Keyline History, Concepts & Geometry
1. Keyline Design history
The central idea behind ‘Keyline’ water management is to consciously slow, sink and spread rainwater by relieving compaction, opening up pore space in compacted soil and distributing excess water towards drier parts of the landscape. This has the effect of buffering the natural concentration of water towards valleys and reducing flooding.
By maximizing the flow of water to drier ridges (using precise plow lines or mounds that fall slightly off contour), we can infiltrate it across the broadest possible area. In this respect, keyline strategies can be both a flood and drought mitigation strategy.
‘Keyline’ water management has the potential to enhance the water efficiency of any production system. Applications can include:
- pastured livestock & grass farming
- agro-forestry & forestry layout
- orchard layout
- silvo-pasture layout
- alley cropping layout
- annual vegetable production
- ecological restoration
- watershed planning & management
- urban planning (new developments)
Agriculture and Agri-Food Canada (AAFC) and the BC Ministry of Agriculture are committed to working with industry partners. Opinions expressed in this document are those of Hatchet & Seed and not necessarily those of AAFC, the Ministry of Agriculture or the Investment Agriculture Foundation.
1. Keyline Design History
Keyline design was first developed in the late 1940's by Australian mining geologist and engineer P. A. Yeomans. He developed several farm properties with the goal of flood and drought proofing them. His focus was on accelerating the formation of topsoil by improving the soil penetration of oxygen, water and plant roots.
His concepts are best described in his books:
The Australian Keyline Plan (1954)
The Challenge of Landscape (1958)
Water For Every Farm (1965)
The City Forest (1971)
Keyline design has since been adapted to many different production systems across the globe.
2. What is 'keyline water management'? Why is it important?
Keyline water management is any production system that applies 'keyline geometry' to cultivation patterns with the goal of slowing, sinking, spreading and storing of rainwater. Another main goal is the formation of topsoil as both water storage & fertility mechanisms.
The central idea behind keyline design from a water perspective is to capture water at the highest possible elevation and distribute it outward toward the drier ridges using gravity, slowing the natural concentration of water in valleys. Maximizing the flow of water to the drier ridges using precise plow lines (or mounds) falling slightly off contour slows the movement of water and spreads it more uniformly, infiltrating it across the broadest possible area. It is both a flood and drought mitigation strategy.
While permanent subsurface drains are commonly used for disposing of excess rain in winter, very seldom is there conscious effort to spread that water to areas that do not have the same large catchment area (eg: ridges in the landscape).
Another important facet of keyline design is the establishment of effective water storage ponds on the landscape.
With the threat of extended flooding and drought predicted with climate change, it is becoming even more important to better manage abundant winter rainfall for times of scarcity.
Notice: Only the keyline is purely on contour. The other parallel lines encourage water to shed towards the ridges. This is essence of keyline cultivation - allowing farmers to cultivate in parallel rows (something nearly all farmers do), while optimizing both drainage and water retention.
Photo Source: Water for Every Farm. P.A. Yeoman. 1968.
3. What is ‘keyline pattern cultivation'?
‘Keyline pattern cultivation' is subsoil ripping done using keyline geometry. It is meant to penetrate the subsoil, to a depth of 2’’ below existing rooting depth without inverting the soil. The cultivation pattern uses keyline geometry to act as a micro-water management storage ditch as well, holding more water on ridges.
The effect is to loosen compacted soil and open up micro-water harvesting & diversion ditches across the landscape. In some pastures, it is possible to increase the rooting depth of forage plants by breaking up hardpan and allowing root access into these micro-furrows.
With water and root activity deeper than before the treatment, the opportunity exists to create carbon storage deeper into the profile via root exudates & soil microorganisms.
To summarize, potential advantages of properly applied keyline pattern cultivation include:
- Increase farm water use efficiency and availability
- Support the capture, storage, and utilization of precipitation
- Reduce nutrient loading into local creeks and near-shore marine environments
- More even distribution of rainfall across the site, reduced flooding and drought risk
- Increased oxygen, nutrient and water infiltration, increasing soil health
- Improved soil structure, tilth & internal drainage
- Fracturing of hardpans creating a deeper rhizosphere and reducing compaction
Potential disadvantages include:
- Added cost of production
- Land too steep for safe tractor use
- Poor timing could open up soil to increased evaporation
- Poor timing could create compaction or tractor tire ruts
- Application of the techniques when not required, such as where soil health and water-holding capacity are already optimized
4. Is there more to keyline design than keyline cultivation?
Yes. Keyline pattern cultivation ('subsoil ripping') is only one technique within the 'Keyline Design' framework. P.A. Yeomans best described this framework in his 1958 book, the Challenge of Landscape, when he originated the 'Keyline Scale of Permanence'.
In order to plan the development and management of land, the many factors that are involved should be related in some logical order. The planning of one aspect cuts across others, so some must have preference. Decisions have to be made on all sorts of apparently conflicting items of land planning. We need also to have an aim or an object, a basic plan.
- P.A. Yeomans, the Challenge of Landscape, Chapter IV
Whole farm planning is an important step before reaching out for any particular 'technique'. There may be instances where effective and efficient water management do not include the need for keyline cultivation.
