Open ground and hold fertility

Turn wild land into a field that does not lose its fertility in five years.

Tier 1 · Neolithic Food t1-clear Blocked by prerequisites

**Burnt clearing in northern Thailand — ground opened, and fertility released in one go.** An example of slash and burn agriculture practice Thailand · 2009-03-18 13:55 · mattmangum · CC BY 2.0 · Commons ↗

Everything for this step

Field guide: Micro-organisms → 6 sections The sciences → 15 sections Soils and plant nutrition → 4 sections Seeds and the growing year → 5 sections Sustainable farming → 9 sections
Builds: Twin-vault composting latrine
Reference sheets: 1 sheet in Sustainable farming
Sciences it rests on: Agricultural science · Ecology · Chemistry
Books: 5 sources under Read this ↓
Track: Crops and soil, level 2 of 7 · next: Plant staples

Why this matters

Clearing is easy; keeping the ground productive afterwards is the actual skill. Slash-and-burn gives one spectacular harvest from the ash and then a decline. Societies that never solved fertility maintenance moved every few years and never built anything permanent.

The shape of it

Choose ground by soil, not by convenience: deep, dark, crumbly, well-drained, on a gentle slope. Dig a pit and look at the profile before committing a season to it.
Clear by girdling large trees a year ahead — ring the bark and let them die standing — then fell, burn the brush and spread the ash. Ash is potash and lime and is worth spreading deliberately, not just leaving where it burnt.
Fertility is a balance sheet. Every harvest removes nitrogen, phosphorus and potassium from the field. If you do not return them, yields decline year on year regardless of how hard you work.
Return everything organic: manure, bedding, crop residues, ash, kitchen waste, composted humanure (Humanure Handbook), bones burnt and crushed for phosphate.
Rotate with legumes. Beans, peas, clover, vetch and lupins fix atmospheric nitrogen through root bacteria. A four-course rotation — a cereal, a root crop, a cereal, then a legume ley — was the innovation that doubled European yields, and it costs you nothing but discipline.
Never leave soil bare over winter on a slope. A cover crop or a mulch is the difference between soil and a gully.
Terrace or contour-plough anything steep. Erosion is irreversible on any timescale you care about — a centimetre of topsoil takes centuries to form and one storm to remove.

Working across the slope, in section Fig 1

Earth / subsoilMasonry / brick

On gentle ground, ridges along the contour hold the rain where it falls and residue keeps the surface covered. A grass strip on the contour catches what moves. On steep ground, level benches held by stone walls replace the slope entirely.

Doing it, step by step

The summary above says what has to happen. This says how, with the numbers that decide whether it works.

1 · Read the soil profile before committing a season to a field

Dig a pit at least 60 cm deep in the candidate ground and look at the face:

Depth of the dark topsoil. Under 10 cm is thin ground that will not take continuous cropping.
Structure — crumbly is good, a solid block or a compacted pan is not.
Drainage — grey or blue-grey mottling means water sits there for part of the year.
Stones and roots — how much work the first ploughing will be.
Texture, by the jar test: shake soil in water and let it settle. Sand drops in a minute, silt in an hour, clay over a day.

Choose deep, dark, crumbly, well-drained ground on a gentle slope, and reject convenience as a reason.

✓ Check: A pit has been dug and described for each candidate field, and the chosen field has the deepest topsoil of those looked at.

2 · Clear in the right order and keep the ash

Girdle large trees a full year ahead — ring the bark through to the sapwood and let them die standing. They dry, drop their leaves, and are far easier and safer to fell the following year. See wood and the forest for felling safely.

Burn the brush where you want the fertility, and spread the ash deliberately rather than leaving it in heaps: ash is potash and lime, it raises pH on acid ground, and a heap of it scorches one patch while the rest of the field gets nothing.

Leave stumps to rot rather than hauling them out by hand; plough around them for the first years.

✓ Check: Ash from every burn has been spread across the field rather than left in heaps, and no standing dead tree remains where it could fall on the working ground.

3 · Treat fertility as a balance sheet, because it is one

Every harvest removes nitrogen, phosphorus and potassium from the field and carries them to the settlement. If they are not returned, yields fall year on year no matter how hard the ground is worked — and the fall is slow enough that it is blamed on weather for a decade.

What comes back:

Manure and bedding — the single largest flow, and the reason livestock and fields belong together.
Crop residues — straw, haulm, leaves, ploughed in or composted.
Ash — potash and lime.
Bones, burnt and crushed, for phosphate.
Composted human waste, treated properly — see separating waste from water and the sanitation guide.

Write down what leaves the field and what returns to it. A balance sheet nobody keeps is a balance sheet in deficit.

✓ Check: Manure, residues and ash are all being returned to the fields systematically, and the group can say roughly what proportion of each harvest's residue goes back.

4 · Rotate, with a legume in the rotation

Legumes fix nitrogen from the air through bacteria in their root nodules — clover, vetch, beans, peas, lupins — and they fix about 30–40 kg of nitrogen for every tonne of dry top growth, roots included, so a good legume ley can add on the order of 50–200 kg of nitrogen per hectare per year without a sack of anything being carried in. The field gets most of it when the ley is left there; harvesting the seed or carrying off the straw takes much of it away.

