This is true. However the little-known fact is that healthy soil contains all the "machines" required to break down the abundant insoluble potassium (along with every other necessary element) present in rock particles into plant-soluble fertilizer. This "insoluble pool" contains enough nutrients for literally thousands of years of plant growth, if only the soil life is present to unlock it.
The problem is that tillage kills this soil life, and that dead land now requires the constant import of external fertilizer to grow food. Pesticide and fertilizer application also kills these organisms, which out-compete pest species (as mentioned here: https://news.ycombinator.com/item?id=15515209). Spraying becomes a vicious cycle for the farmer, and a lucrative cycle for their chemical supplier.
In other words, functional soil isn't just an inert "tank" for holding nutrients. It's a two-dimensional factory for converting in-situ rock and air and rain into biomass.
This is all explained much better by soil microbiologist Elaine Ingham. https://www.youtube.com/watch?v=x2H60ritjag
> luckily engineers and farmers are looking at these things more closely now.
I would add biologists (including soil scientists, botanists, mycologists, entomologists, ecologists, etc) and indigenous experts to that list.
farmers do add fertilizer and other stuff back to the soil, though we are finding that maybe there is more to the equation. certain methods like tilling are done to kill parasites, etc, but it may also make the soil vulnerable to erosion. luckily engineers and farmers are looking at these things more closely now.
its also important to note this is just 1 study. just 1 region. 1 particular type of trap. there is still lots to know / find out, but I think its wrong to be jumping to huge conclusions just yet.