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What is PA Yeomans Keyline System?

The Keyline System was developed by PA Yeomans in the early 1940s to aid:

  • comprehensive whole farm design
  • contour cultivation
  • water storage in farm dams
  • better farm road layout
  • quick gravity powered irrigation
  •  contour strip forests
  • subdivision
  • healing erosion
  • solving salinity

PA Yeomans’ philosophy was that permanent agriculture must materially benefit the farmer and the land.

Properties with a Keyline Design are rendered substantially drought proof for 5 years. Any small rainfall during the drought is efficiently used to extend the drought protection.

Keyline is an ordered set of principles, techniques and systems.

When fully utilised, Keyline Design produces strategies and tactics to develop the natural or existing landscape through regeneration and enhancement.

Keyline Designs

Table of Contents

Who was PA Yeomans?

PA Yeomans (1905 – 1984) was a businessman,  mining assayer and engineer turned grazier. He developed a reputation for honesty in an industry fraught with charlatans and corruption as a good assay of gold and tin.

After purchasing a thousand acres of poor land 40 miles west of Sydney, he realised that nobody in agriculture was even aware of the importance of soil life.

Water doctrine was created by the US Corps of Engineers whose purpose was to move troops over land efficiently and so drain any water out of the way as quickly as possible. Saving water for later use was not even considered. The military are not in the agriculture business.

Unfortunately, this shortsighted approach was worshipped by the government of the time (even today). He spent the remainder of his life trying to correct this unmitigated stupidity which did not make him a popular man with many – no statues here.

As a thinking man, he immediately set to researching and designing possible solutions.

If you treat nature with respect, she will tell you her secrets.

PA Yeomans

The Origin of Keyline

The Keyline System was a journey over years. It did nor arrive full blown.

After the death of his brother in law who was managing his property, PA as he was known, took over the management. He rapidly realised that property management methods of the time were inefficient and destructive.

His block had shallow soil over shale rock and as a result of rampant erosion was infertile and poorly watered – a real battler’s block.

Having been a professional mining engineer, he was familiar with managing water flow in the landscape. He sought a way to improve the fertility and usefulness of his land.

He immediately addressed the erosion as the waste of precious soil which deeply offended him both professionally and personally.

His next step was to rip the soft shale in an attempt to increase the soil depth. He discovered the Keyline point where the fall of the slope changed when determining how high on the slope to rip. He drew a line on contour through this point and called it the Keyline.

His tool of choice to break up the shale was a deep ripping plough similar to a heavy chisel plough.

He noticed that when he ripped parallel to the Keyline to avoid erosion, that the plough line often deviated to below the contour due to features of the landscape. Later he noticed that where the line was ripped below contour, water was being directed from the wetter gullies out to the dry ridges.

This was a real bonus as it brought ridge country into production.

He quickly modified his systems to include ripping on a falling line below the contour. This improved his prior discovery and granted him better use of his landscape.

Next followed a series of modifications to his plough to minimise disturbance to the topsoil, but to shatter the subsoil and bedrock. The result is the current Yeomans plough. This plough created greater topsoil depth and improved water dispersion by slowing, soaking and storing runoff.

Having improved his water retention, he turned his attention to improving the performance of the land.

The key aspect was still water. Undulating country does not lend itself to traditional irrigation. He developed a system of catchment ditches on contour which linked storage dams. This stored water for later use. He needed an easy system to deliver it to his slopes.

To avoid pumping over the dam wall he used a lock pipe through the bottom of the dam wall and protected it with baffles. This enabled him to direct water via a channel enabling flood irrigation.

The final component of his system involved mixing his pasture species to use selected legumes to provide ground cover and assist the growth of his pasture and grain crops.

What does Keyline Cover?

  • Erosion Management
  • Water Management
  • Short Duration Flood Irrigation
  • Pasture Management


The Ethics of Keyline Design

Keyline ethics revolve around care for the land and common sense.

They are best described as “Do No Harm” and “Leave it better than you found it,

Keyline Design Tools

  • Scale of Permanence
  • Keyline contour as the focus of the design
  • Linked dams on contour
  • Irrigation ditches

Scale of Permanence 

Yoemans developed a Scale of Permanence for the land. From the most permanent, to the least was:

  1. Climate
  2. Land-form
  3. Water Supply
  4. Roads and Access
  5. Trees
  6. Structures
  7. Fences
  8. Soil

The scale is accurate. Mountains can be moved, but it is rare and expensive. Roads usually outlast Trees – look at the Roman roads. Trees regularly outlast sheds and fences. Soil can be modified within one to three years.

When making long term plans, consider this scale the best guide available and address each level in top down order either as a constraint or modification.

Keyline Management tools

  • Surveying for level
  • Yeomans ploughing
  • Grain / legume companion planting
  • Short duration flood irrigation

Plan the work then work the plan.
P.A. Yeomans

Find the Keyline

There is a point in the slope of a valley where the shape of the ground changes from convex to concave – most easily identified by your heels as you are walking directly downhill. This is the key point.

A line on contour passing through the key point is called the keyline. This line should be marked in the landscape, usually by a row of trees, a road or a water collection ditch between dams.

The keypoint will also usually indicate the high water mark for the highest dam site on the slope.

Keyline Ploughing

The main feature of a Yeomans’ Keyline Plough is that it does not greatly disturb the topsoil zone and its micro-life. In particular, this retains the mycelial network which feeds the root network of trees and pasture.

When the land is ripped slightly below contour using a Keyline Plough, water is encouraged to travel from the valley bottom to the ridge line. This enables the normally dry ridges to produce better pasture.

Another benefit of Keyline Ploughing is to increase the depth of the soil. Normally an area is ploughed each year for three years, increasing the soil depth and allowing water and air to infiltrate. The newly opened subsoil is thus activated allowing colonisation by soil micro-life.

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