Vermicompost, compost or bokashi? Choosing your organic input in Zimbabwe

A Harare market gardener, a Murehwa smallholder, and a Bulawayo homesteader could all be standing in the same agricultural supplies shop, each picking up something labelled “organic fertiliser” — and walking out with three completely different products that work in different ways, at different speeds, and suit different situations. That confusion costs money.

This guide separates vermicompost, thermophilic compost, and bokashi clearly: what each actually is, what they do and do not do well, what the current field evidence from Zimbabwe shows, and which to reach for depending on your situation.

Quick note on what we can and cannot claim: where trial results are not yet published, we say so plainly. Where a nutrient value is not independently confirmed, we do not invent one.

Quick comparison: the three types at a glance

Type	What it is	Time to make	Labour / scale	Kills weed seeds & pathogens?	Best for	Watch out for
Thermophilic (hot) compost	Aerobic decomposition of carbon- and nitrogen-rich material at 60–70 °C (FAO)	2–4 months with regular turning	Medium effort; can be field-scale	Yes, if heap reaches 60 °C throughout	Field-scale soil-building; crop residues; manure	Needs regular turning; heat can escape if heap is too small
Vermicompost (worm compost)	Organic matter processed through earthworm digestive tracts (Eisenia fetida) (OSU EM-9034)	3–6 months to first harvest	Low physical effort; small to medium scale	No — cold process; do not add seedy weeds	Seedling trays; transplant holes; high-value beds	Low volume output; cannot process all kitchen waste types; temperature-sensitive
Bokashi	Anaerobic fermentation of organic waste using inoculated bran (effective micro-organisms, a mixed culture developed in Japan) (FAO)	2–4 weeks fermentation + 2–4 weeks soil burial	Very low effort; household scale	No — fermentation does not reach pathogen-killing temperatures; must be buried to finish in soil	Kitchen waste (including meat and dairy); urban/peri-urban households; pre-composting input	Not finished when it comes out of the bucket; must be buried and allowed to mature; acidic smell off-putting

Hot compost: the field-scale workhorse

Thermophilic composting — commonly called hot composting or simply “making a heap” — is the aerobic breakdown of organic matter by bacteria and fungi at temperatures of 60–70 °C (FAO on-farm composting). At those temperatures, most weed seeds and human pathogens are destroyed. The heap needs a minimum volume of about 1 cubic metre to hold heat, a balanced mix of carbon-rich “browns” (stover, dry grass, cardboard) and nitrogen-rich “greens” (manure, kitchen scraps, green weeds), and regular turning every 5–14 days to maintain aerobic conditions.

Finished hot compost — dark, crumbly, smelling of clean earth — improves soil structure, water-holding capacity, pH buffering, and microbial activity (FAO Soils Bulletin 56). It is the most practical way to put meaningful volumes of organic matter onto a field. The limitation is quality variance: a poorly made heap that never reaches temperature is not the same product as one managed well.

Zimbabwe’s SCIT (Scientific Conservation Irrigation Technology) system, developed by PCAT engineer Joseph Ngirande and researched at Harare Institute of Technology, fills planting potholes with a blend of “stick compost” (a form of locally made thermophilic compost) and vermicompost at a 2:1 ratio (The Herald, Sallomy Matare, 13 July 2019, via CFU Zimbabwe). HIT’s EMRECC research centre lists “thermal compost” — alongside vermi-ferts — as a material used in the SCIT technology (EMRECC Research Projects, HIT). Note that EMRECC is a waste-management and renewable-energy research centre; this work sits at the engineering and systems end of agriculture rather than in agronomy research.

For a step-by-step guide to making hot compost from your own farm residues, see making compost from farm waste.

Vermicompost: the precision input

Vermicompost is the product of organic matter passing through the gut of Eisenia fetida — red wigglers or tiger worms. The worm does not simply shred the material; its intestinal tract hosts microbial communities approximately 1,000 times denser than those in the input material (OSU EM-9034). What emerges is a biology-rich, nutrient-dense product that feeds both the crop and the soil food web simultaneously.