Many modern practitioners are combining keyline design with other strategies like agro-forestry, silvo-pasture, "Holistic Planned Grazing", and bio-fertilization.
5. Where has this been applied?
‘Keyline subsoil ripping and keyline agro-forestry' have been applied worldwide in all major biomes of the world. It has been applied to many different production systems. The following are a few of many examples:
Photo Source: Darren Doherty.
United States - Wisconsin
United States - Iowa
6. Has this been researched before?
While there are many farmer testimonials about the effectiveness of ‘keyline water management’ in on-line farm forums, studies have been few and far between. Farmers often report better infiltration of runoff, better field retention/ drainage, better penetration of water into subsoil, and improved tree and pasture growth. However, there is little credible data to support or disprove these practices.
Photo Source: Keith Ryans.
There are unpublished reports of some monitoring parameters (like soil organic carbon & rooting depth) increasing greatly. A study mentioned in the On Pasture article "Keyline - Does it Work?" found little to no improvement in soil organic matter. However, the study did not monitor for moisture retention & distribution, a parameter that is central to our project. It was also completed on high quality, grazed pasture in a ‘summer-rain environment’, much different than our climate and soil types. Our monitoring is meant to address the spacial and temporal moisture distribution, both across the landscape and through the seasons.
7. How are soil health, carbon and water management related?
One of the chief aims of keyline farm management is the formation of topsoil. The more organic carbon in the soil, the more water holding capacity the soil has. This chart from Dr. Christine Jones shows the relationship between soil carbon, water stored per hectare and CO2 sequestered per hectare.
Her research shows that for every 1% increase in OC, water storage can increase by up to 144,000 L / ha; that's 58,000 L per acre!
Photo Source: Dr. Christine J0nes.
8. How is a Yeoman Plow different from a typical subsoiler?
Subsoilers have commonly been used in the agricultural, restoration and forestry sectors for breaking up restrictive soil layers. However, they are typically set to go as low as possible on the first pass and require very heavy machinery. The Yeomans Plow is designed to be used as part of 'Keyline Cultivation' to increase root penetration and is typically only set 1-2'' below the existing root layer. As such (and because of its design), it requires less horsepower (HP) to pull than conventional subsoilers.
A Yeomans Plow is specifically designed to:
- minimize surface disturbance and soil profile mixing
- reduce HP requirement compared to other subsoilers with thicker shanks and more blunt points
- allow the attachment of other implements, including seed boxes and liquid fertilizer injection
There are other plows on the market with similar advertised features. They include:
9. How is ‘keyline pattern subsoil ripping’ different than subsoiling on other patterns?
Keyline vs. contour layout
Keyline layout differs from contour planting in that rows remain equidistant from one another. Landscape contours are always irregular and never equidistant. Keyline layout seeks to optimize landform while still maintaining equidistance in cultivation rows so as to maximize density and efficiency. Contour layouts leave irregular shapes that are difficult to maintain.
Keyline vs. grid layout
Most farms and orchards choose grid layout, typically based on the artifical property boundary so as to maximize planting area. That can be the major advantage of 'grid-layout'. However, by ignoring the contours, we also ignore the water and nutrient holding benefits that come with slowing and spreading water.
10. What is 'keyline mound formation'? What are the advantages and disadvantages?
Keyline mounds or berms are planting berms that follow keyline patterning. They can be used for perennial plant crops (trees, shrubs and perennial herbs) or for annual crops.
- Increase loosened topsoil depth available for planting
- Can include water harvesting gutter to slow surface runoff (if any) on keyline pattern
- Can raise trees and shrubs up out of a high winter water table
- Can be combined with subsoil ripping
- Can create permanent access difficulties
- Can create difficult maintenance conditions for tractors and mowers
11. What about small farms where there is no 'classic' keyline, or primary valley or primary ridge?
On farms where no true keyline is available or where there is no access to both a primary valley or primary ridge, 'guidelines' are used.
Based on the topography of the land, cultivation guidelines are chosen by the farmer to achieve desired goals. By using a contour map, guidelines can be set such that all subsequent plow lines achieve the desired goal.
For example, the farmer may wish to divert excess soil moisture in the direction of an irrigation pond, or to an area that will benefit from increased soil moisture later in the season.
12. What are the predicted regional climate effects that might impact water usage, drought and flooding?
In 2012, the Capital Regional District (CRD) was part of a research project with the Pacific Climate Impacts Consortium (PCIC), International Council for Local Environmental Initiatives (ICLEI) Canada and a handful of nearby local governments to develop a regional climate model for the Georgia Basin.
Highlights from the findings include:
- Extreme temperatures (32°C to 35°C) are projected to occur almost four times as often in future in the CRD.
- The amount of precipitation falling during very wet days is projected to increase by 20%, with precipitation during extremely wet days projected to increase by 25% in future in the CRD.
- More extreme precipitation events (3-hour duration) are projected to occur on average three and a half times as often in future in the CRD.
- There will be fewer Heating Degree Days and a substantial increase in Cooling Degree Days in the CRD.