Freshly keyline plowed (Photo: Kirsten Bradley)
Plan the work then work the plan. — P.A. Yeomans
In the mid 1950s, Australian engineer P.A. Yeomans demonstrated a new system of land management he called the Keyline system. The consensus of the time, championed by people like Dr H.H. Bennett, was that soil was a finite resource and that once depleted “it was irretrievably lost as if consumed by fire”. P.A. understood that long natural carbon cycles create soil, but also knew that this process takes hundreds or thousands of years. By adjusting the conditions in the soil with his plowing and management techniques, P.A. was able to speed this process and create dozens of millimeters of fertile topsoil in just one year.
P.A. started out as a conservationist, but quickly realized that creation of topsoil was the ideal solution, while conservation simply delayed the inevitable soil destruction. Depending on the climatological conditions, conservation may ‘work’ for just a few years under harsh conditions, while allowing profitable cropping for decades in other milder regions. This is a direct cause of the extractive farming methods still used today. Farming then and now is still dominated by the practice of mining the topsoil for minerals, turning over the exhausted topsoil with plows, and replenishing the minerals lost in the crop with fertilizers. This, as seen over and over, leads to soil depletion, erosion, and finally desertification.
By changing this method of conservation to one that continually builds soil fertility to feed the crops, the land will become more fertile over time. This creates a feedback loop, but one with positive outcomes. It can be said that one should “feed the soil, not the plants.” When healthy soil is present and maintained, any crops suitable for the region will grow well without any fertilizer. Herein lies P.A.’s argument that soil creation and the Keyline system will lower the costs of the farm while at the same time producing higher yielding, and thus more profitable, harvests. This is even more relevant in today’s profit driven world. Farmers that would not otherwise concern themselves with improving their methods for the sake of the land will more often pursue actions that will increase their bottom lines.
Leveling is the primary concept when dealing with water and the Keyline system. Before any earth is moved the land should be sufficiently surveyed and pegged. Pegging is simply placing pegs at a corresponding level around the property to give rise to a visual level line. By manipulating the techniques used to determine each peg’s placement, one can plan-out all of the features of a system.
While a modern laser level would be the easiest tool to use in leveling, low-tech, do-it-yourself options exist. P.A. designed a type of level called a bunyip. Another DIY level is an A-Frame level. A-frame levels can be constructed even easier than bunyips, requiring only three pieces of wood, a string, and a rock!
Any of these leveling devices will need to be accompanied by a large number of pegs. When the level is found, the pegs can be placed accordingly to map out the land before any work is done. It may be useful to have pegs tall enough to be readily seen over the surrounding vegetation, or the vegetation can be cleared off before the pegs are placed. When using pegs to mark keylines, channels, and dam water levels, it is advisable to have the pegs painted or flagged to distinguish the lines dotting the landscape at a glance.
By using a chisel, tyne, or P.A.’s keyline plow, both aeration and water integration can be accomplished in one pass over the land. While mouldboard type plows turn over just the topsoil, the chisel plow creates numerous deep cuts into the compacted and often sealed soil where air and water can now penetrate deeper and activate the decomposition process just below the topsoil. Different kinds of soil types may require altered preparation. For example, sandy, light soil in arid conditions can be chisel plowed deeply (45 cm) from the very start, while in heavy clay soils you must chisel plow shallowly (8 cm) the first year, while slowly increasing plow depth each year. This is because the heavier soil types will seal over with the first substantial rainfall, locking out the water and air.
The goal of this type of cultivation is to blend the subsoil and topsoil into one contiguous layer. This creates a more balanced distribution of minerals, nutrients, air, and water, everything needed to grow healthy plants. Again, a more traditional turn-plowing would leave the topsoil overturned and segregated from the subsoil leading to soil destruction rather than creation.
