Rapidly-Cut Swales with Tractor Blade

3 Miles of Swales Cut in 5-Hours

We are making early progress on our 320-acre Missouri permaculture-farm project (Jordan Rubin’s Heal the Planet Farm).  Last fall, a local dozer operator was brought in to dig the first swales.  It was a small dozer but it did a respectable job and did the work in a relatively short period of time compared to an excavator. See the blog post with video here.

Before we brought the dozer back in this spring, Kevin, a long-time farmer in the area who is also Jordan’s lead farmer on this project, suggested that we simply try the 135hp farm tractor with it’s 9-foot tilting scraper blade (it’s just over 6′ wide when fully angled at 45 degrees) to see what kind of swales it would cut. It certainly seemed worth trying though I’d never seen it done before.

Adam and I headed out early one morning with the laser level and marked off about a mile of swales with white-wire flags.  When Kevin arrived later in the morning with the tractor all he had to do was adjust the angle of the blade, drop it down, and start running.  He ran three passes on every swale we had marked and did it all in about 60 minutes!

We repeated this process over the next two days and in the end Kevin had cut about 3 miles of swales in about 5 hours including the time it took to put in the spillways.

This is huge… for with just a basic farm tractor and a simple blade the farm is now capable to holding an additional 100,000 gallons of water every time there is a good rain and the swales fill.  And with all of the rain they have had this spring it probably comes to 1/2 million gallons of water that has now soaked into the landscape rather than running off into the ravines and creeks.

Is this really helpful?  Because of the poor quality of the farm’s soils (low organic matter, compaction, clay) it’s ability to absorb water is very limited. The recent soil percolation tests we did showed that the soil can only absorb 1/3 – 1/2 inch of rainfall per hour.  When 2 inches of rain pours down within a one-hour period (not uncommon here) that means that most of it runs off the property adding to flooding conditions down stream and leaving plants thirsty just a few days later.  What if the farm had absorb all 2 inches!  No flooding downstream.  More water for plants. Better plant growth.  Greater yields. It’s all very simple math really.

contour flags

With the first cut, the blade cut in an average of 6-8 inches, scraping the disturbed soil to the downhill side

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Second Pass at Swale

With a second and third pass the wheels of the tractor dropped into the swale cut which dropped the blade down further as well, allowing the blade to take another 3-4 inches from the bottom of the swale with each additional pass.

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Swale with water

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Berm removal to make spillways

By pulling away the berm soon after being cut, the sod below is not damaged and now becomes an excellent spillway capable of handling a lot of water without eroding.

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Swale 3 months later

Here is what the swales look like 4 months later.

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4 Misssouri Swales

Field view of 4 of the freshly cut swales. An existing livestock pond on the right.

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Swale Map for North 60

Hear is a top-down view of  the locations of the same 4 swales. All 7 of these swales cover about a 40-acre area that is 1/3 of a mile long. The white marks along the swale are where we placed the spillways.

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Missouri Swales as they are installed

Here is a view of the entire 320 acres with the location of the swales and existing and proposed pond locations. This is just the beginning. The plan is to put in many more swales, ponds and also keyline the entire farm.

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Perc Test

How do we know that the soil only absorbs 1/3 – 1/2 of an inch of rainwater per hour? We did multiple ‘perc’ (percolation) tests throughout the farm.

Soil Perc Test Marker

How to perform a Perc Test?  Dig a 1-foot wide/deep hole. Fill it with water and let hole saturate for several hours. 
Return and drive in a stake with 1″ markings. Fill the hole again with water close to the top to any of the lines. 

Return in an hour and note how much the water level dropped. If it dropped 3.5 inches then this is your percolation rate… 3.5″ per hour. 
This means that your soils will be able to absorb about 3.5 inches of rainwater each hour. 
A good percolation rate is about 4-8 inches per hour. 
Less than this and water could be running off in a hard rain.
More than this (usually in sandy soils) and there could be a significant loss is soluble nutrients and the inability of the soil to hold water for dryer times.

The best solution for slow or fast percolation rates is to build soil organic matter and soil life. The life in the soil needs the organic matter for food and shelter and as they process this organic matter they turn it into humates that act like gluey sponges that can hold water and nutrients.

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Bill with Laser Level

Me (Bill Wilson) with laser level — With two stadias (long measuring rods) and laser readers, Adam and I were able to mark out the swales quickly. One of us would take the first readings, putting in wire flags, and the other would come through and double check the first’s readings. Just like in carpentry “measure twice – cut once”.

Adam - Swale is 20 inches deep at this point

Adam Haugeberg, the farms full-time permaculture designer and worker, measures the depth of the deepest swales. The swales varied in depth of between 14-20 inches. Where the soil was softer, the blade dug in deeper. With this kind of blade there is not a way to pre-set the depth so the operator’s skill and ability is important.

I know this is not a common way to cut swales and the water sits towards the back of the cut instead of soaking into the berm, but for the amount of time it takes to put them in and for the amount of water the swales hold, it certainly seems like it might be a perfect option for many other permaculture design projects.  It’s perfect for us because the swales also create the contour template from which our keyline plowing plan will work from.  More on that later.

Give us a shout if you have questions.

If you have already experimented with a tractor blade or you end up trying what we’ve done, please share with us what sort of results you get. The more we learn from each other…the better.

Toward a greener world… Bill

P.S. Cody asked a great question in the comments below about mowing.  If one does not have livestock to keep the vegetation down, and this is important to do, here is a sketch of how to approach maintenance. Remember, the scraper blade that cut the swales is 9′ wide but when turned as fully as possible (45 degrees)  it cuts a swath just over 6′ wide, perfect for a 6′ wide brushmower.

