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BIOTOVA

00Soil and compost testing for market gardeners and allotment holders

Send us a bag of soil. Get back a plain answer.

A small lab in Wageningen. This is how a job runs.

Tests and prices from €38
Fig. 1 · Gouge core Depth in cm The same 30 centimetre soil core laid on its side, with the 20 cm cut line marked in coral 0 5 10 15 20 25 30 CM TOPSOIL 20 CM SUBSOIL
Twelve of these per bed. Only the top 20 cm goes in the bucket. The coral line is where the core is cut.
  1. 01 Day 0 Dig
  2. 02 Day 0 Bag and label
  3. 03 Day 1 Drop off or post
  4. 04 Days 2 to 9 On the bench
  5. 05 When ready Read the report

01Five steps, one bag

How a job runs

I spent years running soil analyses for field trials before I started testing allotment soil for neighbours in 2018. The method hasn't changed much since. Here is each step, who does it, and why it's there.

  1. 01

    Dig

    Day 0

    What you do

    Walk the bed in a W and push a trowel or narrow auger in at 12 points, 0 to 20 cm deep. Tip every core into one clean plastic bucket and mix it well by hand.

    Why twelve and not three? One bed varies more than you'd think: the corner where the heap stood, the strip the hose always floods. Three cores can land on any of those. Twelve, mixed, describe the bed you actually plant.

    What we do

    Nothing yet, unless you'd rather I dug. Sampling visits run on Tuesdays and Thursdays within 25 km of the lab, €45 for up to 8 beds plus the test fees.

    The full sampling method is on its own page.

  2. 02

    Bag and label

    Day 0

    What you do

    Take about 500 g from the bucket, two mugfuls, and put it in a freezer bag. Write your name, the bed name and the date on the bag in waterproof marker. Don't dry it first. For compost, send a litre.

    What we do

    Every bag gets a sample number the minute it comes through the door, and that number follows it all the way to the report. Writing on the bag itself, not on a slip inside, is what stops two beds both called "the back one" from ever being swapped.

  3. 03

    Drop off or post

    Day 1

    What you do

    Post it Monday to Wednesday from anywhere in the Netherlands or Belgium, or bring it to the lab door until 15:00 Monday to Thursday and until 12:00 on Friday. Send a line to hello@biotova.com first so I know it's coming.

    What we do

    The clock starts on the working day the bag arrives. I ask for early-week posting because soil left in a warm depot over a weekend keeps living in its bag, and the nitrate figure on Monday morning is no longer the one in your bed.

  4. 04

    On the bench

    Days 2 to 9

    What you do

    Nothing. This is the part where you wait, and I'd rather it took a day longer than came back wrong.

    A basic check takes 5 working days, the market garden panel 8 and the compost test 10. The metals screen adds one day.

    What we do

    The soil goes onto a tray and air dries at 30 degrees. Any hotter and the organic matter starts to change and potassium reads high, so I keep it gentle even when a wet clay takes two days. Then it's crushed and sieved to 2 mm, because every method is set up for fine earth, not for stones and bits of root.

    Phosphorus extracts are shaken in the afternoon and read the next morning. The blue colour needs time to settle, and reading every batch at the same point is what lets this year's figure sit honestly next to last year's.

  5. 05

    Read the report

    When ready

    What you do

    Two printed pages come by post, or you collect them from the lab. Recommendations are in kilograms per 100 square metres, so you can weigh them out on a kitchen scale. A bank transfer slip is tucked in, payable within 14 days.

    What we do

    I read every report through and write in the margin by hand. Usually it's one thing to change this season and one thing to leave alone. Plenty of beds are over-limed or over-fed, and the most useful note I write is often: nothing needed here this year.

Sample report · page 1 of 2No. 468
Excerpt from report 468, an allotment onion bed in Wageningen
ReadingResultRange for vegThis season
pH6.26.0-6.8Leave
Organic matter5.8 %4-8 %Leave
Phosphorus29 mg/kg20-40Leave
Potassium95 mg/kg120-1801.2 kg per 100 m²
Magnesium70 mg/kg60-100Leave
Onions are greedy for potash and this bed is a little short. Sulphate of potash, 1.2 kg per 100 m², raked in before planting. Everything else: leave well alone. M.

02Nine bags, names left off

On the bench this month

The colour chip is what the dry sample looks like against the soil colour chart. The last line on each card is the sentence that went in the report.

Scroll sideways · readings in mono, as on the bench sheet

  1. No. 418Panel

    Bennekom

    Market garden · leeks and brassicas

    Very dark greyish brown10YR 3/2
    pH
    6.4
    EC
    0.21 mS/cm
    OM
    6.8 %
    P
    38 mg/kg
    K
    78 mg/kg
    Mg
    95 mg/kg

    In the reportNo lime this year. Sulphate of potash, 1.5 kg per 100 m², before the leeks go in.

  2. No. 423Basic

    Ede

    Allotment · potatoes and beans

    Dark brown10YR 3/3
    pH
    5.6
    EC
    0.12 mS/cm
    OM
    4.1 %
    P
    22 mg/kg
    K
    130 mg/kg
    Mg
    60 mg/kg

    In the reportGround limestone at 4 kg per 100 m² this autumn. Not in spring, not before the potatoes.

  3. No. 431Basic

    Wijk bij Duurstede

    Community orchard · currants underneath

    Dark greyish brown10YR 4/2
    pH
    7.3
    EC
    0.18 mS/cm
    OM
    3.9 %
    P
    41 mg/kg
    K
    210 mg/kg
    Mg
    140 mg/kg

    In the reportGood river clay. Leave it alone, mulch the currants and test again in two years.