Vermicompost is a cold process. The bin never heats up significantly, which means weed seeds and pathogens are not destroyed — do not add seedy weeds or raw meat to a worm bin (OSU EM-9034). Output volumes are modest compared to a field-scale compost heap; most growers use it as a precision tool — in seedling mixes, transplant holes, and high-value beds — rather than a bulk field amendment.

For Zimbabwean conditions, the critical management point is temperature: red wigglers slow sharply above 32 °C and die above 35 °C. In lowveld and mid-altitude summer, bins must be in deep shade. For everything you need to set one up, see vermicomposting and worm farming in Zimbabwe.

HIT’s EMRECC research centre runs an aquaponics/hydroponics/vermiculture project in which kitchen organic waste is converted by worms into “liquid and solid fertilizer” — referred to as “vermi-ferts” — used within a closed-loop food production system (EMRECC Research Projects, HIT). This is a waste-management and food-security research project, not an agronomic field trial, but it illustrates local institutional investment in vermiculture as an organic input technology.

Bokashi: the kitchen-waste fermenter

Bokashi (from Japanese, meaning “fermented organic matter”) is an anaerobic fermentation process using organic matter — including materials that cannot go into a worm bin or compost heap easily, such as meat, fish, and cooked food — inoculated with a mixed culture of effective micro-organisms (EM) on wheat bran or similar carrier (FAO on-farm composting). The sealed bucket ferments rather than decomposes. The process typically takes two to four weeks.

Critical distinction: bokashi out of the bucket is not finished compost. It is pre-fermented material that must be buried in soil and allowed to mature for a further two to four weeks before it is safe to plant into. If applied directly to growing plants, its low pH (around 3.5–4.5 during fermentation) can damage roots.

Bokashi excels at one specific job: handling kitchen waste that other methods cannot — including cooked food, meat scraps, and dairy. It is almost no-effort (fill the bucket, add bran, press down, seal), fits in a flat, urban kitchen, and processes waste quickly. What it does not do is replace the soil-building role of bulk compost — the volumes are too small and it must be buried to finish.

The bokashi liquid drain-off (“bokashi juice”) is typically diluted heavily — often 1:100 to 1:200 — and applied as a soil conditioner or drain cleaner. Evidence for its agronomic value as a nutrient input is limited; do not rely on it as a fertiliser.

What the CIMMYT RAIZ trials show — and what they do not yet show

The Resilience Building through Agroecological Intensification in Zimbabwe (RAIZ) project — led by CIMMYT in partnership with CIRAD and the University of Zimbabwe, funded by the European Union — is running on-farm trials in Murehwa (Natural Region II) and Mutoko (Natural Region IV), Mashonaland East province. These districts have been chosen specifically because their sandy, low-organic-carbon soils typify the challenge facing Zimbabwe’s smallholder farmers.

The RAIZ trials are testing five organic amendments: vermicompost (from ZimEarthworms), bokashi, Orgfert, Atlas orgfert (organic D), and cattle manure, under both conventional and conservation agriculture (CA) management, including intercropping systems (CIMMYT blog, June 2025). The 2023/24 season involved 51 farmers in farmer-led experiments.

What the 2023/24 season actually found: erratic rainfall ranging from 250 to 500 mm meant maize harvests were limited across all treatments. Bokashi showed improved performance compared to the previous season. Atlas orgfert (organic D) was preferred by farmers based on visual crop vigour and yield observations. Vermicompost performed particularly well when combined with Compound D fertiliser, suggesting a synergistic effect between organic and synthetic inputs. Site-specific conditions — slope, soil type, mulch availability — heavily influenced outcomes. Termite infestation was a variable at some Mutoko sites (CIMMYT blog, June 2025).

Published results from peer-reviewed analysis of the RAIZ trials are not yet available. What has been published is a CIMMYT blog (June 2025) summarising early field observations and farmer responses from the 2023/24 season. The trials are ongoing. That said, the question RAIZ is asking — how do these organic inputs compare on Zimbabwe’s actual soils under actual conditions, and which are affordable and accessible to smallholders? — is exactly the right question, and the answer matters enormously to this readership. We will update this page as results emerge.

