Keyline Design
Keyline design has been around for a long time and has many different elements. Over the last decade, I have seen a significant shift to implement these principals on farms across the United States. In the past, vast fields were leveled for speed, ease and water drainage causing significant damage to the environment.
Reasons for flat fields
The reasons are simple, tractors pulling huge equipment can drive in any direction to plant, plow, spread amendments and harvest. While this increases speed for the farmer, it can also affect production per acre due to less water. As the soil dries out, the surface tension goes up and water must overcome this resistance to absorb into the ground. This means that as the soil continually dries, the surface hardens, and the rainwater runs off to ditches, streams and ponds. This further compounds the issue because water is not absorbing into the ground like it should be. It washes away our topsoil’s, fertilizers, seed, and amendments while contaminating our waterways, estuaries streams and oceans.
You can have your topography and farm it too!
Huge sums of money were spent on moving earth to facilitate flat fields 4 decades ago. I am happy to say that huge sums of money are once again being spent across the country to add topography back to the farm landscape. Small mounds, no more than 2 foot high, are following the natural contour of the land. While this is not conventional keyline design ditches, farmers have found the balance between water retention and production. Modern tractors and equipment can easily transverse the 2-foot-high humps. The humps are not meant to stop the water perinatally like ditches and ponds. They are meant to slow it down enough, so it has a chance to absorb into the ground. Depending on the farm’s crops, rainfall and needs, the farmers can choose to increase or decrease the mounds height or distance to the next mound. This flexibility gives the farmer ultimate control depending on the desired crops and farm characteristics. In a hurricane prone area, the farmer would want less of a mound than a dessert. A steep hill would want more of a mound than in the flat plains.
Should you start at the highest elevation or lowest first?
Typically, I would recommend starting at the lowest topography and working your way to the highest parts. While there are many reasons to do it the other way, my recommendation is based on production. If you decide to start mounding the highest topography and plant the lowest part, any runoff could affect the crops below. I recommend planting the highest topography with crops and working on the lower topography. Over the winter months when there are no crops are planted, you can move to the upper areas. This limits how much disturbance there is to your contracts and lets you learn how much mounding will be needed. As I stated earlier, the flatter areas need less mounding than the steeper slopes. You will start to notice the effects on the lower sections first because any water absorbed into the ground is affected by gravity. The water table will start to raise in the lower sections first and then you will start to see the effects on the slopes after the water table has reached saturation.
Should I install large mounds?
While I know it is tempting to go for the gusto and want to maximize effect, think about the long term goal first. If you are installing a permaculture orchard, YES! If you are planting soy and corn, ABSOLUTELY not. Corn and soy cannot take huge amounts of water and don’t like soggy feet. They will deal with quite a bit of moisture but know your crops. If you row crop, consider if your equipment can traverse over the mound or if you must travel within the rows. My preference is to be able to plant and harvest in any direction however, depending on your topography, this might not be possible.
Should I mound or ditch?
Simply put, permaculture you ditch, cash crop you mound or back angle.
In my permaculture orchard, I dug a 2-foot-deep ditch and mounded it on the downhill side. Any rain running down the hill will be trapped in the ditch, the mound acts as a damn to give me another foot in height. Also consider overflow pipes. In a heavy rain, you don’t want water to breach the damn and erode the mound. My reason for ditching on the permaculture orchard is “Chop and Drop”. Unless there is disease or infestation, any pruning, weed pulling or dead fruit are put into the ditch to decompose. I also add woodchips to the ditch, they don’t take up much space and decompose to natural fertilizer. Adding wood chips also helps reduce Mosquitos since the water is amongst the woodchips. Every few years, I have to dig out the ditches, but the compost is put on the uphill side keeping the nutrients close by. The ditch is then filled in with fresh wood chips and the process starts all over.
On the flatter areas with cash crops, mounding is recommended. If you ditch, a tractor wheel or implement could get stuck. With mounds, the worst case is that your equipment ruins part of the mound, not the other way. There are several techniques that can be uses. I have already talked about the mounding and ditching but you can also terrace your property back into itself. Traditional terracing uses excavators or manual labor to remove huge sums of dirt, I am nor talking about this. You can use a bulldozer to make small steps on the land with each step slanted into the hill. As the rain runs down the hill, it will settle at the back of the step before completely filling and continuing to the next level down.
How can I improve water absorption?
After you install the keyline design mounds, stairs or ditches, let the fields compact for several years. Once the land has stabilized and you have fixed any erosion issues, you can go back in with the chisel plow. You don’t want a bottom plow or anything to agitate the water retaining structures you just installed. Take a deep chisel plow and go as deep as you can without destroying the topsoil’s by spinning tires. This might take several passes or even years to accomplish. Go parallel to the water retaining structures as if you were adding additional ditches to the land. The goal is to go as deep as possible and loosen up those deep minerals.
Applying Amendments
A great time to apply amendments is just before or after a deep chisel plowing. This allows the amendments to get deeper into the earth for longer term retention and even distribution. Mouldboard plowing is commonly used for similar applications however, I do not like this method. Mouldboard plowing injects a liquid solution at a set depth while chisel plowing the land. The issue with mouldboard plowing is that you can get a cake effect with your amendments. At the 18 to 24 inch level, there is an abundant application followed by a section of un-amended soil in the middle and a 4 inch layer on top that absorbs topically applied amendments. Any planting you choose that has a root depth between 5 and 18 inches will be in the unaffected zone. The amendments will eventually leech out to the surrounding area, but this can take years. If the roots get down to the 18-to-24-inch depth, they can be easily burned by excess fertilizer, lime and a combination of amendments. I prefer to make my applications and chisel plowing just before a rain so amendments can seep into these trenches and distribute more evenly.