I make my own potting soil because it's a way to use my compost, it's cheaper, and I like the idea of it being more sustainable, etc. But I'm finding that at least some plants don't do as well in my potting mix compared to a commercial one. I decided to test the idea with two pots of parsley seedlings from the same punnet. The pots were same, size, placed next to each other, etc. The one with the commercial mix has plants that are now twice the size as the one with my own mix. So that's a pretty clear indicator that something is off with what I'm doing.
My first thought was that pH problems might cause nutrients to be less available in my home made mix. So I bought a less-cheap-but-still-cheap pH meter that measured both mixes at 7.0. I doubted that, so got out some vinegar and bicarb soda to do a basic test and neither visibly reacted with either mixture, so maybe the pH of both is actually neutral. There goes that idea.
I'm not sure what else I can try to measure to work it out. I've considered adding fertilizer to my mix in varying amounts and seeing if I can see a difference in plant growth: maybe my mix doesn't have enough nutrients in it, but if it has too much I guess I won't see that.
My mixture has, in roughly equal proportions,
- compost (mix of worm castings and compost from my tumbler)
- coconut coir (much cheaper than peat moss, where I am, also more sustainable, I gather)
- vermiculite.
Plus it always ends up with a bunch of worms in it from the worm farms.
Does anyone have any ideas? This is bugging me!
My first thought was that pH problems might cause nutrients to be less available in my home made mix. So I bought a less-cheap-but-still-cheap pH meter that measured both mixes at 7.0. I doubted that, so got out some vinegar and bicarb soda to do a basic test and neither visibly reacted with either mixture, so maybe the pH of both is actually neutral. There goes that idea.
I'm not sure what else I can try to measure to work it out. I've considered adding fertilizer to my mix in varying amounts and seeing if I can see a difference in plant growth: maybe my mix doesn't have enough nutrients in it, but if it has too much I guess I won't see that.
My mixture has, in roughly equal proportions,
- compost (mix of worm castings and compost from my tumbler)
- coconut coir (much cheaper than peat moss, where I am, also more sustainable, I gather)
- vermiculite.
Plus it always ends up with a bunch of worms in it from the worm farms.
Does anyone have any ideas? This is bugging me!