Dear all,

I am wondering after how much time of organic agriculture one would expect to run into a deficiency of geogenic nutrients (P, K, etc.).

Let me explain: From what I understand, mineral fertilizers are largely forbidden in organic agriculture and organic fertilizers as manure or compost are sourced from other crops mostly on the same farm. This practice transfers nutrients from less nutrient intensive crops to higher demanding sites, but does not replace the nutrients exported through the harvested products. Those products go to consumers and the nutrients end up in waste water treatment plants and/or surface waters.

As mineral weathering is a slow process, I guess that nutrient stocks in the soils are depleted over time. Please correct me if my reasoning is wrong at some point. I would like to know if there are mass balances estimating this time for different crops/landscapes?

PS: obviously this argument does not hold true for N as it can come from the atmosphere through nitrogen fixing organisms.

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