01Taking a good sample
Twelve cores, one bag.
A test is only as good as the bag that reaches the bench. Walk the bed in a W, take a core at each of twelve marks, mix them in a clean bucket and send about 500 g. That is the whole method. The rest of this page is the detail.
Post it Monday to Wednesday from anywhere in the Netherlands or Belgium, or bring it to the lab door in Wageningen by 15:00, Friday by 12:00.
02Tools
A trowel, a bucket, a bag and a marker
Nothing here needs buying specially. What matters is that every piece is clean, and that none of it has ever held fertiliser, lime or wood ash.
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Stainless trowel or narrow hand auger
An auger with a 2-3 cm bore gives the neatest cores. A stainless trowel works just as well: dig a slot to 20 cm, then shave a thin slice from one wall the full depth, so the top and the bottom of the layer are both in the core and not only the loose crumb from the surface.
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Clean plastic bucket
This is where the twelve cores meet. Rinse it, let it dry, then break the cores up in it with your hands, pick out stones and roots, and keep mixing until it looks like one soil rather than twelve.
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Freezer bag
A new one with a zip. 500 g of soil is about two mugfuls from the mixed bucket. Squeeze the air out and seal it. There is no need to dry it first; I air dry every sample on the bench at 30 degrees anyway.
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Waterproof marker
Write on the bag itself, never on a paper tag tucked inside. Damp soil turns paper to pulp in two days, and an unnamed bag of brown soil looks exactly like every other one on the shelf.
03Depth and timing
Dig to the depth the roots use, in the quiet months
The two best windows are February to April and September to November. Sample before you feed, not after, and leave a frozen or waterlogged bed alone.
Best months to sample
- JanCold
- FebGood
- MarGood
- AprGood
- MayLate
- JunCrop
- JulCrop
- AugDry
- SepGood
- OctGood
- NovGood
- DecShut
Spring gives you the report before sowing. Autumn gives lime and compost the winter to work in. The bench is busiest February to April at about 60 samples a week, so book a sampling visit two weeks ahead then. The lab is shut from 20 December to 4 January.
- Vegetable beds
- 0-20 cmMost vegetable roots feed in the top 20 cm, and that is the layer you dig and feed. The kilograms per 100 square metres in your report assume this depth, so cores from deeper read low and a scrape of the top 5 cm reads higher than the bed really is.
- Under grass paths
- 0-10 cmUnder turf the nutrients sit close to the surface. Cut back the green and the thatch with the trowel and take the soil beneath it, and keep path cores in their own bag, apart from the beds.
- After lime, manure or fertiliser
- Wait six weeksAnything spread recently has not settled into the soil yet. A sample taken the week after a barrow of manure tells you about the manure, not the bed.
- Ground conditions
- Not frozen, not waterloggedFrozen cores break unevenly and wet ones smear down the trowel. If water stands in the slot you dug, give the bed a dry week and try again.
04Soil texture by feel
Push out a ribbon and see where it breaks
Texture changes over decades, so you only need to find it once. It tells you how a bed holds water and feed, and it is why the same barrow of compost suits one plot and smothers the next.
- Take a walnut of soil from below the top 5 cm and pick out stones and roots.
- Wet it a drop at a time and knead it until it feels like putty and stops taking up water.
- Press it out between thumb and forefinger into a flat ribbon, letting it hang over your finger until it breaks under its own weight.
- Measure the ribbon against a ruler, then rub a wet pinch in your palm: gritty means sand, silky means silt, sticky means clay.
The market garden panel at €74 includes texture by feel and by sedimentation, done on the bench, so you never need to do this before sending a bag. It is simply good to know your own ground.
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Texture 01Clay 0-10%
Sand
0 mm · no ribbon
Gritty and loose. Will not hold a ball even when moist. Drains in an afternoon and loses feed just as quickly, so little and often suits it.
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Texture 02Clay 0-15%
Loamy sand
About 5 mm · crumbles
Holds a weak ball that falls apart as soon as you push it. Gritty, and leaves a faint stain on the fingers. Warms early in spring and dries out by June.
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Texture 03Clay 0-20%
Sandy loam
About 15 mm · cracks early
A short ribbon that cracks almost as soon as it leaves the thumb. Gritty but with some body. The most forgiving soil for a mixed vegetable plot.
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Texture 04Clay 0-27%
Silt loam
About 20 mm · flakes
Smooth and silky like flour, with a ribbon that flakes at the edges rather than bending. Common on the river ground along the Rhine. Forms a crust after heavy rain.
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Texture 05Clay 27-40%
Clay loam
About 40 mm · droops, then breaks
Sticky with some grit, and takes a faint polish under the thumb. Holds feed well but needs compost worked in every year to stay open and drain.
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Texture 06Clay over 40%
Clay
65 mm or more · bends first
A long, shiny, flexible ribbon that bends well before it breaks. Slow to warm, holds water through a dry summer, and sets like brick if dug while wet.
05Compost samples
A litre from five places, including the middle
A heap is never one material. A litre from one spade in the side tells me about the side, and the seedlings you sow into it will meet all of it.
The outside of a heap dries out and stays coarse. The middle runs warm and finishes first. The bottom can sit wet for months. That is why compost that looks finished on the surface can still burn a tray of seedlings.
Take at least five scoops: two low on the sides, two higher up, and one from the middle. Reaching the middle means opening the heap with a fork or digging in until your arm is in to the elbow. Mix the five in the clean bucket and fill a freezer bag with one litre, about four mugfuls.
Leave out anything you can still recognise: a stalk, a corn cob, a curl of eggshell. Those are not compost yet, and a single cob in the respiration jar keeps the reading high for all 72 hours. Plastic, glass and stones you leave in, because the sieve count is part of the test.
As with soil, there is no need to dry it. Send it as it comes off the heap.
- Amount
- 1 litreFrom at least five places, mixed before bagging.
- The test
- €62 · 10 working daysRespiration over 72 hours, a 7 day cress germination and root count, carbon to nitrogen ratio, pH, conductivity, moisture and a sieve count of plastic, glass and stones.
06Labelling and posting
Name, bed and date, then post it early in the week
Turnaround runs from the working day the bag arrives: 5 working days for the basic check, 8 for the market garden panel, 10 for compost.
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Write on the bag
Your name, the bed name and the date, in waterproof marker on the bag itself. Sending several beds? Give each one a name you will recognise when the report comes back in the post.
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Post Monday to Wednesday
From anywhere in the Netherlands or Belgium. A bag posted on a Thursday can spend the weekend in a warm depot, and soil keeps changing inside a sealed bag. Slip it into a second bag or a small box for the journey.
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Or bring it to the lab door
Drop-offs come to the lab door in Wageningen between 08:30 and 15:00, Monday to Thursday, and until 12:00 on Friday. Closed weekends and Dutch public holidays.
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Say it is coming
Write to hello@biotova.com with how many bags and which test. Femke replies the same working day with posting or drop-off details. One bag is a normal job. Under 20 samples nothing is paid until the report arrives with its transfer slip; batches of 20 or more pay 25% when the bags arrive.