What it solves
Water concentrates in valleys. Ridges go dry.
Over years, valleys cut gullies and ridges lose topsoil. The land splits into a wet half and a thirsty one.
Pumps and pipes fight that pattern with horsepower. Keyline reads it and reroutes water using gravity alone.
P.A. Yeomans worked it out on his land outside Sydney in the 1950s. Results show up fast: more even soil moisture, topsoil built in years not centuries, less erosion, more stock per hectare. Pairs cleanly with swales and rainwater harvesting.
Find the keyline
Walk up a valley from the bottom. Watch the ground.
Where the floor stops being a tight channel and opens into a broader form, that is the key point. Follow that elevation laterally across the slope. That contour is the keyline.
Every valley has one. Every ridge has its mirror.
It is the leverage point. Rip parallel to it but drift slightly off-contour, away from the valley, and each furrow carries water a few meters further toward the dry ridge. One furrow does little. A hundred furrows redistribute the whole hillside.
An A-frame level works. A laser is faster.
Rip it in
The tool is a single-tine subsoil plough. A Yeomans or Wallace ripper cuts 30 to 45 cm deep without inverting the soil.
That depth matters. You are slotting compacted subsoil so air and water move through it, not flipping topsoil or shredding fungal hyphae the way a disc or rotary does.
The pattern is the trick. In valleys, rip lines drift downhill toward the ridges. On ridges, lines drift uphill toward the valleys. Always slightly off-contour. Every rip becomes a small lateral channel.
Time the pass for just before the wet season. The first rain fills the new slots and trains the soil to drink that way. Grass closes over the lines in two to four weeks. The slots keep working underground for years.
Re-rip every one to two years, a little deeper each pass.
Where it sits in the plan
Keyline is one layer in a system. Yeomans ranked landscape elements by permanence: climate, landform, water, roads, trees, buildings, fences, soil. Durable stuff gets decided first.
Water sits third. Dams, channels, and rip patterns get drawn before you site a single tree.
That means a dam at the key point of each valley, ridge plantings and contour tree lines, grazing that lets pasture rest between rips. Geoff Lawton stitches keyline into food forest design on land too dry for production without it.
No pumps. No power bill.
When it goes wrong
Wrong tool. A disc cut to "keyline depth" destroys structure and leaves a compacted pan two seasons on. Use a single-tine ripper.
Wrong line. Rip true contour and water stays in the valley. Drift too steep and your rip lines erode out. Aim for a fall around 1 in 400.
Wrong timing. Bone-dry summer ground shatters and burns diesel. Waterlogged ground smears the slot walls shut. Hit it when the profile is moist but firm.
Wrong scale. One paddock of keyline beside a bare compacted neighbour will fill, then overflow. Plan whole catchments.
See also
- Swales on Contour
- Rainwater Harvesting Basics
- Food Forest Design
- Reforestation Techniques
- Ponds and Dams
- Geoff Lawton