16,800 posts on Compost, I gave up searching and did a new post, apologies...
We have been making compost for ten years but the resulting compost doesn't work well as a substrate. The harvested compost turns dry and hard and crumbly and our plants don't thrive in it. Help!
My hypotheses for what may be going wrong:
- Too much kitchen waste and not enough carbon - the compost is mostly kitchen waste that we "mulch" with either coffee chaff, sawdust or dry fallen and partly decomposed cypress needles. We don't have a huge amount of garden waste to add, most of our garden is covered in tradescantia which is unkillable and I don't want to give it new cushy homes in the compost.
- Too acidic: my husband decided that the compost needs a pre-digestion stage and we now start the compost in an airtight barrel, where it pretty much ferments. Weirdly, this sometimes seems to preserve the waste rather than breaking it down, like a giant mango peels and carrot tops kimchi. When the barrel is full we turn it out into the aerated compost bin, and it stinks (sour, not putrid) for a couple of days.
- Too acidic from those cypress needles: the compost bins are under a big cypress that drops plenty of needles all around. Many of those are decomposed and I often grab a handful of them for covering up the kitchen waste. But might they still be "active" and allelopathic, like pine needles?
- We have lots of earthworms, both pink "Californian" ones and grey, vigorous native ones (living in southeastern Mexico). Can the earthworms have eaten all the nutrients?
I just emptied out a second-stage compost (the areated bin where the fermented stuff had already broken down, full of earthworms) and it seemed perfect: moist, dark brown, fibrous, easy to pull out the avocado seeds and maize fibres that hadn't decomposed yet. I used this for sowing some seeds and for some potted plants. But where we've used the last batch of compost the plants don't seem happy, the soil forms into little gravel-sized nodules.
Context: we live in a town in Chiapas, Mexico, at 2200 m altitude. It's dry from October to April with cold nights and strong, lethal sun. From May to September it gets warm and rains nearly daily, often with crazy deluges. The soil is thick unbudgeable red clay and we're planting on top of that and building rubble, slowly creating soil. We're adding plenty of mulch and cover crops which in turn invites snails and slugs. Sigh. Special plants need to be nurtured indoors where it's an all-or-nothing laser sun or shade situation, hardly any indirect light. The sun weakens the plants and they often succumb to (I think) powdery mildew. Sheesh.