Clearing the Confusion: Nutrient Values in Worm Castings vs. Worm Juice Extracts

Clearing the Confusion: Nutrient Values in Worm Castings vs. Worm Juice Extracts

For Australian farmers managing broadacre crops, pastures, or horticulture, optimising soil health and, in particular, nutrient delivery is critical to boosting yields and maintaining sustainable operations. At Worms Downunder, we often get questions about the differences between worm castings (vermicompost) and worm cast extracts, like our Worm Brew. There’s some confusion around their nutrient profiles and how they fit into large-scale farming. Let’s dive into the science to clarify their roles, ensuring you can make informed choices for soil programs. 

Worm Castings: A Nutrient Powerhouse for Soil

Worm castings are the nutrient-rich byproduct of earthworms breaking down organic matter. They’re loaded with essential macronutrients like nitrogen, phosphorus, and potassium, often outperforming traditional compost in nutrient density [1, 2]. These nutrients are bound within organic compounds, releasing slowly into the soil to feed crops and improve soil structure, water-holding capacity, and long-term fertility [3]. Research from Cornell University shows that vermicompost not only supplies plant-available nutrients but also suppresses soil-borne pathogens, making it a valuable amendment for soil health [4].

For broadacre or horticultural operations, worm castings can play a role in building soil fertility over time-particularly improving organic matter percentages. They’re particularly effective in systems aiming to reduce reliance on synthetic inputs while maintaining productivity [5]. However, as we’ll explore, their application at scale comes with challenges.

Worm Juice Extracts: Delivering Microbial Diversity

Worm cast extracts, like our Worm Brew or the extracts farmers produce on-farm from our Worm Mods, are made by brewing castings in water to extract beneficial microbes and suspend them in liquid. Unlike castings, these extracts don’t carry the same nutrient load because the minerals remain bound to the organic matter in the castings. Instead, their strength lies in delivering diverse microbial populations.

Studies highlight that vermicompost teas contain unique microbial communities, including beneficial bacteria, fungi, and actinomycetes, which differ from those in solid castings [6, 7]. These microbes enhance soil biodiversity, improve nutrient cycling, and make existing nutrients more available to plants [8, 9]. When paired with nutrient applications - such as kelp, fish emulsions, molasses, or synthetic fertilisers like urea, MAP, or DAP - these microbes help convert those inputs into plant-available forms, maximising their delivery.

Complementary Tools, Not Competitors

It’s critical to understand that worm castings and worm cast extracts aren’t in a head-to-head contest. Castings deliver slow-release nutrients and organic matter, while extracts focus on microbial inoculation [10]. Research comparing the two shows that while extracts may carry some soluble nutrients, their microbial profiles are tailored for biological enhancements, not nutrient loading [11]. For broadacre or horticulture, combining extracts with your nutrient program can amplify results, as the microbes unlock nutrients that might otherwise stay unavailable.

Why Not Just Spread Worm Castings?

If worm castings are so nutrient-rich, why not spread them across your paddocks or orchards? The answer comes down to scale and logistics. To match the nutrient levels of common inputs like kelp, fish emulsions, or synthetic fertilisers, you’d need massive quantities of castings - think tonnes per hectare [12]. For large-scale operations, this is neither cost-effective nor practical.

Turning castings into liquid extracts is a far more efficient approach for achieving the desired microbial outcomes easily paired with nutrition applications. Australian farmers already have infrastructure for liquid applications whether through boom sprayers, fertigation systems, or foliar sprays - making extracts a seamless fit for broadacre, pasture, or horticultural setups. This approach saves time, reduces costs, and leverages equipment you’re already using.

Practical Applications for Australian Farmers

For broadacre farmers growing crops like wheat, canola, or barley, Worm Brew or worm juice can be applied alongside liquid fertilisers to enhance nutrient uptake and soil biology. In pastures, they support grass growth by fostering microbial activity that breaks down organic matter, particularly after the heard has left the cell in cell grazing operations. Horticultural producers - whether in vineyards, citrus groves, or vegetable fields - can use extracts in ferigation or as foliar sprays to combat leaf and soil disease.

At Worms Downunder, we’ve seen our clients integrate Worm Brew and on-farm extracts into their operations with great success.

References

  1. Dominguez, J., & Edwards, C. A. (2010). Vermicompost maintains a stable physical soil structure because of the presence of soil macropores and organo-mineral complexes. ScienceDirect Topics. Retrieved from www.sciencedirect.com [Web ID: 16].

  2. Adhikary, S. (2012). Vermicompost, the story of organic gold: A review. Agricultural Sciences, 3(7), 905-917. doi:10.4236/as.2012.37110 [Web ID: 3].

  3. Lim, S. L., Wu, T. Y., Lim, P. N., & Shak, K. P. Y. (2015). The use of vermicompost in organic farming: Overview, effects on soil and economics. Journal of the Science of Food and Agriculture, 95(6), 1143-1156. doi:10.1002/jsfa.6849 [Web ID: 16].

  4. Arancon, N. Q., Edwards, C. A., Atiyeh, R., & Metzger, J. D. (2004). Effects of vermicomposts produced from food waste on the growth and yields of greenhouse peppers. Bioresource Technology, 93(2), 139-144. doi:10.1016/j.biortech.2003.10.015 [Web ID: 9].

  5. Atiyeh, R. M., Edwards, C. A., Subler, S., & Metzger, J. D. (2001). Pig manure vermicompost as a component of a horticultural bedding plant medium: Effects on physicochemical properties and plant growth. Bioresource Technology, 78(1), 11-20. doi:10.1016/S0960-8524(00)00172-3 [Web ID: 9].

  6. Nechitaylo, T. Y., Timmis, K. N., & Golyshin, P. N. (2010). Single-strand conformation polymorphism (SSCP) profiles on the diversity of eight bacterial groups from fresh soil, gut, and casts of earthworms. Environmental Microbiology, 12(6), 1461-1473. doi:10.1111/j.1462-2920.2010.02174.x [Web ID: 5].

  7. Edwards, C. A., & Burrows, I. (1988). The potential of earthworm composts as plant growth media. In Earthworms in Waste and Environmental Management (pp. 211-220). SPB Academic Publishing.

  8. Pathma, J., & Sakthivel, N. (2012). Microbial diversity of vermicompost bacteria that exhibit useful agricultural traits and waste management potential. SpringerPlus, 1(1), 26. doi:10.1186/2193-1801-1-26 [Web ID: 5].

  9. Worm Solutions. (2024). The comprehensive benefits of worm juice. Retrieved from www.wormsolutions.com.au [Web ID: 19].

  10. Scheuerell, S. J., & Mahaffee, W. F. (2004). Compost tea as a container medium drench for suppressing seedling damping-off caused by Pythium ultimum. Phytopathology, 94(11), 1156-1163. doi:10.1094/PHYTO.2004.94.11.1156 [Web ID: 16].

  11. Fritz, J. I., Franke-Whittle, I. H., Haindl, S., Insam, H., & Braun, R. (2012). Microbiological community analysis of vermicompost tea and its influence on plant growth. Environmental Science and Pollution Research, 19(8), 3308-3318. doi:10.1007/s11356-012-0944-8.

  12. Landscape South Australia. (2023). Farm-scale vermicompost systems. Retrieved from www.landscape.sa.gov.au [Web ID: 4].

  13. Urban Worm Company. (2021). Worm castings 101: Your guide to soil’s favorite food. Retrieved from urbanwormcompany.com [Web ID: 18].

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