Hi everyone! I'm new to permies.com, not new to organic gardening, but just starting to dive into more permaculture techniques. My husband and I just moved to our place in the country about 6 months ago, and we are getting ready to landscape and put in our garden. Our land was just full of weeds taller than me, so we chopped all those down, and now have an open slate. I don't want to put any grass in, so in our front yard area we are planning to do edible landscaping, with raised beds surrounded by some kind of granite, lava rock, flagstone....we are looking into our options right now. My husband just found out that we can get slag pretty cheap, but I am not sure on how it is processed. I know it is produced by smelting ore, but all I can find on the internet about whether or not I can put it around an organic garden is that it can raise the ph of your soil (which would be good around here, because our soil is very alkaline). Does anyone have any info on that for me? By the way, this is not a crushed slag, but one that is more in a "rock" form.
I would be very careful about using slag , by slag I mean the waste of metal production from ores. Firstly it is very veraible. secondly what process made it ? Lead smelting for instance would not be as good a slag as iron blast furnace type slag ? I am not sure if it would be acidic enough either .
Living in Anjou , France,
For the many not for the few
Like David said, be careful about using it. The slag could be mostly innert calcium silicates or it could be quite nasty if it was generated from smelting lead, zinc, copper, etc. ores. Slag can easily be laden with heavy metals. The type of smelting also affects what the slag is comprised of.
I live near an old mining town where some people used 'free' slag and tailings for driveways and backfill. 30+ years later, some of those residences had to be remediated along with the mine and mill sites. Importing a little slag probably wouldn't put you in that situation - but be wary of free and low cost materials that are actually industrial waste products.
Also, you mention it can raise pH. If your soils are alkaline like you say - they already have a high pH so it is possible the slag could make the soils more alkaline. The pH of the slag depends on the type of ore being smelted - so unless you have more specific information you can't predict if it will raise or lower pH.
I'd be afraid to use it.... There's too much free/cheap "good stuff" available. Manure from farms, spoiled hay and straw...Maybe a little sweat equity? I haul veggies over to the guy who gives me the free poop.