Imagine there is a small island, like Malta, and the ecosystem has no external inputs (no fertilizer delivery, etc).
What does a sustainable plant based agriculture system look like? Are there already existing examples?
I’m very interested in how top soil is maintained without external fertilizer inputs?
One area of concern, I have, with modern monocrop farming techniques is the depletion of top soil, with something like 60 crop cycles left before we are current system falls over.
The industrial production of fertilizer is only about a century old (Haber-Bosch process for nitrogen fertilizers). Fertilizers are mainly concerned with nitrogen, phosphorus and potassium.
Before industrial fertilizers existed, people replenished the soil with:
Crop rotation works, because there are also natural processes which replenish these nutrients. For example, this is the nitrogen cycle:
https://en.wikipedia.org/wiki/Nitrogen_cycle
In particular, you can plant legumes, which will naturally bring nitrogen into the ground.
Either plant them as part of your crop rotation, or you can also plant e.g. potatoes and beans close together to continually replenish the nitrogen.
My understanding is that manure, and the crop rotation (three field system) both rely on animals; Does composting provide enough to replenish the soil sustainably?
The Three Sisters method, https://www.nal.usda.gov/collections/stories/three-sisters, has a ruminant cycle in it as well I believe.
I’m not sure, are ruminants acceptable as part of a plant based ecosystem?