Top dressing is how you feed a living soil system without disrupting the biology underneath. This is my amendment blend — built around slow-release nitrogen sources, calcium, trace minerals, and biological activators. Two application strategies depending on how hands-on you want to be.
What Is A Living Amendment Mix?
In a living soil system the goal is feeding the soil biology, not the plant directly. A top dress amendment mix sits on the soil surface and breaks down slowly as water and microorganisms process the ingredients. The biology converts those raw inputs into plant-available nutrition over weeks.
This approach is fundamentally different from liquid feeding. You're not delivering nutrition in a form the plant can immediately uptake — you're building the soil's capacity to feed the plant continuously. The soil becomes the feeding system.
The Recipe
Slow-release nitrogen + natural IPM compounds. Feeds biology and suppresses soil pests.
Chitin, calcium, nitrogen. Feeds chitin-digesting bacteria that suppress fungus gnats and root pathogens.
Phosphorus and calcium. Supports root development and flower formation.
Triacontanol — a natural growth stimulant. Nitrogen source and microbial food.
Growth hormones, trace minerals, microbial stimulant. Supports vigorous biological activity.
Calcium and sulfur. Improves soil structure and drainage without affecting pH.
Volcanic trace minerals — silicon, iron, micronutrients. Slow release through the entire cycle.
Broad spectrum trace minerals from ancient sea bed deposits. Fills mineral gaps.
Magnesium sulfate. Keep low — Mg competes with Ca. 0.5 cup per batch is the ceiling.
Biochar — creates habitat for beneficial microorganisms and improves water retention.
Adds aeration and drainage at the surface. Breaks down slowly adding silica over time.
Fermented organic matter loaded with beneficial microorganisms. Accelerates breakdown of other amendments.
Earthworm Castings: 8 cups — biological activator, plant-available nutrition, microbial inoculant.
Total volume: 46.5 cups = 744 tablespoons per batch.
Option 1 — Slow & Steady
1 tablespoon per gallon of container size, every 7–10 days. Water in after application with plain water, compost tea, or FPJ.
Best for veg and early flower in small to medium containers (2–7 gallon). Gentle feeding with low burn risk. Easy to adjust based on plant response. Keeps microbial life consistently active between applications.
Example: 5 gallon pot = 5 tablespoons every 7–10 days.
Option 2 — Heavy Charge
12 tablespoons (¾ cup) per 5-gallon pot every 2–3 months. Water thoroughly after application. Slow breakdown over 8–12 weeks.
Best for transplanting, building soil before a long veg cycle, or less frequent maintenance. More forgiving for busy schedules. One application covers months of slow-release nutrition.
Combining Both Strategies
The most effective approach layers both methods:
Transplant day — apply 12 tablespoons as a base top dress. Then starting week 3, apply 1 tablespoon per gallon weekly if you see signs of hunger, stretch, yellowing, or heavy growth. Stop top dressing 10–14 days before harvest to allow the soil to flush naturally.
Bag Sizing
744 total tablespoons per batch. At 12 tablespoons per bag that's 62 bags — each one a single transplant charge for a 5-gallon pot, or a 12-week weekly feeding cycle at 1 tablespoon per week.
Neem cake is the ingredient I was hardest to source locally at first. Most hydro shops don't carry it but it's available online and worth ordering in bulk. The IPM benefits alone justify it — neem cake in the soil significantly reduces fungus gnat pressure without any other intervention.
The horticultural charcoal volume looks high at 8 cups but it's intentional. Hawaii's rain and humidity mean you want every advantage in drainage and water regulation you can get. Biochar creates permanent habitat for beneficial microorganisms and helps buffer water in both directions — holding moisture during dry periods and improving drainage during wet season.
Dry bokashi is something I started making myself — fermented kitchen scraps using a bokashi bran inoculant. Adds a completely different biological profile to the mix than the other inputs. If you're not making bokashi yet it's worth starting — the inputs cost almost nothing and the biology it adds to a top dress is exceptional.
Stay Connected
New articles, garden updates, experiments, events, meetups, and community projects.
