http://ask.metafilter.com/159336/Is-it-possible-to-make-knox-gelatin-stay-a-gel-in-warmer-tempratures
September 28, 2010 12:28 PM Subscribe
What is a gel-like material that I can use to suspend plant fertilizer so that it will release slowly over time?
Someone at work is doing a "helping plants" school project with their kid and the kid had the idea of mixing fertilizer into a gelatin solution and then putting the solid gelatin in a plant's soil as a slow-release plant food. I assume this has been done commercially, but they want to do it from scratch.
They tried gelatin but it melts too easily. I was going to suggest agar (after reading a related AskMe) but I don't know if that will work.
The ideal substrate will break down over a period of days or weeks (maybe when the plant is watered) and is something that a 10-year-old and her mom can make from basic ingredients.
Someone at work is doing a "helping plants" school project with their kid and the kid had the idea of mixing fertilizer into a gelatin solution and then putting the solid gelatin in a plant's soil as a slow-release plant food. I assume this has been done commercially, but they want to do it from scratch.
They tried gelatin but it melts too easily. I was going to suggest agar (after reading a related AskMe) but I don't know if that will work.
The ideal substrate will break down over a period of days or weeks (maybe when the plant is watered) and is something that a 10-year-old and her mom can make from basic ingredients.
Best answer: The polyacrylamide gel that serves to absorb liquid in disposable diapers, and is used to slowly release water for plants and in cooling neckbands, might work for this, if they rehydrate the crystals from a clean diaper with water that has the fertilizer in it. They'll need a control, for comparison, in which he uses the crystals without fertilizer, because the water retention properties of the gel are themselves good for plants.
posted by Ery at 1:44 PM on September 28, 2010
posted by Ery at 1:44 PM on September 28, 2010
Seconding polyacrylamide. It's an awesome science experiment on it's own -- from little kosher salt crystals to big gooey pebbles. And I know they accept food coloring, so the fertilizer should get sucked right in.
posted by freshwater at 6:27 PM on September 28, 2010
posted by freshwater at 6:27 PM on September 28, 2010
Response by poster: Great, I'll try the polyacrylamide. Thanks!
posted by freecellwizard at 6:15 AM on September 29, 2010
posted by freecellwizard at 6:15 AM on September 29, 2010
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The majority of the stick is some mineral that's not very soluble in water. That's how they manage the time release.
For a home project, I think something like plaster-of-paris would be a pretty good choice.
posted by Chocolate Pickle at 1:42 PM on September 28, 2010