Is this a potassium or magnesium deficiency?

Potassium deficiency

Thanks! I was doubting because we have a clay soil, does it make sense to correct it?

Yeah

Spray fungicide too

I just applied a 3 4 10 organic fertiliser. I mainly wanted to exclude a magnesium deficiency because excess potassium prohibits magnesium uptake. Thanks again for your answers!

See this and identify

Bram Van Breugel

Bram Van Breugel

The upper leaves are indeed doing just fine does Phosphorus and magnesium show the same mobility as potassium? Since I'm just managing my home garden and not a whole field I won't be sending soil samples to a lab. I guess the conclusion is that it's difficult to distinguish ;)

You can checkout the 1 pic that is same to your problem

Ok, I neer to start looking a bit better, initially I thought to see these wedge type shapes shown for magnesium deficiency. But you are right indeed that it better resembles the one showing potassium deficiency ;) thanks a lot for your persistent help!

Overall the Vine is doing ok by the way but it will start doing better with your help :) thanks!

It my pleasure to help you