When to fertilise spuds

Hi

This is my first year at growing spuds, I have limited space so am growing in grow sacks. My first earlies have come up now past the top of the sack after earthing up for the past few weeks.

Now should I use a feed at any point to encourage the plant to produce spuds? If so at what point is a time to start?

Any suggestions for what to use if appropriate also most welcome.

Look here http://www.allotment-garden.org/vegetable/potato/potato-fertilizer-programme.php

You can always use the tabs above...click information tab and fill in query box  site then shows you absolutely pages!

You're welcome