How they differ in practice: the key dimensions

Nutrient availability

All three improve plant nutrition, but by different mechanisms and at different speeds. Hot compost releases nutrients as it mineralises across the growing season — a slow, sustained release (FAO Soils Bulletin 56). Vermicompost contains nutrients in more immediately plant-available forms, delivered with a concentrated microbial inoculum (OSU EM-9034). Bokashi, once buried and matured in soil, releases nutrients as the fermented material is broken down by soil biology — timing and availability depend on soil temperature and moisture.

None of these is a like-for-like replacement for mineral fertiliser; they work over different timescales and build different aspects of soil health. See organic vs inorganic fertiliser — what Zimbabwe’s trials show for that comparison.

Moisture-holding

Compost, vermicompost, and bokashi-amended soil all improve moisture retention by increasing organic matter. The mechanism is the same for all three: organic matter — particularly humus — holds water in pore spaces. FAO puts it plainly: 1 kg of humus can hold up to 6 litres of water (FAO). On Zimbabwe’s sandy granitic soils, this is arguably more important than the direct nutrient content.

Weed seeds and pathogens

Type	Weed-seed kill	Pathogen reduction
Hot compost (well managed, 60 °C+)	Yes	Yes (FAO on-farm composting)
Vermicompost	No	Partial (worm gut has some effect but not reliable)
Bokashi	No	No — fermentation does not reach pathogen-killing temperatures

This matters if you are adding material from areas with heavy weed pressure or if you are using inputs on vegetables that will be eaten raw.

Scale

Hot compost can be produced at field scale — windrows, large heaps — and is the only one of the three realistically suited to treating a full hectare. Vermicompost is homestead- to small-market-garden scale. Bokashi is household scale, primarily urban or peri-urban.

Suitable inputs

Input type	Hot compost	Vermicompost	Bokashi
Crop residues (stover, straw)	Excellent	Not ideal — too fibrous for worm bins	Not suited
Cattle / goat manure	Excellent	Small amounts (aged)	Not suited
Kitchen fruit/vegetable scraps	Good	Excellent	Excellent
Meat, fish, cooked food	Do not add	Do not add	Yes — this is bokashi’s unique advantage
Weeds (no seeds)	Good	Acceptable	Possible
Weeds with seeds	Kills seeds if heap reaches 60 °C	Do not add	Do not add

Which should you actually use? Decision by situation

You have kitchen waste at home and no outdoor space

Bokashi is your answer. It handles the full range of food waste including cooked food, is odourless when sealed, and fits on a kitchen shelf. Bury the output in a corner of a bed or pot every month. If you do have outdoor space, a small worm bin handles fruit and vegetable scraps better and produces a more immediately useful product.

You have farm residues (stover, straw, manure) to deal with

Hot compost. Worm bins cannot handle stover-scale volumes. Bokashi is not designed for fibrous crop waste. A properly made heap at 1 cubic metre minimum, turned regularly, will give you dark, crumbly compost in two to four months that you can apply across a full plot. See making compost from farm waste.

You are running a market garden and need quality for seedlings

Vermicompost for seedling trays and transplant holes; hot compost for general bed preparation. The combination mirrors what SCIT work has shown: concentrated vermicompost where it matters most (root zone at planting), bulk compost for the wider soil. See compost in the planting station for planting-hole practice.

You are growing a field crop (maize, sorghum, groundnuts)

Hot compost is the only realistic option for field-scale coverage. Vermicompost output is too small and bokashi is domestic scale. If you cannot make enough at home, see the note on ready-made compost below.

You are an urban or peri-urban grower with limited space and time

Bokashi handles waste with minimum effort. A small worm bin on a shaded verandah gives you vermicompost for whatever beds or pots you have. Neither requires a compost heap.

You have no time to make any of it

Be honest with yourself: a compost heap requires management (turning, moisture checks), a worm bin requires feeding and monitoring, and bokashi requires regular emptying and burial. All three produce better results with consistent attention. If your situation does not allow for that — seasonal labour pressure, a large plot, or limited water for heap management — a ready-made sieved compost may be the practical answer.

An honest note on PCAT BLOCK C

PCAT BLOCK C Organic Compost is a thermophilic (hot) compost — not vermicompost and not bokashi. It is PCAT’s own sieved, field-proven compost, sold in 50 L bags at US$20.

