Pioneering potato growers turn on trickle irrigation

When it comes to growing potatoes using sophisticated forms of irrigation, Lincolnshire farmer David Matthews leads the way.

Unlike many potato growers who apply water using rain guns or booms, Mr Matthews, of G&D Matthews, West Pinchbeck, uses trickle irrigation on the 140ha of Maris Piper and Marfona he grows for the top end of the pre-pack market.

“In the late 1990s, we were convinced trickle was the way forward,” explains Mr Matthews, who manages the business with his son, James. “We could see the benefits for scab control and skin finish that localised irrigation could offer.”

Good water management skills are vital but get it right and the quality dividends of trickle irrigation can be significant. The system can also be used to apply fertiliser and nutrients with the irrigation water.

Water is delivered through disposable tape laid 50mm below each ridge about two weeks after planting. The silty soils are prone to capping so this approach means irrigation can continue under the cap to control soil moisture and prevent scab.

“We normally irrigate on a 1-3 day interval, and have the capacity to irrigate the entire area in 24 hours if needed,” says Mr Matthews. “If it rains, we can delay the next irrigation without worrying about keeping up with crop water demand.”

Trickle irrigation has been used in horticulture for years. But increasing concern over water scarcity means more broadacre growers are considering trickle – despite the high capital investment which means annual costs can exceed £1000/ha.

Earlier this month, more than 50 farmers – including potato and onion growers – gathered in the Fenland market town of Whittlesey for a UK Irrigation Association (UKIA) seminar to discuss efficient ways of irrigating their crops.

Darren Smith, of the Environment Agency, said it was more important than ever to consider switching irrigation methods to save water. Growers with abstraction licences should irrigate crops efficiently if they wanted their licences renewed.

“We recognise that ‘efficient use’ means different things to different people. We take it to mean that the right amount of water – reflecting the needs of the crop and no more – is used at the right place and at the right time.”

At the moment, growers using trickle irrigation do not have to obtain an abstraction licence. But this too is changing. Increasing water scarcity means the exemption is due to be removed – possibly as early as April 2009.

By April 2010, it is likely that all abstractors using trickle irrigation will have to apply for a licence. The Environment Agency will then have until 2015 to decide whether an individual licence application has been successful.

It is expected that only trickle irrigators operating before the introduction of the new rules will be allowed to continue until their licence application is determined – a situation which has contributed to a flurry of interest in the technology.

Mr Matthews is only too aware of the forthcoming changes. “We carefully audit our water use and make annual returns to the Environment Agency. It is important that we demonstrate efficient use of water both to our customers and to the regulator.”

Cambridgeshire potato grower Roger Hunt Pain is testing a trickle irrigation system to see whether it is worthwhile. “It’s too early to say whether there is an advantage in terms of yield or quality but this will hopefully be clear by the end of the year.”

Even other farmers who feel trickle irrigation is a step too far are being urged to reassess their existing water application methods. Rain guns, for example, are often incorrectly calibrated, said independent consultant Bill Basford.

“The biggest single fault is incorrect water pressure at the gun,” he told delegates at the UKIA seminar. “Many more rain guns could be operating much more efficiently than they are at the moment.”

Uniform irrigation using a rain gun was often compromised by inconsistent flow rates, the effect of wind speed and the variable size of water droplets, said Mr Basford. But guns were easy to transport, reliable and cheap.

“There are significant challenges when using a rain gun but there are challenges too with other systems. Growers should think twice before rushing out with a cheque book and buying themselves a whole new set of problems.”