Keyline is a farm water management system designed by PA Yeomans in Australia. Water is a precious resource, in Kent we can go weeks, months and occasionally whole seasons without rainfall and hose pipe bans are not uncommon.
In 2013 we had a long cold winter with limited rainfall followed by a long dry summer and as I write we are experiencing weeks of constant rain, the level of our top lake has gone up by over 12 inches in the past month.
A very conservative estimate of the past months rainfall here at Landew’s is 6 inches , across our 30 acre site that makes 814,620 gallons of rain water that has landed. Most of that has just run off the site but by constructing swales, dams and using Yeoman’s keyline ploughing technique we plan in the future to be able to store and use some of this one million gallons of rainfall instead of letting it run off.
This will bring two significant benefits to our farm, it will reduce soil erosion from water run-off and we will have water available for irrigating our pastures in the summer months providing better and more consistent forage for our animals.
A swale slows run-off water as it travels down a slope and allows more to permeate in to the soil. The excavation is made along a contour line with the soil being deposited on the down hill side of the excavation. This is then planted up with trees or deep routed plants. We also plan to construct some swales that will hold water in them (either with a lining or using puddled clay) so that we have water for irrigation.
The images show a keyline plough being used and a cross section of what the plough does under the surface. The plough is not used to turn the soil over, but it opens up the soil allowing air and plant roots to penetrate deeper in to compacted soil. As can be seen in the second diagram this brings dramatic improvements to the growth of the sward which then opens up the soil further and improves drainage. The plough is also used to improve water retention on the land by either ploughing along a contour line, or slightly off contour when going on to a ridge to drain water up a ridge not down in to a valley.