no energy input for aeration
  • reduces the mass of waste by 30%
  • produces a valuable vermicast bi-product
  • even generates worms as fishing bait

Important Facts About Vermicasting

  • Turning organic wastes into casts takes approx 22–32 days, depending on density of waste and worm maturity (regular composting requires 30–40 days, followed by 3–4 months curing).
  • Vermicast does not need curing, but fresh casts undergo 2 weeks of nitrification where ammonium transforms to nitrate, a form that plants can uptake.
  • Use organic materials that meet the worm's feed preferences, including a material density of 350–650 grams/Litre.
  • Worms should not be crowded, so the ideal stocking density is 150 worms/Litre of wastes.
  • worms ingest about 75% of their body weight/day; a 0.2 g worm eats about 0.15 g/day.
  • If you discover worms trying to escape any system, it is a good indication that something is wrong with their feed or environment
  • Earthworms should be allowed about 1 week to migrate from finished vermicast to fresh waste.

Vermicast nutrient content varies with earthworm feed type, but feeding waste to earthworms does cause nitrogen mineralization, followed by phosphorous and sulphur mineralization after egestion. A typical nutrient analysis of casts is C:N ratio 12–15:1; 1.5%–2.5% N, 1.25%–2.25% P2O5 and 1%–2%, K2O at 75%–80% moisture content. The slow-release granules structure of earthworm casts allows nutrients to be released relatively slowly in sync with plant needs.

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