When it comes to soil health and nutrition in kiwifruit orchards, organic amendments like compost and worm castings (vermicast) are popular options. Both improve soil quality, but they work in different ways. So, what’s the difference between them, and which one is the best choice for your orchard?
Compost is made by breaking down organic waste such as green waste, wood waste, manure, and food scraps through microbial and fungal decomposition at high (65oC+) temperatures. The result is a stable, humus-rich material that improves soil structure, aeration, and water retention. However, its nutrient content and microbial life can vary depending on the feedstock and composting process.
✔ Adds bulk organic matter – Helps improve soil structure and moisture retention.
✔ Contributes to long-term soil health – Over time, organic matter builds soil resilience.
✔ Can be locally sourced – Availability and price vary depending on supplier.
✖ Higher upfront cost per tonne – Generally more expensive than vermicast per tonne.
✖ Highly variable nutrient content – Nutrients aren’t always in plant-available forms and nutrient content varies depending on the quality of the feedstock the compost is derived from.
✖ Higher C:N ratio - Compost will often come with some remnant woody or undegraded material which, when applied, may continue to degrade in your soil. If the C:N ratio is high this can immobilise nitrogen which prevents your crops from being fed.
✖ Inconsistent microbial life – Due to the higher temperature of the initial composting, larger fungal populations and smaller microbial populations will be present. While some lower temperature microbial populations will colonise during the compost maturation these wil typically be in much smaller numbers.
Worm castings, or vermicast, are created when composting worms digest organic matter, producing a fine, crumbly material, rich in nutrients, beneficial microbes, and humic substances. Vermicast delivers highly bioavailable nutrients and actively enhances soil biology.
✔ Lower cost per tonne – Generally more affordable than compost per tonne.
✔ Large microbial community – As a result of processing through the worm’s gut, worm castings are packed with beneficial plant growth promotors, bacteria and fungi that support plant health and help to suppress plant disease.
✔ Bioavailable nutrients – Provides a plant-available, stable nutrient supply.
✔ Improves soil structure and water retention – Helps maintain moisture and supports root development.
✔ Lower C:N ratio and more stablised – Unlike compost, vermicast is created as a result of processing through the worms gut. The resulting output of worm castings is more consistent in nature, rather than containing unprocessed or remnant woody materials .
✖ Availability (and therefore transport) close to the orchard site can be a challenge – MyNoke’s vermicast is available from our Tokoroa, Taupō and Ohakune sites, in the central North Island.
When it comes to soil health in kiwifruit orchards, both compost and worm castings (vermicast) offer valuable benefits. Both compost and vermicast are used to add bulk organic matter, to improve soil structure and moisture retention. Depending on the compost, there can be a high degree of nutrient content and microbial life variability. Vermicast on the other hand is a concentrated soil booster, rich in microbes and bioavailable nutrients at a more consistent level, that enhance long-term soil fertility. Check out our comparison table to work out what may be best for your kiwifruit orchard’s needs.
Both amendments are typically applied at 10–20 tonnes per hectare, with the volume depending on your orchard’s specific needs. Both compost and vermicast add organic matter and structure to soils, with vermicast typically carrying a lower cost per tonne, being easier to spread and incorporate into the soil, as well as the added benefit of microbial diversity, plant growth regulators and nutrients being more bioavailable.
Many orchard managers find the best results by switching from bulk compost applications to targeted vermicast use. Applying vermicast at key times in the season can improve soil fertility and reduce reliance on synthetic inputs, leading to healthier vines and better fruit quality.
Is vermicast right for your kiwifruit orchard?
At MyNoke, we produce high-quality vermicast designed to support thriving kiwifruit orchards. Contact us via our online form or give us a call on 0800 MYNOKE to learn how worm castings can help you grow stronger, more resilient vines.