Lookup NU author(s): Professor David Manning
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Recently published assessments of nutrient budgets on a national basis have shown that K deficits for developing countries are so substantial that a doubling of world production of potash fertilisers would be required to balance inputs and offtake, simply to meet demands in Africa alone. The price of potassium fertiliser raw materials has increased by a factor of 4 during 2007-2009, approaching $1000 per tonne in some markets. Thus an annual investment of the order of US$5600 million is required to replenish soil K stocks in Africa. In this context it is appropriate to review current knowledge of alternative sources of K, which is the seventh most abundant element in the Earth’s continental crust, present in feldspars and (much less commonly) feldspathoid minerals including nepheline and leucite. Theoretical considerations based on the experimental determination of mineral dissolution rates indicate that nepheline dissolves 100 times more quickly than potassium feldspar, and this suggests that nepheline-bearing rocks are more effective as sources of K for plant growth than granitic rocks, even though these have higher K contents.
Author(s): Manning DAC
Editor(s): Lichtfouse, E; Hamelin, M; Navarrete, M; Debaeke, P
Publication type: Book Chapter
Book Title: Sustainable Agriculture
Place Published: Heidelberg
Notes: This was an invited paper. Springer published it in the journal 'Agronomy for Sustainable Development', and in this book. It uses information from a range of sources to generate innovative approached to solving problems of soil fertility, exploiting the dissolution kinetics of silicate minerals.
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