To create soil, certain conditions must be met. Some kind of organic material must be present that, when combined with the correct levels of moisture and air, will create an ideal soil climate for decay to occur. While adding organic material is often the fastest way to improve soil condition, over large areas of land it is not practical to haul in the massive amount of materials that would be required. The Keyline system focuses on hastening the decomposition of the naturally occurring organic material already in the soil by adjusting the moisture and air levels within. Once the biotic conditions in the soil are jump-started, micro and macroscopic life return in such abundance that it dwarfs the total weight of a harvested crop or the grazing cows above.
Roots are one of the main organic components that will be decomposing in the midst of the added moisture and air. As soil improves, more plants will grow, from the soil’s seed-bank or from being sown, and increase the field’s biomass; this is another positive feedback loop. Some of these plants are likely to have deep tap roots that stretch down into the subsoil and bring up minerals unlocked by chisel plowing, making them available for plants with shallower roots. As these and other pants die, the roots decay more rapidly in the improved soil conditions. The spaces left behind by the roots create natural pathways for air and water to further integrate into the soil. Even crops grown for harvest or grazing will still leave the roots in the soil, continuing the improvement process.
A positive interaction in soil life that can be used to your advantage is one between the roots of legume plants and bacteria that live on them. The bacteria fix nitrogen from the air into the soil, making it available to plants. The bacteria does this in exchange for starches created by the legume plant. If seeds are to be sown on land that is undergoing Keyline cultivation improvement, it is strongly suggested to use a mix that includes inoculated legume seeds appropriate for the area. Yet another benefit to growing legumes is that they are often high in protein, making them nutritious pasture.
The shape of the land will determine how water flows over it. While some land is flat, most have at least slight valley and ridge shapes. Water will naturally flow from the higher ridges into the valleys, following and eroding the steepest path. These waterlines should be identified at the beginning of a project because they form the framework the land will follow. The placement of buildings, dams, paddocks, and anything else on the farm will be determined in relation to the existing waterlines.
Water flows (source)
All water will flow off of ridges and into valleys perpendicular to contour. When examining a topographical map, water will flow the shortest distance between two contour lines.
Water and Controls
Within the Keyline system, all water sources available to the farm fall into four categories. The first is the rain that directly falls onto the land, the second is runoff from the farm itself, the third is runoff from outside the farm, and the fourth is groundwater. In short, the idea is to capture and hold the water on your land as long as possible by controlling when and where it flows — via channels, keyline plowing, dams, and other features of the Keyline system.
Plowing and the Keyline
The first step in determining your water management plan is to find the keylines of the land. These are on-contour lines that occur where the steeper and flatter parts of the land meet in the center of a valley. A keyline can be found on topographical maps where the contour lines begin to get further apart. This represents the highest contour of the land that can efficiently hold water; there may be lower keylines, but they represent the highest point in a valley formation, not the overall property, where water can be held. Not all valleys have their keylines on the same contour.
The plowing should start at the center of a valley and follow the keyline. As you get further away from the keyline, the contour of the land changes, but the plowing should continue parallel to the initial keyline. This creates a slight grade in the plow cut that channels water in the furrows toward the ridge.
Keyline valley map (source)
Ridge pattern (source)
The furrows’ grade is slight. It is not intended to create any great flow, but to distribute the water more evenly over the ridge and valley formations with a gentle drift. By slowing the flow, the water is allowed ample time to absorb into the soil. This has a side effect of obstructing erosion. If you are familiar with on-contour swales, this concept will be familiar to you.
In flat lands the plowing can continue down the land as needed. In more undulating lands, paddocks may need to be created and plowed from multiple keylines. Keyline plowing can continue up the steeper land as high as the tractor can go.
