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I remember reading part of a PhD thesis about the implications of “peak phosphate” more than a decade ago. (Not my area of expertise, but the guts of it weren’t
by rgmerk 3y ago
I remember reading part of a PhD thesis about the implications of “peak phosphate” more than a decade ago. (Not my area of expertise, but the guts of it weren’t particularly difficult to understand).
My takeaway (though not the author’s) was that it’s way down the list of things to worry about.
Basically, the cost of phosphate is such a miniscule component of the cost of food that it would make essentially no difference if we had to mine lower-grade sources of it.
Higher prices might also reduce the amount wasted as runoff, which also would reduce the environmental damage caused by fertiliser use, something we’re going to have to take more seriously at some point.
- pfdietz 3y agoPhosphate in soil is mostly in fixed, unavailable forms (like ferrous phosphate). Prolonged application of phosphate fertilizer would cause their accumulation. At that point, I think it would be worthwhile to look for ways to tap into that store, for example Phosphate Solubilizing Bacteria (PSBs), or plants genetically modified to perform the same function in their roots. Phosphate removed from fields by erosion or in plant matter would have to be replaced at some point.
- pfdietz 3y agoJust 10-20% of applied phosphate fertilizer is taken up by plants. The rest gets lost in these insoluble forms. So there's a lot of room for improvement here.
- mech7654 3y agoSo for NPK fertilizer, I now know that nitrogen is manufactured cheaply with the haber-bosch process, and we've got a lot of phosphate available. Do we also have plenty of potassium around? i.e. enough to realistically never worry about "peak potassium".
- adrian_b 3y agoSea water contains huge amounts of potassium that is easy to extract. The most abundant rocks also contain huge amounts of potassium, but which is expensive to extract. Neither in nature nor in agriculture potassium is ever a limiting nutrient like nitrogen and phosphorus.
- kragen 3y agoif potassium was never a limiting nutrient it wouldn't be sold as a fertilizer at all, much less be one of the three primary fertilizer nutrients
- adrian_b 3y agoYou are right that I did not express that well, because as said it is true only in natural places, not in artificial cultures. For modern cultivated lands potassium must be indeed used as a fertilizer, because much of what exists in the soil is removed by remaining in the plant parts that are harvested then transported elsewhere. Another part of the potassium may be washed away by intensive irrigation. So the potassium that is taken away depending on the cultivation methods that are used must be replenished. However its abundance is such that this will never be a problem.
- Mistletoe 3y agoI have to object to the last sentence. I’ve gotten lots of soil tests from various locations in soil and greenhouse media where I need more nitrogen (almost always) and potassium (sometimes), but never phosphorus. And I even live in one of the blue states with lower P in the soil. https://pubs.usgs.gov/sir/2017/5118/sir20175118_element.php?el=15 https://pubs.usgs.gov/sir/2017/5118/sir20175118_element.php?...
- pfdietz 3y agoThere's a gardening channel on youtube I watch (RED Gardens) where the guy does all sorts of small scale experiments with organic gardening. He was a bit surprised to discover his soils have excess potassium, from the various organic materials he had been using (like wood chips for mulch; pot ash, right?) The soils were also sodium deficient, so he was thinking of spreading measured amounts of salt! He also discovered commercial compost can be crap, since it hasn't broken down enough and soaks up nitrogen as it finishes its decomposition in the ground. So if your potatoes are struggling in something like that, slather on some urea and they'll perk (and green) right up.
- esaym 3y agoPerhaps I live under a rock, but phosphate is expensive. I was buying diammonium phosphate at $250 per ton a few years ago. Then it went to $340. Then COVID happened and it went to $600. Then the next year it was over $800. The ag supply company didn't even have enough cash to pay for a truck load. They've completely stopped carrying it now.
- eximius 3y agoI'm sorry but you're saying a literal ton, over 2,000lbs, at $600 is expensive? I can't think of any material I can buy a ton of for $600.
- tiedieconderoga 3y agoLandscaping materials? You can get things like sand and mulch for like $30/ton. You just have to provide your own transportation.
- NovaDudely 3y agoSalt is about a third the cost. You can get a 1 ton pallet of salt, processed, bagged up and delivered to a business for far less than $600. It is amazing to see in action.
- jessriedel 3y agoYea. For other's reference: a tractor trailer can haul something like ~40 tons and costs ~$4k to go cross country, so shipping costs from mine to fertilizer processor to farm are already going to be in the general ballpark of $100/ton.
- defrost 3y agoMining, as I've known it, uses Haulpak trucks onsite that each carry > 110 tonnes. They fill a train a day (at least), the trains being some 2.4 kilometers in length carrying some 29,000 tonnes that typically travel some 100km from minesite to coastal port. Ship capacities are 380,000 to 400,000 tons deadweight and travel about the globe. "Tractor trailors" (or two to three trailer road trains) as you're describing are used to bring food and supplies and general light goods too and from a minesite. There are such things as economies of scale.