Mowing in Flat Swales cut with Blade

 

15 thoughts on “Rapidly-Cut Swales with Tractor Blade”

  1. Excellent post, video and comments.
    I have watched this several times over the years but it was never too relevant to my rocky limestone hills in Texas. Now, I have the opportunity to install swales on properties in Georgia and South Carolona that actually have soil, and they each have a small tractor and a blade, so I will be trying this over the summer 2017. Is it beneficial to mow the grass short before running the blade?? Do you have any more recent suggestions or observations?? Thanks, Bryan H.

    1. If you can mow it does help to have shorter vegetation so that everything rolls over nicely. Be sure to have your cover crop seed handy and some straw mulch to hold the seed in place for the first rains. I recommend irrigating the cover crop until it is established if this is a relatively easy option to accomplish.
      Also… the dryer the soil is the more difficult it typically is to pull a blade through. Some moisture in the ground makes for smoother cutting.
      Good luck Bryan

  2. Bill, Awesome post! It is good to see others using tools that are commonly available on farms to do this work. I am also planning on using a tractor for much of of my swale, and subsoiling work on our property in MO also. I found a video last year of a gentleman using an old Ford 8n and a 2 bottom plow to make swales that turned out pretty good also. Just make multiple passes and adjust the attachment and they turned out pretty good. I think with a few select attachments to our tractors and you can do some amazing things!

    In the case of the blade you used, a pass with a box blade with the shanks fully down would have broken it up so that you could go deeper and work the contour of the swale. Maybe something to consider as you continue to work your projects. Awesome property you have there and it looks really exciting. I can hardly wait to see it develop! I am going out to our place in Oct to use the laser level and mark the location for our first swale and will have it done the first week in Nov just in time to put my fall trees into that swale. For our first swale I am having a local guy with a land mover do the work as i don’t have the attachments for my tractor yet, but hoping the next 3 or 4 swales after this one will all be done with my tractor and a few attachments.

    I am looking forward to seeing how your projects go!

    1. Hi Mike. Don’t know how I missed this but with Greg’s recent post here it brought me back in for a quick check.

      Everything depends upon the size of the equipment. A large dozer will do a quicker job than a small tractor pulling a blade. For us, it took three passes for both pieces of equipment, but the tractor could run about 3 times faster…so…1/3 the amount of time with the blade vs. the dozer.

      The excavator is the same deal. It is a good sized and have a competent operator they can do a lot of work and do it more accurately.

      So… if I had a large piece of property and wanted to make a lot of relatively small swales (4’wide, 1.5’deep) I would use a blade on a large tractor. If I wanted to craft some large and well shaped swales I would use an excavator.

      The last question we ask…what piece of equipment do I have access to? Often times, working with what we already have and just getting to it is the way to go.

  3. Good post. I was surprised how easily that blade cut through without any ripper teeth. I have some comments and questions about the logistics of keeping the grass/brush managed around these swales. I did the same thing making swales here in missouri using a double bottom plow. These things do hold water well but ive found that presents a new set of problems. Mainly that everything around the swale is to wet to get in there with a brush hog to keep the land managed, the tractor just sinks right in and my berm was to small to ride on top it and mow down it very effectively if that makes sense. It wasnt until about mid summer that i could get in there and cut the grass that exploded in that area from all the water sitting there. Part of the problem could have been from the extremely wet year we have had. I love keeping the water but its been a real pain to manage so far. Im not looking to do the food forest thing, just rows of trees for a silvopasture setup. After dealing with this im thinking of reworking things to get a bigger less steep berm that the tractor can ride on with the brush hog and space my trees at the bottom of the berm so there is room for the tractor on top to cut. I was wondering if you guys had had to deal with this issue yet or have some system that works. Maybe the best thing will be to let the livestock keep it managed but im not there yet. What do you think?

    1. Hi Cody. Finally had the time to make a quick illustration on how we are approaching the mowing on this project. This is one of the advantages of using a blade rather than a double-bottom plow to make the swales–the swale-cut and berm are flat so it’s relatively easy to get a blade in there. Good Let us know what you work out to make your maintenance easier.

  4. We are going to do this on one small pasture. I’ve already started raised beds with the stick method and have planted fruit trees. Guilds are next and a rabbit garden to feed our meat animals. We raise all our livestock naturally and this fits in perfectly! Thank you very much for the detailed instructions.

  5. Great article! I’m curious how the bottom of the swales came out- that is, the bottom of the swale should be level across its length, and if there was varying depth, it seems that you’d get pockets that are wet and some dry as a result of the varying depths. It’s probably not that important on a broad-acre project like this and is certainly a great step toward making large-acreage swales economically feasible. I guess the key is for water to not move downhill once it’s in the swale, and so the varying depth probably isn’t important. I’d be interested to hear your thoughts. Kudos on a great project!

    1. You’re spot-on Greg. You answered the question for yourself. Yes, the goal is usually to get the bottom of the swales perfectly level so water is held evenly across the entire landscape, but this is not always the case. Sometimes we will design the swale to be deeper at various points along the length if we have certain plantings that can use or prefer more water. But in this case, there will be so many swales we are primarily interested in just holding as much water as we can considering how quickly we are able to put the swales in.
      And like I said in the post, with the contours clearly marked by the swales we have the system set up for the keyline plowing that will follow. And the amount of water the keyline cuts will hold just might dwarf the holding capacity of the swales anyway…at least after each pass.
      Thanks for the comment…

  6. I’d do this in a minute if I had more than a suburban backyard (although it does boast a raingarden) CONGRATULATIONS on superb stewardship. It also looked as if there might be some milkweed growing on one of the swale banks & the Monarchs will thank you too!

    1. Hi Shirley. Thanks for the comment. This is going to be an amazing project to follow over the next 10 years. And we’ll be sure to have plenty of milkweed for our friends.

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