Potash Development Association

It is recognized that crop response to applied N is below the optimum unless there is a sufficient supply of potash. Although specific ratios are not given, there is helpful information in free leaflets, including PDA (1999a, b) and PDA (2001), obtainable from the Potash Development Association http //www.pda.org.uk... 

The Potash Development Association (PDA, 2000) reports that assessors in the US regarded the BCSR concept as most applicable to highly weathered soils of low pH requiring relatively major adjustments in fertility and where high Mg levels need to be maintained. As there are few such soils in the UK, it is questionable as to how applicable this concept is to the majority of UK soils. 

PDA (1999a) Potash and Biosolids. Technical Leaflet No. 20. The Potash Development Association, Laugharne, Carmarthen, UK,... 

As already noted, it is possible to make caustic soda or potash directly at normal commercial concentrations in mercury cells, and in that case evaporation is unnecessary. Diaphragm-cell liquors, on the other hand, present a large evaporative load when 50% NaOH is to be produced. The evaporative load associated with membrane cells is much less, and it is at least conceivable that efficient membranes will be developed to produce commercial concentrations directly. An understanding of these differences is critical in economic comparisons of the various cell technologies. Comparisons of evaporator... 

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