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One way to feed the globe's growing population is to ramp up intensive farming in tropical regions, but doing so will require a lot of fertilizer -- particularly phosphorus. This is not only because it is often present at very low levels in tropical soils, but also because many of these soils bind added phosphorus fertilizer, making it less available to crops.
A new study in Nature Plants estimates that intensifying farming on the world's phosphorus (P) binding soils could annually sequester in soil 1 to 4 million metric tons of P fertilizer. For comparison, approximately 2 million metric tons of fertilizer phosphorus are used in North America each year.
Furthermore, the authors found that even after fertilizing for decades, farmers on P-binding soils will still be forced to pay this "P-tax" every year, tying their success or failure to the production, distribution and cost of a finite resource found largely in just a handful of locations around the world. By 2050, the "P-tax" could double if the expansion of the world's tropical cropland area continues.
http://www.sciencecodex.com/phosphorus_tax_could_be_huge_if_tropical_farming_intensifies-180434
http://phys.org/news/2016-04-intensive-farming-tropics-require-huge.html