top of page
Search

Key Facts about Vermicast

The end-product of vermicomposting is called vermicast/casting – and it's essentially worm poop. Here are the key things to know about why it's so good.


What does vermicast contain?

Across multiple analyses, well-finished vermicompost typically contains roughly:

  • N: ~0.6–2.5%

  • P: ~0.13–1.7%

  • K: ~0.4–2.5%


The exact numbers depend a lot on feedstock (manure vs crop residues etc.), but most studies agree it’s richer in available NPK than traditional farmyard manure or thermophilic compost.


It also consistently contains:

  • High organic carbon and humic substances

  • Micronutrients (Ca, Mg, S, Fe, Zn, Cu, Mn, B)

  • Beneficial microbes (N fixers, P-solubilisers, decomposers) and plant-growth regulators (auxin- and gibberellin-like compounds)

These combined chemical and biological properties are the main reason vermicast often outperforms conventional compost at much lower doses.


Effect on plant growth and yield

A global meta-analysis of vermicompost effects on crops (pot and field experiments) found average increases of:

  • +26% commercial yield

  • +13% total biomass

  • +78% shoot biomass

  • +57% root biomass


Key points from that analysis and later reviews tell us that:

  • Growth/yield responses were strongest when vermicompost made up 30–50% of the potting medium volume in controlled experiments.

  • Cattle manure–based vermicompost often gave the biggest yield boost in comparative trials.

  • A 2022–2024 wave of reviews conclude that vermicompost consistently improves growth and yield of cereals, pulses, vegetables, fruits and ornamentals, especially when combined with mineral fertilizers rather than replacing them 100%.


For vegetable crops specifically, a review reports:

  • Tomato yield increases up to ~70% at 15 t/ha vermicompost vs control, with higher leaf area and nutrient content (K, P, Fe, Zn).


Soil health benefits

Recent reviews and field studies show vermicompost improves soil on several fronts.


Physical:

  • Better aggregate stability, porosity and water-holding capacity, especially in degraded or acidic soils.

Chemical:

  • Increased CEC (cation exchance capacity) and nutrient availability (N, P, K, Ca, Mg), partly via humic substances and organic acids.

  • Slow-release behaviour: nutrients are retained longer and released more gradually than from mineral fertilizers.

Biological:

  • Higher microbial biomass, activity and diversity, including beneficial bacteria and fungi.

  • Enhanced enzyme activities linked to nutrient cycling (phosphatases, dehydrogenase etc.).


Overall message from several 2022–2024 reviews: vermicompost functions both as a fertilizer and a soil conditioner, and can help rebuild soil quality in systems with long-term synthetic fertilizer use or erosion.


Disease and pest suppression

There’s a surprisingly strong body of work showing vermicast and its extracts (vermicompost tea/vermiwash) can suppress diseases and some pests:

  • Solid vermicompost and teas reduce incidence/severity of pathogens like Pythium, Phytophthora, Fusarium, Rhizoctonia and Verticillium in greenhouse and field trials.

  • Mechanisms identified in reviews:

    • Competition and antibiosis from diverse beneficial microbes

    • Hyperparasitism/predation (e.g. antagonistic fungi, predatory nematodes)

    • Induced systemic resistance in plants (ISR-like responses).


A review on vermicompost & vermiwash concludes that these products can reduce reliance on chemical fungicides and insecticides, particularly in high-value crops, if quality and application methods are well controlled.


Practical caveats & research gaps

Studies and reviews flag a few important caveats:

  • Huge variability in product quality (feedstock, worm species, process control) → nutrient contents and disease-suppression effects are not uniform.

  • Very high substitution rates in pot trials (e.g. >50% vermicompost in the medium) can sometimes reduce germination even if later growth is strong – likely due to high salts or excessive biological activity near seeds.

  • For large-scale arable systems, economics and logistics (bulky material, transport) are still a constraint; more work is ongoing on concentrates and extracts to keep application rates tiny.


Sources

Join our mailing list – we'll occasionally send you updates on our projects and latest news!

Privacy Policy

INVENIRE LOGOT 2025.png

​doorbell[at]invenire.fi​

+358 40 8228 848​

Kokkilantie 835, 25230 ANGELNIEMI, FINLAND

  • LinkedIn
  • Youtube
bottom of page