Potato Fertiliser - How much to use in containers?

[starloc]

I havent fertilised potatoes unless I was growing in pots but I am planning to this year, I just bought 25kg of the spuds galore one from ebay for about £30 to try it, the npk looks correct

[bario1]

I bought the P£land stuff too, it has an NPK of 4-2.5-2.3 (whatever that means) and recommended usage is 140g/metre.

[Jonnyt]

Given mine is 12-11-18 it looks like you only need 1Kg for every 4Kg or more of the Poundland stuff so actually is cheaper than the Poundland stuff given I got 2.5Kg delivered for £8.18

In fact if you look at the composition of the Poundland stuff it's not got enough K which is whats required for the tubers

[Kristen]

I bought the P£land stuff too, it has an NPK of 4 - 2.5 - 2.3

Vitax site is silent on what the NPK of their product is - I find it extraordinary that companies like that don't have detailed product descriptions - surely they don't want everyone wasting their staffs' time phoning up to ask?

Organic Potato Fertiliser | Vitax

Only site I found that published it said N.P.K: 4 : 2.5 : 8

Vitax Organic Potato Fertiliser 1kg - Gro-well Direct

Researching what Potatoes need I found articles that suggest an NPK of 1 : 1 : 1.5 - i.e. 1.5x as much Potassium(K) as Nitrogen(N) and Phosphate(P) - so 2:2:3, 4:4:6 or anysuch ratio would do (higher numbers just mean that the product is more concentrated / less needs to applied)

So Vitax NPK of 4 : 2.5 : 8 is roughly a ratio of 2 : 1 : 4
and Poundland NPK of 4 - 2.5 - 2.3 is roughly a ratio of 2 : 1 : 1 which I think is rather high on the Nitrogen side, particularly if manure has also been applied, but definitely low on the Potassium side

On an acid soil applying wood ash would boost the Potassium somewhat (and raise the pH - thus best avoided on alkaline soils as higher pH would encourage Scab), or line the planting trench with Comfrey leaves to provide Potassium growing growth

For main crop it apparently helps if some Nitrogen is added later in the (longer) growing cycle - e.g. when the leaves are close to touching their neighbouring plants - because Nitrogen applied earlier is likely to have been used up, or washed out of the soil. If Comfrey is available then make applications of liquid feed whilst the tubers are bulking up. Alternatively apply some Sulphate of Potash feed instead of Comfrey during the later stages of growth.

[bario1]

The Poundland stuff also says it has +9.3% CaO - what's that?

[mrswadders]

calcium oxide - commonly known as quicklime

[Jonnyt]

So the spuds galore is the perfect mix

[starloc]

I ordered the spuds galore 25kg sack and they delivered with the original bag, there is info on the manufacturers site about nutrition for crops at various times, remembering that you dont necessarily want so much fertilliser that it tastes like a shop bought potato...

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[Jonnyt]

Very interesting that link. It would seem the same stuff is used commercially for Onions at 50g per Square Metre as well