If for no other reason, is terrestrial agriculture on Planet Earth ultimately phosphorous limited?

Question

The following outlines the question in the context of a PhD dissertation:

1. As far as I know, all life requires phosphorous (Epiphytes the least of all.).

2. In a plant the predominant pathway of phophorous to the plant is in aqueous solution to the roots.

3. What phosphorous that is not ephemerally received by the plant roots is either leached as a soluble compound below the root zone of the plant or, in the case of certain clastic soils, so chemically bound to the soil particle as to be only released with a decline in the pH by, you guessed it, acid rain, in which case the former process of leaching to below the root zone kicks in, again.

4. If we recyled 100 per cent of all plants produced for agriculture, some fraction of each recycle will be lost forever below the root zone by leaching.

5. Nature's pre-agricultural balance of phosphorous was achieved by, you guessed it, the distribution of phosphorous laden ash from the natural (lightning-induced) combustion of plant materials growing in soils where the perennial water table is at or above their root zones. The hydric and the wetter mesic soils supporting emergent vegetation on the planet have been the means of phosphorizing the plant life on the drier mesic and the xeric soils of the planet.

6. Now here is where the PhD dissertation comes in: The mining of phosphorous for application to terrestrial crops upon the later group (dry mesic and xeric) soils is an absolutely terminal end game: There is less and less minable phosphorous being spread over more and more phosphorous deficient real estate with no way to jack up the water table to the root zones of the plants in order to artificially capture the phosphorous in a 100 per cent recyclable terrestrial agricultural regime.

7. So our PhD crew will look at the numbers of how this cycle (mining, leaching, etc.) will degrade over the years and the options for turbocharging the use of the planet's high water table soils for the final bread basket of humanity...or how to achieve a broader bread basket through the use of hydroponics of all sorts (fresh and salt water) to make up for the difference so that we are not committed to wiping out the Everglades just to grow tomatoes in a sustainable phosphorous cycle.

Answer 1

I can't figure out if you are asking a question or trying to tell us something.  But to answer your question, no, I don't think that agriculture is ultimately phosphorous limited.  While the amount of phosphorous that can be mined is limited and the amount of chemical phosphorus fertilizer available may be limited, agriculture will have to turn toward more organically recycled phosphorous supplies.  Will it change the way of farming as it now exists, yes.  But I am worried about a lot more things limiting our agriculture and ultimately our food supplies ahead of running out of phosphorous.

Answer 2

I think you are right as the phosphorous cycle - fish to guano to fert to food to sewerage to fish may take several millenia so we may be doomed! We need to recycle our sewage.

Isaac Asimov wrote  in detail,  (with all the inputs and outputs,) about this in one of his books - I can't remember the title but I think it was from the 50's or 60's - very interesting.

Answer 3

I don't get it.

P is as important as C, N and O.

Water is also extremely important.

And so is light.

Water is more critical than P.

Answer 4

One untapped Phosphorous source are phosphorous ores at the bottom of the oceans.  Recycle phosphrous supplies makes sense.  Bone Meal used to be considered a good Phosphorous fertilizer, but with the advent of BSE we are probably not utilizing this source as well.