Burying bokashi in the garden: depth, how long to wait before planting and mistakes to avoid

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Your bucket has fermented for two weeks, it smells sour and a white film covers the surface: well done, the first stage has worked. But what you have in your hands is not compost yet. It is a pre-compost, acidic and stabilised, which now needs to meet the life in the soil to become earth.

Burying it in the garden is the simplest and most effective way to make use of it. You still need to do it in the right place, at the right depth, and give the soil time to do its work. Here is the method, the timings and the mistakes to avoid.

Why bury it: from acidic pre-compost to soil

In the bucket, lactic acid bacteria have acidified the waste without really breaking it down: the peelings are softened but still recognisable. Once in the ground, everything changes. Oxygen returns, and bacteria, fungi and earthworms take over. The pH rises, the material breaks up, and within a few weeks the meal leftovers become soil.

This transformation has a practical consequence: for the first few days, the burial area is an acidic and very nutrient-rich environment. In a trial on spinach, soil into which a large dose of bokashi had just been incorporated contained around 288 mg of ammonium per kilo, compared with about 5 in the control soil. This level had fallen back to around 14 mg/kg six weeks later. Nothing to worry about for the soil, but it is a good reason not to put young roots in contact with fresh bokashi.

Did you know?

Earthworms shun bokashi for the first few days because of its acidity. After that, they happily colonise it: this is often when you find lots of worms in the burial area.

Trench or holes: how deep?

You don't need a vegetable patch: a corner of the garden, the foot of a hedge or the space between shrubs all work very well. Recommendations range from 10 to 30 cm depending on the source. We advise digging a trench or holes 20 to 30 cm deep. That is deep enough that animals (dogs, foxes, birds) won't be tempted to scratch at it, and shallow enough to stay in the most active layer of soil.

We prefer a trench: the bokashi spreads out in a thinner layer, touches more soil and transforms faster. A 15-litre bucket fits comfortably in a trench about a spade's width wide and a metre long. If you only have small free spaces, several holes are better than one big one.

If local animals are very persistent, dig deeper and cover the area with fine mesh while it transforms. We go into these situations in detail in the guide Problems after burying. On the diagram: the bokashi mixed with soil at the bottom of the trench, at 20 or 30 cm (1), and established plants, kept about 30 cm away (2).

Mix it with soil rather than dropping in a block

This is the step that makes the biggest difference. A compact block of bokashi dropped at the bottom of a hole stays acidic and wet for longer, and can smell bad. Mixed with soil, it transforms much more quickly.

1. Dig the trench and set the soil aside.
2. Empty the bucket into the bottom and spread the contents over a few centimetres.
3. Chop it up roughly with the spade, mixing it with about 2 to 3 times its volume of soil.
4. Fill in with the rest of the soil, so that nothing is visible any more.
5. Water lightly if the soil is dry, then cover with dead leaves or mulch.

Emy's tip

Push a small stake into the ground wherever you bury a bucket, with the date written on it. You'll know when you can plant there, and you won't dig the next bucket into the same spot.

Away from roots: the right distance

Fresh bokashi is acidic and rich in salts and ammonium. In direct contact with roots, it can damage them. Keep a distance of about 30 cm from established plants. The roots will find their way to the nutrients by themselves once the area has turned into soil.

How long to wait before planting

Reliable sources agree on one point: you don't sow or plant straight away. Our guidelines:

• at least 2 weeks in warm, living soil, in late spring or summer;
• 3 to 4 weeks is even better, and it is the waiting time we recommend by default;
• longer in cold, heavy or compacted soil: allow up to 6 to 8 weeks in early spring or late autumn.

How do you know when it's ready? Scrape away a little: the soil should no longer smell sour, and the waste should be almost unrecognisable. A few hard pieces (fruit stones, bones, thick stalks) may still be lying around: they will disappear over the following weeks and won't get in the way of planting. If the sour smell persists beyond two weeks, it is often because the bokashi was too concentrated or not mixed enough.

Key points

20 to 30 cm deep, 2 to 3 volumes of soil for 1 volume of bokashi, 30 cm from roots, and at least 2 weeks before planting (3 to 4 is better, longer in cold soil).

Rotating beds in the vegetable garden

In the vegetable garden, the ideal is to bury bokashi in an empty bed a few weeks before growing in it. Work on a rotation: each bucket goes into the next bed, and you plant where you buried a month earlier. In practice:

• in spring, bury in the beds that will take hungry vegetables (squash, tomatoes, cabbages) in May or June;
• in summer, use the beds freed up after harvests (potatoes, peas);
• in autumn, bury in the beds that will stay bare all winter.

If the ground is frozen, don't force it: a fermented bucket keeps sealed for several months, even in the cold. You'll find our advice in the guide Bokashi in winter, in summer and during the holidays.

Trees, hedges, flower beds: how to go about it

For trees and shrubs, dig holes 25 to 30 cm deep beyond the edge of the canopy, where the fine roots that absorb water and nutrients are found. Mix the bokashi with the soil you've dug out, fill in and water lightly. Change position each time, working your way round the tree.

In an established flower bed or hedge, dig small trenches between the rows or between the clumps, keeping the right distance from the roots. For perennials, a few small, well-spread additions are better than a whole bucket in one spot.

What you should never do

• Spread bokashi on the surface or use it as mulch. Exposed to the air, it dries badly, smells and attracts flies and animals. Kitchen bokashi is always buried. Not to be confused with EM Bokashi mulch for soil, a different, dry product designed to be spread.
• Put everything in a single hole, season after season. The area becomes too concentrated and takes a long time to transform.
• Plant the same day in the burial area.
• Bury it at the foot of a plant hoping to feed it directly.
• Forget to rinse the bucket with clean water before filling it again.

No garden, or no room to dig? There are other solutions, from a large tub of soil on the balcony to a composter: see our guides No garden? What to do with your bokashi and Bokashi and garden compost.

In summary

Fermented bokashi is a pre-compost: it is the soil that turns it into earth. Bury it 20 to 30 cm deep, preferably in a trench, well mixed with 2 or 3 times its volume of soil and around thirty centimetres from roots. Wait at least two weeks before planting, ideally three to four, longer if the soil is cold. In the vegetable garden, set up a bed rotation; around trees, dig beyond the edge of the canopy. And never leave it on the surface.

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Other topics in the guide

Vermicomposting30 sheets →Composting25 sheets →EM micro-organisms26 sheets →