Granite rock dust will do the job and last for decades. Otherwise, look for 'rock phosphate', which is another mechanically produced crushed rock fertilizer but is much higher in phosphorus content. Also lasts for several years. General horticultural rock dust would also work. All the above will also supply trace nutrients.
A trowel in the hand is worth a thousand lost under a bush.
patpari
Posts: 38
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If you live in Derbyshire, as I do.