A few things worth being direct about:

It is not the same as SCIT’s stick compost + vermicompost 2:1 mix. SCIT uses a specific combination of locally made compost and vermicompost in a precision planting-hole system. PCAT BLOCK C is a single, standardised product designed for volume and consistency across different farm situations.
Its independent NPK analysis is still with the laboratory. We will publish confirmed values when the results are back. We are not inventing numbers in the meantime.
A well-made home compost from your own materials is not inferior to a commercial product if you have the inputs, time, and management to make it properly. PCAT BLOCK C is useful because it is standardised and sieved — you know what you are getting — and because most farms cannot produce the volume a full land needs from their own inputs alone.

Many growers do both: a small worm bin for seedling mixes and transplant holes, home-made compost where they can, and PCAT BLOCK C to top up the volume and quality a full plot requires. That is a reasonable programme.

Frequently asked questions

Is vermicompost better than ordinary compost? Different, not simply better. Vermicompost is richer in immediately available nutrients and microbial life per kilogram, but you can only produce it in modest volumes and it does not kill weed seeds (OSU EM-9034). Hot compost can be made at field scale and kills weed seeds and pathogens at 60 °C (FAO on-farm composting). They serve different roles. The ideal system often uses both.

Is bokashi safe to use on vegetables? The fermented material out of the bucket is not — it is too acidic and too raw to apply directly to plants. Bury it at least 20 cm deep and wait two to four weeks before planting in that spot. Once fully matured in soil, it is safe. The RAIZ trials in Murehwa and Mutoko are among the first systematic assessments of bokashi’s agronomic performance on Zimbabwe’s sandy soils; results from full published analysis are not yet available (CIMMYT, June 2025).

Can I mix vermicompost and compost when I fill planting stations? Yes. The SCIT system developed at HIT uses stick compost and vermicompost at a 2:1 ratio in planting potholes precisely because the two products complement each other — bulk organic matter from the compost, concentrated biology and available nutrients from the vermicompost (The Herald, Sallomy Matare, via CFU Zimbabwe). See compost in the planting station for practical guidance.

Why did the CIMMYT RAIZ trials not give a clear winner between bokashi, vermicompost, and compost? Because there is no universal winner. Erratic rainfall (250–500 mm) in 2023/24 constrained yields across all treatments. Site-specific factors — slope, termite pressure, mulch availability — heavily influenced results. Farmer-preferred inputs (Atlas orgfert) differed from those showing synergistic effects with mineral fertiliser (vermicompost + Compound D). That complexity is the honest finding: the right organic input depends on your soil, your waste stream, and your management capacity (CIMMYT blog, June 2025).

How much of any of these do I apply? It depends on your crop and your soil’s baseline organic matter. Do not apply any of these at a rate you have read in a generic article without understanding your soil first. See how much compost per crop in Zimbabwe for documented rates by crop, and read your soil before you spend for the starting point.

Can I make liquid feed from any of these? Yes. Vermicompost steeped in water makes a useful microbial and nutrient liquid. Bokashi juice (the drain-off from the bucket) is sometimes applied diluted, though its agronomic value as a plant feed is not well established. Hot compost steeped in water makes compost tea. For the evidence on what these liquids actually do — and the safety rules for applying them — read compost tea and liquid feed.

Do this now

Work out what waste you actually have — kitchen scraps only, or farm residues and manure too? That single question narrows your choice significantly.
If you have farm residues and manure, start a compost heap: see making compost from farm waste.
If you want better seedlings, set up a small worm bin: see vermicomposting in Zimbabwe.
If you are urban with kitchen waste only, try bokashi — bury the output monthly in your beds.
Test your soil before you decide on rates — see read your soil before you spend.
Do not use manure-based liquid feeds on edible leaf crops within two weeks of harvest — see the safety section in compost tea and liquid feed.
Watch the RAIZ trial results — CIMMYT’s ongoing work in Murehwa and Mutoko will give Zimbabwe-specific evidence on which organic inputs perform best on granitic sandy soils. We will publish a summary when peer-reviewed results are available.

PCAT BLOCK C Organic Compost — a ready-made, sieved thermophilic compost for growers who need volume and consistency. Not a substitute for knowing your soil. US$20 per 50 L bag.