I am about to grow my first potatoes due to being in isolation .I have my huge bag half filled with a mixture of top soil and compost with stones at the bottom for drainage .I have bags of mature chicken manure and some duke of york seed potatoes .Where I am stuck is that I have no idea how much Chicken manure to use and if I place some under each seed potato .I know I plant then eight inches under the soil .Its just how much manure to use and where to place it thats getting me .All help appreciated and hope you all get through these tough times .Thanks a lot

Any manure should be mixed, thoroughly, in with the soil they are being planted in well before you plant.

What are you actually going to plant them in, diameter, depth?
Too much manure, mature or not, will give you lots of vegetation and few potatoes.

Thank you very much .Its just knowing the amount to mix in thats getting me .Lets say how much manure per kg of clay and compost mix .

How many pounds or ft cubed do you have of soil, of any type?
2.2 lbs. to a kilo.

The only thing that really matters is not using too much manure; just mix the soil components together and go from there.
This is a crap shoot guess but, if you have one yard cubed, or one metre cubed, 3 ft by 3 ft, a little more for metres, I would add six heaping handfuls to that amount and go from there.
If you have less add less.
First year -- learning year.

After that potatoes need water, not more fertilizer.
Potatoes grow up from the seed potato but you should have good 300 mm of dirt under the potatoes.
What are you growing this in?

Thank you .I am growing in large bags .The type used for bulk animal feed .My son sowed on the ground as a school project and there was wire worm .Thats why my venture is with clay and compost sourced externally and using the large bags .The fertilizer is Chicken manure seven years old sourced from a friend .No way of checking anything scientifically so going by gut feeling and of course your advice .We will see how it goes and thanks again .Passing the time for me during this crisis .

Hi Johnny. Where are you located? Personally I would avoid using chicken manure if growing in bags/containers.

The most important thing to remember when planting in containers is that the roots of the plants can only go down so far. Make sure your containers are deep and wide enough to accommodate your vegetables. For example, most of my vegetable containers are approximately 12 to 14 inches wide and 10 to 12 inches deep. Depth is especially important when growing root vegetables, such as potatoes.