Don't know if you get LANDWARD in England? Sort of like Countryfile and deals with general veggie growing quite a lot too. anyway this morning they were highlighting the SEER Centre which has been researching into the use of rock dust for regenerating the soil with marvellous results. Carrots which stand in the ground all winter, potatoes very resistant to blight, scab etc. but can't find if it is obtainable by the gneral public
Apparently the rock dust is very high in minerals and trace elements from thousands (millions?) of years ago and is obtained from quarries. The Soil Association and other organic bodes are very keen too. Google The Seer Centre for more info - some of the other Scottish people on here may know it as its in Perth I think.
There's some on soil remineralisation here too - http://www.organicgarden.org.uk/remineralisation/index.htm (http://www.organicgarden.org.uk/remineralisation/index.htm). Dunno - but it sounds very interesting.
All best - Gavin