25 August 1995

Protection for tubers is more than skin deep

SOARING prices have focused attention on potato quality more strongly than ever this year. Ensuring good skin set before harvest is a vital first step.

"We know very little about the skin and its strength, but our research is beginning to provide new information to help producers and consumers," says SAC potato specialist, Simon Bowen.

Three years of testing has shown consistent differences between strong skinned varieties like Record and Desiree and weak skinned ones like Pentland Squire and Cara.

There is also a strong link between skin set and stem death. Trials show sulphuric acid and diquat applied at the first stages of natural senescence give better skin set and therefore resistance to scuffing than flailing or natural senescence, says Dr Bowen.

Temperature is also important. Skin set in three varieties was faster at 10C than 4C. However, there is no clear effect of soil moisture. Dr Bowen says that destroying haulms while soils remain warm is best for skin set.

Fertiliser usage also has an effect. "Increasing nitrogen for Cara from 100 to 150kg/ha increased scuffing damage by 6%. Increasing potash from 170 to 310kg/ha increased damage by a further 4%.

"We have also shown that using chitted Cara seed reduced damage by 10%. We have, therefore, proved that advancing crop maturity by chitting and avoiding excessive applications of fertiliser can reduce damage, especially in susceptible varieties," says Dr Bowen. &#42

Ensure good skin set to protect potato quality, urges SAC adviser Simon Bowen.