yellow patches on tunnel potato

[martint]

sharpes express west of ireland
plants about 1foot tall most look good, are patches sign of deficiency?

[Slashhook]

Hello Martint

Yellow spots forming on the leaves of your potatoe plants to me would indicate they could be suffering from a magnesium deficiency. If this is the case they will recover if you spray them with magnesium sulphate (Epsom salts). You can buy it in the chemist. Dissolve 2 teaspoons in a pint of water and spray them well every day for a week. If this is the problem you will see results quickly. I have found this link useful Color Pictures of Mineral Deficiencies in Potato Plants Also I wouldn't plant them anywhere that tomatoes have grown in at least the last year.
If there is too much potassium in the soil, the plants absorb that instead of the magnesium. Good luck with the crop

[Kristen]

You can buy it in the chemist.

... or a garden centre (which I would expect to be cheaper - larger volume bags)

[martint]

Sounds like good advice, will try. Thanks

[King Carrot]

I'm growing the same variety in a cloche, a fair bit south of you I suppose. Two plants of mine have a touch of yellow on their leaves from frost/sun damage during a light frost last week - there's a small gap at the end of the cloch and the two plants at the end of the row are affected on 2 or 3 leaves.