A four-course rotation that has worked for centuries: cereal → root crop → cereal → legume ley. The root crop is weeded hard, which cleans the ground; the ley rests and feeds it.

Do not follow a crop with itself, or with another of the same family: tomato, potato and pepper share their soil-borne diseases, as do cabbage, turnip and mustard. Rotation also breaks the pest and disease cycles that build up under a repeated crop, which is half of its value.

✓ Check: Every field has a written rotation with a legume in it, and no field has carried the same crop two years running.

5 · Never leave soil bare on a slope

Bare soil over winter on any slope is not soil for long. A cover crop — rye, vetch, mustard — or a mulch of straw or leaves is the difference between a field and a gully.

Erosion is effectively irreversible: a centimetre of topsoil takes centuries to form and one storm to remove. The damage is also invisible while it happens, appearing as a slow yield decline and a muddier stream after rain — watch the stream after a storm, because that colour is the field leaving.

✓ Check: No field is bare through the wet season, and the stream below the fields does not run noticeably browner than upstream after rain.

6 · Work across the slope, not up and down it

Plough, sow and hoe along the contour. A furrow running up and down a slope is a purpose-built drainage channel for your own topsoil.

On anything steep, terrace: level benches held by stone walls or grass banks, built downhill first so the spoil from each supports the one below. It is enormous work and it is permanent — terraces built two thousand years ago are still being farmed.

Plant hedges, grass strips or tree lines along the contour as a cheaper intermediate: they slow water, catch soil, and become terraces on their own over decades.

✓ Check: All cultivation runs along the contour, and after heavy rain there are no rills or channels cut into any field.

7 · Clear only what you can actually keep

Clearing is the easy part. Weeding, manuring and harvesting are what limit a group, and a field cleared beyond that limit grows weeds, exports fertility and returns nothing.

A rough planning figure: hand cultivation supports roughly 0.1–0.2 hectares per person of intensively worked ground, more with draft animals. Start below the limit, prove you can keep it, and expand only after a season in which everything was weeded on time.

✓ Check: Every cleared field was fully weeded during the critical early weeks of the last season — and if one was not, no new ground is cleared this year.

8 · Watch the oldest field, because it tells you first

The field cleared first is the one where declining fertility shows first. Record yield per area on it every year, in whatever unit is repeatable — baskets, sheaves, weight.

Three consecutive harvests without decline means the system is in balance. A steady fall means the balance sheet is in deficit: more legume, more manure, longer ley, or take the field out of production for a season. Do not respond by clearing more ground — that exports the problem and doubles the work.

✓ Check: Yields on the oldest field have been recorded for at least three harvests and are not declining.

Build it

Dimensioned drawings, bills of materials and construction procedures for the things this step asks for.

BUILD · Easy to build, requires discipline to run

Twin-vault composting latrine

Break the faecal–oral route and return the nutrients — the highest lives-saved-per-effort structure a settlement can build.

8–12 person-dayscrew 3

The better path

What the record shows was done at this step, what to do instead at this tier, and the evidence. All of them: the better path.

Adopt earlier

Plant through the residue instead of ploughing the ground bare

What was done: For most of farming's history the ground was ploughed bare, burned, or left in bare fallow; the plough became the picture of farming itself.
Do instead: Keep at least 30 % of the soil covered with residue, mulch or a cover crop, open the ground only where the seed goes — a pointed planting stick makes the hole — and grow at least three different crops in sequence.
Evidence: These are the three principles by which FAO defines conservation agriculture: minimum soil disturbance, permanent organic cover of at least 30 %, and diversification across at least three crops. The cost of the alternative is on record: the Dust Bowl of the 1930s blew the topsoil off ploughed grassland across the southern Great Plains, and the United States founded its Soil Conservation Service in 1935 in response.

Needs nothing that is not already in hand.

Adopt earlier

Compost hot before it goes on food crops

What was done: Raw manure and night soil have been spread straight onto fields for as long as there have been fields, carrying the pathogens in them onto the food.
Do instead: Build the pile at a carbon-to-nitrogen ratio near 30:1, keep it as damp as a wrung-out sponge, and hold it at 55 °C or more for at least 15 days, turning it at least five times, before it goes near a crop that is eaten raw.
Evidence: 55 °C for 15 days with five turnings is the US EPA's standard for a windrow compost that has been treated to kill pathogens (40 CFR 503, Appendix B). A starting mix of 25:1 to 40:1 is the USDA NRCS composting standard; Cornell puts the ideal near 30:1.

Needs: Separate waste from water

How this fails

Continuous cereal cropping with no legume and no manure. Yields fall roughly by half within a decade and the ground takes a generation to recover.

Ploughing straight up and down a slope, which builds a drainage channel for your own topsoil.

Clearing far more ground than the group can actually keep weeded and manured.

Burning brush and letting the ash blow away.

How you know it worked

VerificationYields on the oldest field have not declined over three consecutive harvests.

What this unlocks

t1-staples

Plant staples

Grow enough storable calories to stop foraging.

t1-property

Boundary and tenure

Establish who holds which ground, in a form that outlives the argument.

t3-rotation

The four-course rotation, field drains and the seed drill

Run the fields as one system: a rotation whose fodder crops feed the stock and whose manure feeds the grain, wet land underdrained so it can be worked and sown, and grain drilled in rows at a known rate and depth so it can be counted and hoed.