By Soil Health Champion Craig Conley
Creating drought adapted landscapes requires slowing, spreading and soaking every drop of water possible. The healthy soil project at the C-B Ranch is applying keyline principles and tools to make maximum use of precipitation on a degraded 10-acre pasture. By maximizing water infiltration and storage, we hope to restore both soil health and improve wildlife habitat conditions and apply what we have learned on a larger scale in the future. A key part of this strategy is improve the capacity of the land to capture the more intense rainfall events that are becoming a larger portion of our total annual rainfall. Our ultimate goal is to manage the landscape for long-term drought resilience (survive long dry periods and take maximum advantage of water when it comes).
The 10-acre pasture has roughly a 3% slope and collects some water from adjacent hillsides. The entire field was plowed and planted in a monoculture of crested wheat grass over 40 years ago. Over the years, sagebrush as become the dominant plant with the crested wheat grass becoming less abundant in spite of periodic brush hogging. Over half of the pasture is now dominated by purslane (the red color areas), sagebrush and kochia (in the cool season). This year we had excellent native grass production on the south side of the pasture as a result of a strong monsoon season. In recent “normal” years, the pasture is largely bare ground in the early spring and by the end of summer. As one can see from the photo below, a significant amount of water runs off the pasture and down the arroyo that is located along the bottom of the pasture.
As shown in the photo, the project combines shallow swales, keyline plowing (just above each swale), seeding and microbial inoculants (Johnson-Su bioreactor compost tea) to kickstart the system.
Keyline: Keyline design is a system of principles and techniques developed in the 1950s in Australia to optimize a landscape’s water resources. The Keyline or Yeoman’s Plow is used in a specific pattern of topographical sub-soiling along the contour of the land. There are a number of excellent online resources for learning more about keyline design and implementation listed at the end of this blog post.
Swale: Mark Shepard in Water for Every Farm (2020) defines a swale as a linear excavation in the ground or a shallow trench. This trench may or may not be accompanied by a berm or “steering bank”. The swale and berm are often combined under the term swale. Swales can be large and become relatively permanent features on the landscape or small (as in our case) and disappear in a few years after they have served their purpose. Swales can be built on contour and used to spread water or they can be built at a slope (off contour) to channel water to a particular location such as a pond.
We started planning the project by collecting terrain data using a consumer DJI drone. This was very new but exciting process for a Luddite like me. A workflow was developed by Lucas Chavez and Chelsea McMullen to collect the necessary topographic data for the site, use that data to create a design and then transfer the design on paper into pin flags on the on the ground.
The contour map gave us a powerful way to visualize the slopes and alternative scenarios for placing the swales and keyline plow rip lines. A pure Keyline design would have had equally spaced parallel treatments tied to a single keyline. This would put swales and rip lines off contour (slightly steeper). We decided staying on contour would be simpler to install and meet our goal to capture and spread water evenly across the landscape. Had the topography been a bit steeper and followed a more pronounced valley ridge shape, we might have done things differently.
The process we used to collect the ortho-photo data using a consumer drone and turn that data into a digital contour map was documented and is available if others would like to try it.
The swales were installed using a single mold board plow, taking two passes for each swale. While these swales are relatively shallow and rough compared to many of the swales installed in permaculture projects, they are relatively easy to install and maintain with basic equipment and skills. Over time, we may want to let these go and install new ones in the intermediate spaces.
Images by Craig Conley
Following swale installation, we ran the two-shank keyline plow at about 15”. The keyline plow setup allowed us to create deep rip lines with minimal surface disturbance while seeding and adding the microbial inoculant in one pass.
Images by Craig Conley
As an experiment, we also seeded the base of the swales by hand. The prolific growth from the swale seeding is promising. Our seed mix is a cover crop that includes clover, forage turnips, vetch, sanfoin, alfalfa, winter wheat, oats and barley. One challenge in seeding is some of the seeds require deep (2”) seeding while others require shallow (.25”) seed depth. We ended up mixing it all together and channeling it into the rip lines. We will likely reseed some areas again in the spring. Once this cover crop has had a chance to add some much needed carbon to the soil, we will follow up with a native perennial grass and shrub mix.
The results so far are encouraging. We have been lucky to get a few rains since planting so we have had lots of growth already. We are not sure what will survive the winter and the deer and elk have already discovered this new growth and are utilizing it. That is not a totally bad thing as this is largely for habitat purposes.
Images by Craig Conley
This is the first step in what is likely to be a multi-year process of building soil from the top down. While we were able to plow 15” deep this year, next pass, which may happen next year or the year after, may allow us to plow 20” deep. Over time, we hope to replicate the process illustrated in the Figure 7.
Room for Improvement
For the most part, the project has gone as planned but there are clearly areas for improvement.
- We will likely add some type of roller or cultipacker behind the keyline plow the next time we seed with it to break up clods, press the ridge down a bit and create better soil seed contact.
- In spite of having had fairly decent rain before plowing – over 2 inches – the soil was pretty dry (early September) at depth which made pulling the plow much harder for a small tractor. Spring plowing may work better.
- The tickle pot seeders were temperamental. A person needed to walk behind the tractor while planting to monitor the flow of seeds as the system periodically plugged up. This will likely be an even bigger issue with native seed mixes.
- We will continue to monitor the performance of the swales. We are not sure how much effort to put into the swales. This minimalist approach may be all that is needed to establish vegetation and increase the infiltration rate of the soil. We figure this process should take around 5 years. We may experiment more with a double mold board and triple passes.
- We are still working out ways to efficiently monitor this. Most monitoring protocols are for areas while this is really about changes in narrow strips. We are exploring ways to use the drone for this.
- Still not exactly sure how the transition from cover crop to more permanent native perennials should be implemented.
A Google search of “keyline design” will produce lots of results both in printed form and videos. Here are a few that we found useful. It is very easy to drop into a rabbit hole with this so be forewarned.
What is Keyline Design? A fairly detailed but accessible written description of keyline principles and applications from British Columbia.
Managing Water on the Landscape Excellent video by Mark Shepard