How to apply BSF frass fertilizer without relying on a one-size-fits-all dosage.

Why there is no single correct BSF frass dosage

Published research shows that black soldier fly frass can perform well as an organic fertilizer in some crops and conditions, but it also shows why application rates cannot be transferred blindly from one study, product or farm to another.

Frass composition can vary with larval feedstock, rearing conditions and post-processing. Soil fertility, crop demand, climate and the rest of the nutrient programme also influence the rate that makes agronomic sense. A field rate used in a maize experiment in one country is therefore evidence about that experiment—not an automatic recommendation for oil palm, durian, vegetables or another Malaysian crop.

A better way to determine application rate

Rather than begin with a universal rate, use a five-step decision process.

Common application methods

The physical placement method depends on the crop, field layout, equipment and the finished product instructions. Three general approaches commonly discussed for organic soil inputs are broadcasting/incorporation, localized placement and placement around established tree root zones.

Broadcasting and incorporation

Broadcasting spreads material across a larger soil area. Where incorporation is appropriate, mixing the fertilizer into the upper soil profile can reduce the risk of material remaining exposed on the surface and place nutrients closer to the active soil zone. The appropriate incorporation depth depends on crop and cultivation system, so a fixed depth should not be presented as universal.

Localized or band placement

Localized placement concentrates the material closer to the crop row or active root zone. This may improve placement efficiency in some systems, but excessive concentration can also create nutrient, salinity or ammonia-related problems depending on the product. The finished product recommendation should therefore guide how close and how concentrated the placement should be.

Established trees and plantation crops

For tree crops, fertilizer is generally placed where active feeder roots can access it rather than piled directly against the trunk. Canopy size, root distribution, slope, ground cover, irrigation and rainfall all affect the best placement pattern. A single “holes versus trench versus circle” instruction should not replace crop-specific agronomic judgement.

Timing around Malaysian rainfall

Malaysia's high rainfall means fertilizer timing should consider runoff, erosion, waterlogging and nutrient movement. A practical principle is to avoid applying fertilizer immediately before forecast heavy rain or onto already waterlogged ground where material can be washed away or nutrient losses are more likely.

Moderate soil moisture can support nutrient movement and biological activity, but “pre-monsoon” and “post-monsoon” dates should not be treated as fixed national schedules. Rainfall patterns differ by location and season, and irrigation-managed farms have different conditions from rain-fed plantations.

Should frass and mineral fertilizer be used together?

They can be part of the same nutrient-management programme, but there is no evidence-safe rule that every grower should automatically reduce mineral fertilizer by 25%, 30% or another fixed percentage when adding frass.

Published studies demonstrate that frass can supply nutrients and, in some experimental systems, substitute for part of a mineral or alternative fertilizer programme. The correct substitution level depends on nutrient analysis and crop requirement. A fixed percentage reduction without nutrient accounting can create either deficiency or over-application.

Why published research rates should not be copied directly

For example, a 2020 field study in maize tested several tonnes-per-hectare and nitrogen-equivalent frass rates and reported positive yield and nitrogen-use-efficiency results under those experimental conditions. That study is valuable evidence that frass can work as a fertilizer, but the authors themselves framed the work around a specific maize system and specific fertilizer material.

Later reviews also highlight substantial variability among frass products and note that excessive concentrations can impair plant growth in some cases. This is exactly why a study rate should be converted into a commercial recommendation only after product, crop and local-condition validation.

Crop-specific questions to answer before applying

Oil palm

What is the palm age, current nutrient programme, soil condition, leaf/soil analysis where available, rainfall pattern and intended role of the organic fertilizer?

Durian and other fruit trees

What is the tree age, canopy/root-zone condition, phenological stage, soil pH and existing fertilizer schedule? Nutrient management around flowering and fruiting should not be reduced to one generic rate.

Vegetables

What is the crop cycle, bed preparation method, soil or media fertility and salt sensitivity? Short-cycle crops can respond quickly to both nutrient adequacy and excessive concentration.

Nursery and young plants

Young plants may be more sensitive to excessive salts, ammonia or concentrated nutrient placement. Product maturity and rate should therefore be particularly well controlled.

Storage and handling

Storage recommendations should follow the final Terbit product label and packaging specification once approved. As a general principle for dry organic fertilizer products, protect the material from rain, uncontrolled moisture, contamination and damaged packaging. Do not publish claims about microbial shelf life, pest resistance or odour stability unless the finished product and storage testing support them.

What not to claim before validation

• a universal kilograms-per-acre or kilograms-per-tree rate for all Terbit customers;
• a guaranteed percentage reduction in chemical fertilizer;
• a guaranteed time such as “visible results within 3–4 weeks”;
• that over-application cannot burn or damage plants;
• that the product is automatically safe around aquaculture or livestock systems;
• that it will reliably correct soil pH, suppress pathogens or increase yield by a fixed amount.

Frequently asked questions

Can Terbit publish a dosage table before sample distribution?

Only if the underlying finished product specification and crop guidance are sufficiently validated. Until then, the website should explain the decision process rather than create false precision.

Can I replace chemical fertilizer completely?

That decision should depend on crop nutrient demand, the nutrient contribution of the frass and the rest of the fertility programme. Complete replacement should not be assumed.

Is more frass always better?

No. Research includes examples where excessive frass concentrations reduced plant performance, reinforcing the need to control rate and product quality.

Should I apply before rain?

Avoid imminent heavy rainfall or waterlogged conditions that can increase runoff and nutrient loss. Local weather, soil drainage and the product instruction should guide timing.

Can I use old Terbit dosage figures from the legacy website?

They should not be treated as current V2 recommendations unless Terbit republishes them after validation. The V2 website intentionally distinguishes legacy content from approved product guidance.

Terbit's current application-guidance plan

Terbit currently plans Organic Fertilizer sample distribution from October 2026. That sample period is an opportunity to combine product analysis, controlled usage guidance and structured customer feedback. November–December 2026 can then be used to refine product information before the planned January 2027 online-sales stage.

Future crop-specific dosage tables should be version-controlled and tied to the finished commercial product. Where appropriate, Terbit should state the crop, product analysis, application basis and limits of the recommendation rather than presenting isolated numbers without context.

References and further reading

1. Frontiers in Plant Science (2020): field evaluation of BSF frass fertilizer rates in maize.
2. Environment, Development and Sustainability (2024): systematic review of BSF-derived feed and fertilizer products.
3. Journal of Environmental Management (2024): review of BSF frass composition, plant growth and sustainability research.
4. Frontiers of Agricultural Science and Engineering (2026): review of field application, crop yield and soil-health research on BSFL frass.