After the keylines have been identified, a determination of which valleys should have dams constructed in them can be made. It is always worth holding water at the highest point possible to take advantage of gravity doing the work of irrigating the land below the dam. With 15 meters of height, gravity irrigation from a dam will have as much pressure as a spray irrigation system and can be used as such. This would give the farmer the benefits of spray irrigation while letting gravity pick up any energy costs. The cost of building any dam comes down to a ratio of earth moved to water stored. When determining the ideal minimum shape of a dam, the length of the wall across a valley should be less than or equal to the distance water will back-flood. The ideal depth is between 3 and 6 meters. This depth should include 0.9 meters of free-board, the height between the full water line and the top of the wall, above the spillway level. This compensation will allow for 0.6 meters of free-board during rain events where 0.3 meters depth of water evacuates the dam via the spillway. This extra safety precaution is to compensate for large, 50 or 100 year, floods.
Keyline and dams (source)
Types of Dams
High contour dams are installed above the valley keyline. Water from runoff is limited above these dams given their high positioning in the landscape. To fill these dams, swales can be constructed around the ridge to channel rainfall to these types of dams. These steep land dams come at a high price since great deals of earth need to be moved to store relatively little water in these narrow dams. Their water will be freely available for use in pressurized and flood irrigation just about anywhere on the property.
Following the land lower, valley keyline dams are the most common dams found in the Keyline system. Found in undulating lands, keyline dams are more economical than high contour dams; they store greater sums of water for little earth moved. Keyline dams offer another chance to use the stored energy of water to irrigate, but the irrigation area is restricted to the lands below the dam.
In flatter lands dams become even more economical, storing great sums of water for very little earth moved. As the land becomes flatter the wall of the dam will not necessarily find enough height between 2 shallow ridges. In this case the wall is extended back to create sides, or wings, that hold the water in. An extreme example of a flat lands dam is the broken ring dam. The side walls on the broken ring dam extend and curve back on the dam itself.
Finally, in dead flat lands ring dams can be utilized. Ring dams will have no runoff entering them naturally. To keep a ring dam filled, water must either be pumped or piped in from another source. The advantage a ring dam has over a pond is that the ring dam sits above ground level and therefor contains energy, albeit slight, that can push the water into an irrigation channel.
Dams can be fitted with lock-pipes under the wall. While these lock-pipes add greatly to the cost of constructing the dam, they then provide gravity fed water at the turn of a valve. The cost of the lock-pipe will be overshadowed in the savings over running a pump for irrigation. Irrigation can be spray if the total height of the water is 15 meters or more, but even in flatter lands gravity will still allow for, what Yeomans calls, flood-flow irrigation.
Flood-flow irrigation uses an irrigation ditch to channel the water from a dam’s delivery point source, the lock-pipe. Watergates along the irrigation channel can be opened and closed by one man to irrigate several hectares per hour of the land below. This land can be separated into smaller paddocks by fencing that is run on an irrigation steering bank. The bank will allow for more control of water disbursement.
Each paddock should be Keyline cultivated to spread the irrigation, or rainfall, evenly over the land. The keylines should ultimately lead the water to the next lower dam on the property. The slow speed of the water traveling through the keyline system, coupled with good drainage in each paddock leading to the next dam, will allow for sufficient absorption while also preventing the land from ever being over-saturated. This keeps in-line with holding the water on the land as long as possible, using and reusing it as often as possible.
The irrigation channels should be grassed over quickly in dry, windy areas to prevent erosion. This should be a simple task given the nature of the channels to be watered with every rainfall or irrigating.
Swales, which appear similar to irrigation channels, can be used to connect dams, hold water in places dams are not viable, and to help direct rainfall to different parts of the land. By connecting dams of the same level with a swale, you gain additional flood insurance; after one dam fills, the excess water can back-fill the swale and equalize all the dams in a lateral chain before any water is lost over the spillway.
Swales are built on contour so that there is no directional flow. The energy of the rising water will evenly spread water along the length of the swale. The water held in a swale after a rain event absorbs into the soil, adding to the subsurface hydrological flows. This underground water will flow through and down the land very slowly. This water moves so slowly it is effectively held in the land itself instead of on the surface in a dam. If rains are regular, the land should build to maximum water content within a few years; at this point springs may appear in the lower portions of the property.