  4. No. 437Panel

    Renkum

    Community plot · salads all year

    Black10YR 2/1
    pH
    6.9
    EC
    0.58 mS/cm
    OM
    11.2 %
    P
    96 mg/kg
    K
    260 mg/kg
    Mg
    130 mg/kg

    In the reportPhosphate is very high. No manure or chicken pellets here for at least two seasons.

  5. No. 442Basic

    Veenendaal

    Raised beds · mixed vegetables

    Very dark brown10YR 2/2
    pH
    6.1
    EC
    0.32 mS/cm
    OM
    14.5 %
    P
    58 mg/kg
    K
    180 mg/kg
    Mg
    48 mg/kg

    In the reportMagnesium is low for this much organic matter. Kieserite at 2 kg per 100 m² in March.

  6. No. 450Basic

    Arnhem

    Allotment · new plot on old lawn

    Dark yellowish brown10YR 4/4
    pH
    5.9
    EC
    0.09 mS/cm
    OM
    3.2 %
    P
    14 mg/kg
    K
    70 mg/kg
    Mg
    55 mg/kg

    In the reportA hungry soil. Dig in 300 kg well rotted compost per 100 m² and re-test next spring.

  7. No. 456Panel

    Rhenen

    Market garden · tomatoes under a tunnel

    Brown7.5YR 4/3
    pH
    7.0
    EC
    1.42 mS/cm
    OM
    5.5 %
    P
    74 mg/kg
    K
    340 mg/kg
    Mg
    160 mg/kg

    In the reportSalts are building up under cover. Water the beds right through this winter and halve the feed.

  8. No. 461Basic

    Doorwerth

    School garden · runner beans

    Dark greyish brown2.5Y 4/2
    pH
    6.6
    EC
    0.20 mS/cm
    OM
    5.0 %
    P
    33 mg/kg
    K
    140 mg/kg
    Mg
    90 mg/kg

    In the reportA balanced bed. Nothing to add this season. Keep doing what you're doing.

  9. No. 468Basic

    Wageningen

    Allotment · onions and shallots

    Very dark greyish brown10YR 3/2
    pH
    6.2
    EC
    0.15 mS/cm
    OM
    5.8 %
    P
    29 mg/kg
    K
    95 mg/kg
    Mg
    70 mg/kg

    In the reportPotassium on the low side for onions. Sulphate of potash, 1.2 kg per 100 m².

03Prices per sample

What we test

Three tests cover nearly everything that comes through the door. Each price is per sample, includes the printed report with my notes, and is what you pay. No minimum order: one bag is a normal job.

Soil

Basic soil check

€38per sample

pH, electrical conductivity, organic matter by loss on ignition, and plant-available phosphorus, potassium and magnesium. The right test for most allotment beds.

5 working days500 g of soil

Soil

Market garden panel

€74per sample

Everything in the basic check, plus nitrate and ammonium, calcium, sodium, the carbon to nitrogen ratio, and texture by feel and by sedimentation. For beds that crop hard all year.

8 working days500 g of soil

Compost

Compost maturity test

€62per sample

72 hour respiration, a 7 day cress germination and root length count, carbon to nitrogen ratio, pH, conductivity, moisture, and a sieve count of plastic, glass and stones.

10 working days1 litre of compost
Every test, add-on and visit

Metals screen €45 on any soil test · re-test of the same bed within 12 months €28 · 15% off batches of 10 or more identical tests

04Spring 2023 · near the Rhine

A job I'm proud of

In spring 2023 the growers on an old brickworks allotment site near the Rhine asked me to test every plot, all 46 of them. Most sites send a handful of bags from their worst beds. These growers wanted the whole site done in one go, the same way, so nobody had to wonder about their own patch.

I walked it over three Tuesdays with a hand auger and a crate of numbered bags. Twelve cores a plot, 552 cores in all, and every plot ran through the market garden panel with the metals screen added. The screen is a growing guide, not a legal report, and a growing guide was exactly what they needed.

Forty-three plots came back the way you'd hope from ground that has been dug for decades: a bit too much phosphate here, a few that wanted lime there. Three did not. The plots along the old kiln wall showed lead well above what I'd want under vegetables, which made sense once someone remembered where the ash from the kilns used to be tipped.

Those three moved to raised beds with imported soil and a membrane underneath, and they grow salads and beans in them now. The other 43 kept growing exactly as they had. Nobody had to stop, and nobody had to guess. If anyone asks me what a small lab is for, that's the job I'd point to.

Femke

Fig. 2 · Site plan 46 plots Plan of the 46 allotment plots, with plots 3, 4 and 5 along the old kiln wall hatched and holding raised beds HEDGE OLD KILN WALL MAIN PATH SHED 12345678 910111213141516 1718192021222324 2526272829303132 3334353637383940 414243444546 RIVER SIDE RAISED BEDS
Plots 3, 4 and 5 sat against the old kiln wall. They now grow in raised beds on imported soil. The other 43 carry on as before.

05Hours and the winter break

Winter closure and hours

Shut 20 December to 4 January

We shut from 20 December to 4 January. The ground is usually frozen or soaked by then anyway, and I would much rather you sampled in February.

Anything that turns up in the post that fortnight goes in the cold room and is the first thing on the bench on the 5th.

Femke

Every week

  • Monday to Thursday08:30-16:30
  • Friday08:30-12:30

Samples received

Until 15:00 Monday to Thursday and until 12:00 on Friday. Closed weekends and Dutch public holidays.

In spring

The bench takes about 60 samples a week and fills up between February and April. Book sampling visits at least two weeks ahead.