A SWITCH FROM rain gun irrigation to an automated drip system for potatoes has significantly lifted saleable output on land in the Scottish borders.

Drip irrigation has raised marketable yield by more than 20% in Maris Piper, and by over 10% in King Edward, reckons Greenvale AP”s growing manager, David Lawson.

His conclusion is based on trials on 24ha (60 acres) last season. The cost of installing and managing the system was 1200-1500/ha, with all equipment on a hire basis.

The firm supplies two big supermarkets with potatoes grown near one of its main sites at Duns, Berwickshire. Quality is very important, stresses Mr Lawson.

“Finding ways to increase marketable yield is one of our main aims, and we are very pleased with the drip system.

 “We need to meet our contracts, and supermarket standards are getting tighter every year. There has also been a slight yield improvement, but that is only considered a side benefit.”

Impending water use laws have also influenced the policy change. “After next year, the Scottish Water Framework Directive will require growers to apply for irrigation licences. I imagine they will look more favourably on cases where water is being used efficiently.

“If we are putting the same amount of water on the crop as before, but getting more saleable yield, then it is bound to help with our licence application.”

Drip irrigation was particularly appropriate last season, he notes.

“It was very dry early on. Applying small quantities of water at frequent intervals gave us the ability to control soil moisture precisely and discourage scab.

“With rain guns it is hard to get water to the tubers which are in the middle of the drill. It tends to run down the side of the ridge, also causing soil erosion.”

While profitability is likely to be greater with the Maris Piper, the response has been more marked for King Edward.

“King Edwards throw a lot of tubers. I expect the variety has responded so well because drip-feeding the tubers has accelerated growth,” he says. “However, I have also been impressed with the Maris Piper results. The drip-fed crops of both varieties have been the best we”ve ever grown.”

Now the company may buy a complete drip system for the coming season for use on targeted fields.

“Installing a drip system does create a lot of work, especially in early season, though once it is set up it is very user friendly.

“I have included a management charge to account for the extra time I have spent, although I am sure labour costs will come down as our knowledge of how to get the best out of the system increases.

“It seems to work best used on the flatter fields, although I am told it will operate on up to a 5 slope. Pumps can be used to get water up a steeper incline.”

Applying water little and often has also helped to reduce disease pressure, he notes.

“In a dry spell, excess water from rain guns evaporates, creating a micro-climate where blight can thrive. Drip systems get the water below the surface and wet the area immediately around the plant, lowering humidity.

“We can justify the expense for King Edward and Maris Piper, because they are high premium crops, and we need to avoid scab at all costs.

“I am convinced drip systems encourage crops to mature quicker, by creating a more consistent growing pattern.”

wendy@sykehall.freeserve.co.uk