While swales are not a major component of the Keyline system, they are worth mentioning because modern permaculture uses of swales have evolved alongside the techniques described in Yeoman’s books – and compliment each other well. Swales can be effectively deployed on properties not large enough to support full sized dams. They are also extremely cost effective soft earthworks, requiring no compaction.
When dams become over full there needs to be a overflow mechanism in place that will not allow water to flow over the wall of the dam, but also not concentrate the water such that erosion occurs. Spillways accomplish this task by controlling the overflow of water through a wide level gap in the wall. The water flows evenly and slowly over the spillway and onto land outside of the wall that is also graded nearly flat. From here the water will be treated as rain that falls outside of the dam and its watershed. In a large rain event lock-pipes can be opened as extra insurance against an overflowing dam, but this should only be necessary in extraordinary rains.
Trees plan an important role in the Keyline system. Belts of timber can be planted above keylines on the steeper less suitable slopes. These belts provide wind breaks, erosion control, shelter for grazing animals, and an opportunity to harvest poles for fencing. Trees can also be used along fence and farm roads to like effect. When planted above keylines, the trees provide a plowing guideline that can be followed each subsequent year.
After implementation, the Keyline system offers up a number of benefits. Some of these benefits are seen immediately, such as the stopping of erosion, while others take longer to show and are not as overt, such as restoring subsurface hydrological flows. Still another boon offered by the Keyline system, particularly the system of dams, is the abatement of both floods and droughts.
Often times water is sheeted off the land as fast as possible, increasing stream and river flows greatly but temporarily, before the water finds itself disbursed into the ocean. This fast moving water contains a great deal of energy that is not only wasted, but actively erodes the land on its journey to the ocean. By slowing the advance of water over the land with the Keyline system, the water has a chance to absorb fully into the land.
This restores aquifers and ancient subsurface flows. These aquifers and subsurface flows act as a battery. Once recharged the surrounding landscape will come alive as springs begin to dot a once dry landscape. Further this battery of water will regulate the flow of rivers, preventing large floods by slowing the water and compensating for the flow lessening ill effects of drought.
Additionally water that takes a leisurely subsurface course will have time to be naturally filtered. The results of this would be rivers carrying less sediment. This sediment is not noticeable when deposited in the ocean, but many bodies of water such as the Newcastle Harbour in Australia and the Chesapeake in the United States have been polluted by runoff from improper water management. The implementation of the Keyline system would have a side effect of clearing such bodies of water over the subsequent decades.
The Keyline system provides a total solution to farmers that provides ample water infiltration in even arid regions for cropping or grazing land. This water, coupled with Keyline cultivation, activates decomposition where the top and subsoils meet. This decomposition leads to deeper, richer, more biologically active soil which in turn leads to more productive land.
By capturing and controlling water as it falls and flows over the land, erosion is completely mitigated. The water control system also tempers the bust and boom flood and drought cycles. Ultimately Keyline planning is the only long term, cost effective, restorative land management system available that can be applied to conventional farm and pasture lands without the need for less conventional modifications seen in more modern permaculture solutions.
Ken Yeomans is continuing his father’s work, selling copies of the books listed below as well as offering keyline consulting.
- The Keyline Plan
- The Challenge of Landscape
- The City Forest
Keyline Farming at Nevallan in 1955
This is perhaps one of the oldest known films on the Keyline concept filmed on PA Yeomans’ former farm ‘Nevallan’ circa 1955. It’s somewhat remarkable from a few perspectives:
It was produced by a Bank
It was made at a time when fertiliser technology in agriculture was promising subsidised fertility out of a bag as opposed to conscious design and management of the natural elements
It is 55 years on and we still have landscapes that rapidly shed water, soils that are eroding, rural communities shrinking, cities not feeding and watering themselves, etc. etc. etc.