Lookup NU author(s): Professor David Manning
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All plants require nitrogen (N), phosphorus (P) and potassium (K) as major nutrients, from a range of possible sources including artificial fertilisers. Both P and K (and almost all minor and trace nutrients) are derived from mined sources: P from phosphate rock and K from potassium salts such as sylvite (KCl). The reserves of P and K are equivalent to up to 400 years production at current rates, and resources have life expectancies of 1800 and 7500 years, respectively. Prices of K fertilisers are currently very high (US$ 500 per tonne), in part reflecting the cost of mining. However, nutrient audit studies for the end of the 20th Century show that although N is approximately in balance, 30% more P and twice as much K needs to be mined to compensate for that removed by crops. With growing global populations, world production of K needs to triple by 2050 to feed the expected population, whereas P production needs to increase by 70%. In these circumstances, there is a pressing need to broaden the range of available sources of K, especially for farmers who cannot afford conventional fertilisers. Candidates include the silicate minerals, such as feldspars, feldspathoids and micas. Mineral dissolution rates show that feldspathoids dissolve 105 –107 times more rapidly than feldspars, and in contrast micas release K by cation exchange. Given the current high price of K, it is appropriate to consider widely available silicate minerals as an alternative source.
Author(s): Manning DAC
Editor(s): Harrison, R.M., Hester, R.E.
Publication type: Book Chapter
Publication status: Published
Book Title: Soil Quality and Food Security
Series Title: Issues in Environmental Science and Technology
Publisher: Royal Society of Chemistry
Place Published: London
Library holdings: Search Newcastle University Library for this item