Does he have a map of the tiles? Does he know how deep they are?
Most tiles here are put deep enough to never get hit by deep tillage equipment even after "acceptable losses in topsoil", which means at least 2 feet down and usually 3-4. Definitely deep enough to do Mark Shepard style 2 bottom plow swales.
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Location: Poplar Hill, Ontario (near London) - Zone 6a
posted 3 years ago
In my area a lot of fields have drainage pipes, and more is going in all the time. In a workshop with Mark Shepard he did say you can block the outflow by finding the pipe(s) that drain the water, and putting up a simple wooden block that holds in the water. If you need to drain, you just take the block out.
Rather than whether the drain and the keyline swales would complement each other. Keylining prevents erosion of surface soil, and moves water from wetter to drier areas, retaining as much as possible in the soil, while the drains will be trying to drain the field as fast as possible, especially in the spring. Pretty much opposite tactics for opposite intended outcomes (either giving plants and soil extra water, or allowing for machine tillage earlier in the season).
I would say if the resources are there to do the keyline plowing - do it, it certainly can't hurt, especially the lighter subsoiler stuff, or small swales. And if they want to keep water on the site as long as possible, consider a pretty permanent valve on the output drain. (And of course, do some testing to make sure the equipment won't hit the drainage pipe.)
It's more site specific too. I'm working on a fairly flat flood plain now, and while we strongly considered keylining, we opted in the end to just plant the trees on contour, and plant trees that were adapted to having 'wet feet', knowing that you can't really change a flood plain into a not flood plain - at least, if you did, it wouldn't exactly be working with the landscape! We'll monitor the site over the years, and if resources become available, we may keyline plow it, but the trees will be planted to accommodate that.
Location: Central Texas zone 8a, 800 chill hours 28 blessed inches of rain
posted 3 years ago
Drain tile is what is being described. It is plastic pipe normally 4 or 6 inches in diameter, most often perferated to allow water to seep in from the soil and be channeled off below ground through the pipe.
I believe this is when they bury drainage "tiles" which are drainage pipes, under the field to encourage water in the subsoil to move laterally. Wikipedia has an article about it. The original implements were made of clay, which I think is why they are called tiles. Modern drainage tiles are made of plastic most often.
Seems to me that if you found the end of the drain tile and capped it or put a valve on it, then you would not be loosing that water, and you could bring in a subsoiler or what-have-you and do the keyline work.
As others have pointed out drain-tile is laid fairly deep to avoid interfering with plowing, etc. So I doubt it would be an issue. Plus if you have a tractor powerful enough to drag a sub soiler you would probably just cut right through the drain tile!
The other option is to dig out the drain tile completely, and then go about your business.
Location: Grand Valley of Colorado's Western Slope
posted 3 years ago
And, if you cut through the drain tile and render it useless, then you won't be channeling water off.
I use that perforated pipe to distribute water. I don't want ditches everywhere, but I do need to carry the water from one place to another, and I thought if I put in the perforated pipe I would be giving the soil some water. I always wondered what its formal purpose was.
I'll just add, the general principles have already been described, but there's still a whole lot of specifics that need to be addressed--how big is the field, what is the slope, features? people have talked about "keyline plowing" is there a ridge and valley to orient to?
If this is more or less a lowland/wetland, flatland, then you might even start thinking about chanampas and getting real creative with ponds or the like, and as has been mentioned, tiles can be cut through, dug up , or plugged, as it serves your design.
Remember that as your soil organic matter increases the soil will hold much more water meaning less water will make it to the tile drain system. In time the less and less water will be lost to the drain. Seems like a key line system will prevent some of the water otherwise lost to the tile drain by intercepting and spreading it more over the field.
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