I've purchased a property with a nice gully that feeds a seasonal stream and is very wet especially in the spring, but the soil is almost all clay. I'd like to build some swales and ponds to begin to control that water and channel it, and was wondering how I should go about building the soil health. Currently there's hard scrabble on the land, huge shrubs, a few trees here and there, wild grasses. It was once, maybe 30 years ago, a sheep/cow pasture, most likely, and lost its soil, in addition to the erosion caused by being on the gully.
Should I just go about building the swales and ponds, and then immediatly seed it with ground cover like comfrey and clover, but wait until later to plant trees, like apple and hazzlenut? What about all that potential useful organic material (the wild grasses and shrubs)? Just dig them under when i build the swales?
D Tyler Huff
Mossy Stone Farms
Catskills, New York State
Location: San Diego County, CA (9a) ~15-18"precip/yr
posted 4 years ago
I have clay soil on some of my property and have been working to increase fertility and water infiltration. I think one of the most important factors with clay soil is getting organic material into it. Not sure if you have done a test to check the amount of organic material in your soil but if it is low I would look to that as a focus for soil building. I think a healthy layer of mulch will start to build your topsoil and allow you to plant the cover species as it breaks down. This will really reduce erosion in most cases. If you have close to zero organic material currently present it might be beneficial to till in some of the organic material, but of course tilling should only be performed if absolutely necessary to kick start biological processes.
Another focus should be building beneficial bacteria and fungi. All your organic material should be inoculated with beneficial bacteria and fungi. They are the creatures that will really allow your clay soil to move nutrients and water around to benefit plants.
For awhile I thought gypsum was the way to go to increase permeability of clay soils but after taking classes with Elaine Ingham I realize the gypsum is a waste because it gets used up quickly and does not create healthy soil biology to set you up for a regenerative system. She has some incredibly great resources on building soil biology.
As for the ponds and swales, that is such a loaded question because it all depends on your environment, so many variables. I would highly recommend Brad Lancaster's books on rainwater harvesting to figure out if earthworks are necessary. If you give some more details about your land, such as location, rainfall, surface runoff levels, topography I think it would help people give you better informed advise on here.
I am big into starting small scale experiments with the types of projects you are trying to implement. Because there are so many variables and the common answer in permaculture is "it depends," I just start my projects very small to see if they work. Then if they don't work you have not wasted much time/effort and you can easily make a change to some variable to see if that gets you going in desired direction.
remediation of a gulley is a little more complicated than just building berms (swales are scooped out areas, berms are like mini dams).
In this situation you will most likely need to run series of berms across the gulley to slow the water down and let it deposit the heavier materials the water is carrying.
In the end, you should end up with some nice terraces. up at the gulley head, a swale dug in front of the gulley, followed by a berm created from the dirt removed to dig the swale would be a good way to start the project.
Doing this will let you see just how fast the water moves, a gulley is usually a good indication of fairly fast water movement.
The more berms the more the water will slow down before flowing over the top, if you get overflowing, you will need to do some kind of cover for the berm or else it will fail and you will be back at square one.
If you could put up a picture, it will help in being able to give direction on the best methods to consider.
If you can, I would enlarge and deepen that pond, that will give you a nice emergency water supply, or at least a water supply for gardens.
Swales with berms will work well on that parcel.
Make the swale about 1 to 3 ft. deep and at least 3 ft. wide, on contour.
Take the dirt and use it to make the berm about one foot behind the downslope edge of the swale, set these about every 20-30 feet from highest point to the end of your parcel.
Using multiple swale/berm sets will help control the water flow and give you lots of plume. You can then think about putting orchard trees or gardens between, depending on how well you slow the flow down hill.
Be sure to make a way for the water to flow from one swale to the next at alternating ends, this will allow excess water to not wash out your berms and make it zig-zag down the slope.
doing this will help with the ability to make the area useful for trees, bushes and or garden areas.
If you can do the pond work, that will give you a place to direct the overflowing water before it continues to the stream where it ends up now.
From the photos, you might want to go the length of the gulley and widen the pond some, that way you could possibly even use if for fish raising.
Planting some N fixer ground covers will help tremendously. Since the photos show no soggy ground, you probably don't need willows to suck up excess water.