Bokashi - Japan - ARI - Introduction to Bokashi
by the Asian Rural Institute
submitted January 2020
Introduction to Bokashi
What is bokashi?
Bokashi is a fermented fertilizer made by mixing organic materials, soil, and bio-char (like rice husk charcoal or wood charcoal) with indigenous microorganisms (IMOs). Bokashi means thinning (gradation) in Japanese. Unlike traditional compost and fertilizer, soil is added to the organic materials, and the mixture is fermented. Soil thins down the consistency of this fertilizer. Therefore we call this fertilizer Bokashi.
To learn how we make Bokashi at ARI, click here:
Why do we use bokashi?
If raw materials like rice bran or oil cake are applied to the field directly, as they decompose, they use oxygen and generate harmful gasses like methane and ammonia. This has a bad influence on the growth of plants. Applying fresh manure directly to a field can also have negative consequences, including the high nitrogen content of the manure burning the root zone of the plants. Furthermore, applying raw organic matter directly to the field can attract harmful insects.
Bokashi solves these problems by fermenting the organic matter and manure. This makes the nutrients more accessible to the plant. Because of fermentation, bokashi does not have a strong smell, and it can be stored for up to one year without degrading. Bokashi is also a good choice because the recipe is versatile. As long as IMOs are used, nearly any organic matter can be decomposed and turned into good fertilizer.
Here is a comparison of bokashi to chemical fertilizers and compost
Why does bokashi use fermentation?
Fermentation is a type of chemical reaction caused by microorganisms or enzymes that split complex organic compounds into relatively simple substances. In the process of making bokashi, microorganisms not only decompose organic compounds into absorbable nutrients for the plant, but also produce plant hormones, vitamins and high energy phosphoric acid compounds such as ATP, ADP, and GDP.
Benefits of fermentation:
to avoid harmful gasses such as methane gas and ammonia gas and prevent lack of oxygen
to prevent harmful insects (raw organic materials attract a lot of insects)
to decompose organic materials into absorbable nutrients for plants
to kill germs by heat, which occurs in the process of fermentation
to provide biological diversity of microorganisms
to produce plant hormones, vitamins, and so on
Almost any organic material can become bokashi. We use resources that are local to Japan to make our bokashi at ARI. The recipe we use for bokashi is 7 parts chicken manure (from poultry house fermented flooring), 4 parts soil, 2 parts rice husk charcoal, 1 part rice bran, 4-5 handfuls of IMO3 and water.
7 parts (or containers as above)
Any type of manure can be used, but chicken manure works best because chickens have a short digestive tract so their manure is less digested and has a higher macro-nutrient concentration. The manure should be collected when it is fresh and allowed to dry in a shaded place for about 1 month before use. At ARI, we use the fermented bedding from the chicken house floor. This includes chicken manure which has been "diluted" with rice husk, wood chips, or saw dust. If you are using pure chicken manure (that is not diluted) you will need to use less than 7 parts.
Here is the macronutrient composition of common manure sources:
Chicken manure (N 3-5%, P 5-9%, K 3-4%)
Pig manure (N 3-4%, P 5-6%, K 0.6-2%)
Cow manure (N 2-2.5%, P 1-5%, K 1-2.5%)
contains nutrients (Nitrogen, Phosphorous, and Potassium)
contains trace minerals
is broken down by IMOs so that the nutrients are more easily absorbed by plants
1 part (container) flour or powder or bran
Any flour, powder, or bran can be used as a source of carbohydrates including from wheat, corn, soybean, sweet potato, or cassava. At ARI, we use rice bran because it is widely available and relatively inexpensive.
are a food source for IMOs
have high water holding capacity
have high nutrient holding capacity
2 parts (containers) biochar
Biochar is a carbon-rich charcoal created by carbonizing crop residues (like corn stalks or rice husks), manure, or wood at low temperatures. At ARI, we make and use rice husk charcoal because rice husks are easily available. Biochar can also be omitted from bokashi.
To learn how we make rice husk charcoal at ARI, visit this page:
provides a place for IMOs to grow in the pores within the charcoal
helps neutralize the pH of the soil
has a high water holding capacity and provides soil aeration
contains phosphorous, potassium, and calcium
4-5 handfuls of IMO3
Indigenous microorganisms are the catalyst for fermentation in bokashi. While you can buy effective microorganisms from the store, collecting your own indigenous microorganisms works even better and is free! You can grow your own IMOs using the following process.
IMO1 - Collect indigenous microorganisms from the local environment. The collection process includes building a trap out of a bamboo container, filling it with rice and burying it in the woods 20cm deep. After 10 days, dig up the container. The rice should be covered in a white mold, which is IMO.
IMO2 - IMO1 is mixed with an equal amount of brown sugar, covered, and left to ferment for 2 to 3 weeks.
IMO3 - IMO2 is mixed with one part soil and one part rice bran.
To learn more about how to collect IMOs, visit the IMO page:
In place of IMO3, bokashi that has been made within the last year can be used, since it already contains IMOs.
speed up the decomposition process
decompose organic compounds into absorbable nutrients
produce plant hormones, vitamins and high energy phosphoric acid compounds such as ATP, ADP, and GDP
4 parts (containers) clay soil or subsoil
Bokashi is different from most other fertilizers because it is thinned out with soil. If you try to make bokashi without soil, a lot of nitrogen is lost in the process of fermentation. When you make compost, you can smell ammonia gas. That means a lot of nitrogen is being lost into the air.
Soil also helps to hold the organic matter (and especially nitrogen) in the root zone of plants. It has a high nutrient-holding capacity and makes the fertilizer more stable, so the nutrients last longer. Soil thins down the density of nutrients, too. It reduces the chance of root burning, which can happen when nutrients are applied too densely. Furthermore, soil provides a place where microorganisms can live. These micro-organisms have an important role in bokashi fertilizer.
absorbs and preserves nutrients
absorbs bad smells
sustains the nutritious effect of bokashi
reduces the concentration of nutrients, which reduces the potential for root burning
gives a living space for micro-organisms
When making bokashi, the moisture content should be around 50%. You can check this by squeezing a handful of the mixture. You want the mixture to form a ball in your hand that crumbles apart easily. If water squeezes out, your mixture is too wet. If the mixture crumbles in your hand and does not form a ball, add more water.
Bokashi needs air to ferment. It is important to cover the bokashi with a breathable material like straw or a blanket during fermentation. If a plastic tarp is used, the temperature will get too high and the microorganisms will be killed.
As you consider the local resources available in your area to make bokashi, here are some common ingredients that can be included in order to increase specific macronutrients.
Nitrogen (N): fish meal, oil cake, chicken manure, Fish Amino Acid (FAA)
Phosphorus (P): bone powder, rice bran, chicken manure, Water-soluble Calcium Phosphate (WCaP)
Potassium (K): ash (effect of decreasing germs), chicken manure, stems of tobacco
How to use bokashi
It is most effective to apply bokashi near the plant roots. When transplanting fruits and vegetables into a field, the bokashi can be added to the hole into which the plant will be placed. The soil in bokashi holds nutrients (especially phosphorus) very tightly, so the nutrients are only available to the plant if it is applied near the roots. Because bokashi is thinned out with soil, it does not burn the roots of plants. Applying bokashi around the roots provides the appropriate environment for interaction between microorganisms, plants, and soil.
Here are some common ratios we use for applying bokashi to different fruit and vegetable crops. When applying bokashi to a crop that has already been planted, it is best to apply the bokashi between the rows so that it can be absorbed slowly. Usually we apply at a rate of 200kg per 0.1 hectare.