I looked at a homestead property that has a 20 acre tiled hayfield. What affect does tiling have on trying to develop land with permaculture methods?
I'm an agricultural engineer and am currently doing some research simulating the effect that subsurface tile drainage has on the loss/transport of water (and nutrients). You're property is likely in the Upper Midwest, and was tiled to allow row crop production (i.e., corn and soybeans). Somewhat counter-intuitively, most of the water "exported" from the soil by tile drains actually enters the tiles from below due to a rising groundwater table. Yes, the tiles intercept some water as it infiltrates the soil column, but the vast majority of the water flowing through tiles (on an annual basis) is from groundwater fluctuations. If the property you're looking at has significant pothole depressions with surface intakes, then this would add to the amount of water that enters tiles from above.
The ramifications of having tiles on your land could be both positive and negative, depending on your desired uses of the land. Also, tile drainage systems have several components, and if I were you, I'd want to know more about the system. Here are some questions you should obtain answers to:
1. Are there any pothole depressions in the landscape (i.e., very shallow pond/wetland/marsh areas) that are usually dry, but can hold water seasonally or for short periods during wet weather periods? If present, do they have surface intakes?
2. Are there any drainage district tile mains that run through this property. Tile "mains" are somewhat publicly owned and were installed by drainage districts to convey water from sevearal adjacent tile "laterals." Tile "mains" eventually enter a drainage ditch, stream, or river. This is important, because if you wanted to, you could fairly cheaply "plug" your drainage system if you know the location where your laterals enter the "main." You could just excavate at the downstream end of the tile and block your lateral from entering the main. However, it would be unlawful to alter or impact the function of the tile main in any way, because you'd be affecting other peoples' drainage.
3. Personally, I would not shy away from land with tile drainage, especially if I could obtain more information about the system. If you have potholes, you could do some pretty interesting things with them related to unconventional crops, water "recycling", etc., etc. They are also great habitat if the hydrology is restored (i.e., block or slow the drainage). You could even "manage" the drainage by building a control structure that allows you to manage the water table levels.
Maybe the biggest thing to think about is that tile drainage indicates intensive agriculture has occured on this land. The soil has been worked hard, and tile drains are a known pathway for nutrient loss. But lots of new tiles have been put in recently, so it's also possible (but unlikely) that this land hasn't been farmed that long. But if this property meets your needs otherwise, I think you can work with this. No, it's not a great and sustainable practice in the big picture, but if you learn more about the system you could actually (potentially) make it work for good.
I'd be happy to answer more questions about this. I'll follow this thread, or you can PM me. If you happen to be in Iowa, I could probably help you track down some more info.