Swales on drained agricultural land

Hi all,

I have a contract designing a small organic farm on a piece of agricultural land that has been previously modified in the conventional manner of making wide mounds with drainage ditches between them.

I would like to make swales on this land to help provide some diversity in terms of the soil conditions (ie the mounds would enable us to plant fruit trees as wind breaks and for increased diversity on this quite humid piece of land).

Does anyone have experience with this? The drainage ditches previously installed obviously changed the contour lines - should I mark my contour lines on the mounds only and simply use the drainage ditches as my overflows? Or should I fill in the overflows? Or dam them to create small rain gardens here and there?

Any ideas would be welcome!

Thanks,

Kate

This is not a new post, but we'll see if the poster is checking back.

I became interested also in Swales and so cut some with the backhoe and hand shovel. Nothing wonderful but a start. This in in the High Desert. Here is picture to show the result so far. These catchments are 6-5' deep and filled with water that would have run off. I haven't filled the holes with gravel or rocks and planted trees there yet, the areas around the catchment will have to be fenced to prevent the rabbits from eating every thing as it grows, the land is fenced to keep out the wild horses, we love them, but will not stop the rabbits.

Richard

Hi Richard,

Thanks for the input. However, my post was regarding drained agricultural land. Maybe you don't have this practice down where you are, since it seems to be dry enough, but up here in Quebec we have a LOT of water. The standard practice for large agricultural fields is to dig parallel ditches every twenty or thirty feet and install agricultural drains in them to lower the water table, which is a bit of a ridiculous practice. In any case, the result is a field which is basically a series of mounds and ditches. Before knowing what I was looking at, I once envisioned turning them into chinampas, which would be pretty sweet. Now that I know, though, I see this would involve removing the drainage first...

Anyway, any thoughts are welcome!

Kate

Are there drain tiles or pipes under the soil? If so, you might need to have them dug up with a subsoiler. If not, you should be able to install swales over the existing earthworks. Exactly what that pattern might look like would be easier to figure out if you could post a satellite photo of the land.

Greetings Kate, Just came by and saw you thread. The Catchments are in the picutre are/were to stop the water just running off. I haven't made true Swales , filled the catchments with rock or planted trees. This was done in the high desert Nevada.

I understand you have a different thing in mind, what have you done on that so far?

Richard

Hi Kate,
In different regions, drainage tiles can address different problems. It sounds like, it is a question of drainage of excessive precipitation in your region. In arid or highly evaporative lands, tiles serves to reduce a water table but also to avoid the problem of rising salt that occurs in irrigated lands if surface capillarity is ever established! I lived in Colorado on the Front Range in an agriculture area with expansive clay, I learned much more about drainage systems than I had ever planned, and it was expensive in time and treasure! We had a drainage system that covered similar acreage to what you describe. Your problem is likely to be much more tractable.

The best lesson that I learned was to talk to the oldest farmers in the area or, if you can, the person that installed the system to understand how it was designed and what was the purpose of the system. We were at a loss until an elderly women living in the area showed us the location of the common drain for the land well beyond our property. It was not intuitive, since it was on the uphill side but the drainage went deep and deeper into a very deep and hidden ditch. Ultimately, we found some old maps from the local cooperative extension library that explained the system but the help of neighbor was still essential. Hopefully, your situation is more straightforward.

Tiles are common on some excellent conventional ag land in the US and for better or worse had a purpose. In the US, these systems are usually placed well beyond the reach of a sub-soiler to prevent damage, and it was a major operation to dig up sections for replacement. I don’t know the depth of your tiles or the lay of the surrounding land but it is important to understand the consequences of changing the system. If your land has subsoil drainage from surrounding areas or uphill connected drain systems considerable swamp or bog areas could result. Once you know the direction of drainage and the extent, then selective blocking of tile lines allows experimentation. Such systems have also been used to fill catchment ponds that are dug out in the downstream collection point. You may also collect a toxic brew from neighbors. Leaving tiles in place can create different environments, since drainage may allow earlier start to growing season, if the land stays dried out. Water saturation is also another factor that can greatly alter over-wintering of perennials.

The best hope may be to find an experienced older farmer that knows the land. They may not agree with your goals and methods and think they are weird, but if approached correctly and treated with respect, these folks are very smart about the land and how it might respond to changes. (In contrast, our local cooperative extension agent trained at a corporate influenced land grant university was neither useful nor sober in trying sort out these issues.)
Good luck with your project!