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| I'm interested to get some feedback on expanded shale/clay/slate in soil, particularly in a raised bed.
Note that the stuff has many names:
Since expanded shale is used for construction is can be obtained in bulk for excellent prices compared to vermiculite for example. It's also claimed to last much longer since it's quite hard. Specifically: A general purpose soil base for a raised bed vegetable garden that will last. Ideally skipping things that will decompose or break apart quickly, and choosing things more durable ingredients. Base recipe so far, equal parts:
6 cubic yards in total. So far price would be $140 for Arkalite, $60 for peat moss and free compost. I consider this an excellent price considering the quantity. Feedback? Al, I've read the numerous posts you have. I love the detail and science. A large number are container centric, I would love additional input on raised beds. Thanks! |
Here is a link that might be useful: Reed sedge peat
Follow-Up Postings:
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| Soil is composed of minerals (the sand, silt, and clay particles), organic matter (which is decomposed), air, and water. You cannot have a good soil to raise plants without all of them. If your soil is largely clay based organic matter seperates the clay particles so nutrients and moisture can move through the soil better and plant roots can spread out easier. If your soil is sand then the organci matter fills in the spaces between the soil particels and helps hold both nutrients and moisture in the soil so the plants can find them easier. Adding expanded shale simply adds more of the mineral component to your soil which might, in clay, seperate those mineral particles some if they are bigger in the same way sand would. In sandy soils that shale will do little to help in any way. |
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| Kansas State University did some research using expanded shale. Link attached, fourth article from the top. hortster |
Here is a link that might be useful: Article on expanded shale.
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| Hortster, thanks for the link, I hadn't seen that article yet. I read a few, that's why I'm planning on using it. Today I got the peat moss. They were very generous, I have about 1 cubic yard extra! Anyone in the Twin Cities need some loose peat moss? Maple Grove area. |
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Mctoon - thanks for the kind words. You actually CAN have an extremely productive RB soil w/o the addition of any sand/silt/clay if you wish. The soil you see here was in my raised beds.  It has a little sand and a little Turface MVP in it, but I made the mistake of not adding enough of the mineral ingredients, and had to deal with some shrinkage until I fortified it with the Turface fines that come as a by-product of the Turface MVP I screen for bonsai and container soils. It's now probably the most productive soil I grow in. If you're considering a packaged mineral component, I think I'd give a serious look at Turface Quick-Dry. It has tremendous internal porosity, an excellent CEC, won't compact, always drains well, and holds as much or more water than loam, mixed with organic amendments. Using ingredients with large particles like Haydite & some of the others, just isn't going to give you what you're looking for. Used in small fractions, they don't significantly alter drainage or aeration; in fact, they sort of just take up space. Used as significant fractions of the whole, they're just TOO large to be suitable because they'll drain too fast and dry out too quickly. Al |
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| Al, I went to the stockyard for the Expanded clay this morning and had a look at the stuff in person. It is about the same size as the turface in your picture, like slightly large grain sand with fines, so I got it. I paid $71 per cubic yard, about half the cost of vermiculite best prices. Does that beat Turface price? So, Al, what about the recipe? I know you have a different recipe but I haven't been able to find it again in your many posts. |
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| Turface is about $10/50 lbs, which is a little under 1.5 cu ft. What you have should work fine for annual plantings or veggies if you're willing to replace the shrinkage you're sure to get as the large organic fraction gasses out. I think you'd probably be happier with a higher % of mineral particulates, like fine sand or topsoil. Two things to watch for with the large organic fraction are N immobilization and high soil temperatures (due to ongoing composting) - especially if the compost isn't finished. Al |
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| I paid $2.60 per cubic foot of expanded clay, about half the price of Turface. The description on the website calls it calcined clay which is the same description for Turface. Below is a picture of the expanded clay I got. It's odd to hold it since it's noticeably lighter than expected.
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| Looks good - that's about 1/5 the price of Turface. Do you know the product to be freeze stable? Al |
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| mctoon, thank you for this thread. I have the problem with to much sand(wish we could trade a few truck loads). I am going to add clay (maybe the Turface that Al uses) to hold water in one bed, bio-char in another & may use coco coir in another. |
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