Chemistry Reference
In-Depth Information
7 Conclusions
The world's population depends on adequate supplies of food. At the present
time, food production is mining mineral nutrients from soil in an unsustainable
way, especially for K. Much is known about the occurrence and quantities of
both P and K that exist in the Earth's crust and can be mined as raw materials
for fertiliser production. In the case of P, resources equivalent to 1800 years of
production at current levels are known to exist. P availability is not a major
issue, especially as so much P is lost through waste-water discharges that might
otherwise be recovered. K has resources equivalent to 7500 years, but current
production is half what is needed. This, in part, reflects the geographical and
geological occurrence of K deposits, which occur mainly in North America and
require production from capital-intensive deep mines. K is an expensive
product, inaccessible on the basis of price to many farmers.
It is important to consider sources of K that represent an alternative to
conventional expensive mined products. Potassium silicate minerals, such as
feldspars and related minerals, are abundant and widely distributed globally.
The key to their exploitation and use as sources of K is their dissolution rate,
not their absolute K content. Additionally, micas also occur widely and
provide a source of K that functions through cation exchange. It is reasonable
to assume that necessity will lead farmers in poorer parts of the world to use
silicate minerals as a source of K, in the absence of affordable alternatives.
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References
1. United States Geological Survey, 2010 Minerals Yearbook: Nitrogen,
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2. United States Geological Survey, 2010 Minerals Yearbook: Phosphate
Rock, United States Geological Survey, Reston, Virginia, USA, 2011;
http://minerals.usgs.gov/minerals/pubs/commodity/phosphate_rock/,
last
accessed 04/12.
3. United States Geological Survey, 2010 Minerals Yearbook: Potash, United
States Geological Survey, Reston, Virginia, USA, 2011; http://minerals.
usgs.gov/minerals/pubs/commodity/potash/, last accessed 04/12.
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(RB209),8
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