Depending on what you consider natural and efficient.
If mining is natural there is some volcanic stuff that is nutrient rich. If by natural you mean organic, compost piles produce good fertilisers but they are not as efficient as some might say. They take quite some time to complete their process and get it’s nutrients available for growing plants. Not being efficient doesn’t mean they aren’t good. They are a great way to dispose or organic material and even if compost releases its nutrients very slowly it contributes to the soil health in many other ways that I would say are more important, like increasing biodiversity, making the soil more resistant to changes in pH and facilitating retention of nutrients so they don’t wash out with rain.
Depending on what you consider natural and efficient.
If mining is natural there is some volcanic stuff that is nutrient rich. If by natural you mean organic, compost piles produce good fertilisers but they are not as efficient as some might say. They take quite some time to complete their process and get it’s nutrients available for growing plants. Not being efficient doesn’t mean they aren’t good. They are a great way to dispose or organic material and even if compost releases its nutrients very slowly it contributes to the soil health in many other ways that I would say are more important, like increasing biodiversity, making the soil more resistant to changes in pH and facilitating retention of nutrients so they don’t wash out with rain.