14 August 1999

Convert to trickle has it taped up

Trickle irrigation has found a convert in one Shropshire grower. Sally Smith reports.

ANDREW Crow couldnt afford a reservoir. Which was just as well. Instead he chose trickle irrigation for his ware and processing potatoes and has found it far better than any overhead system.

So effective has it been that he has increased the area every season over the past five years and eventually he will cease using a raingun altogether. "This season in all I have 26ha (65 acres) under trickle: 12ha (30 acres) of processing and 14ha (35 acres) of ware."

Cropping 283ha (700 acres) on two holdings near Newport, Shropshire, Mr Crow grows potatoes on light sand, black peat and a medium loam.

Irrigation had been by raingun but having suffered water restrictions, he tried trickle on a few acres. The reasons were twofold: there are no supply restrictions for trickle, and initial capital investment does not have to be high. The system can be started in a small way and built up.

That first year Mr Crow chose re-usable tape – an error and one which he did not repeat. Costing more than £495/ha (£200/acre), plus a filtration system, it was effective in delivering the water, giving a good even sample of Wilja with excellent skin-finish and very few rejections: 59-61t/ha (24-25t/acre) sold to local retailers.

However, reusing it was "totally impractical", he says. When he came to lift, he found it impossible to reel up tightly, and there were breaks and leaks. Putting it down again the following year, he found the joiners were bigger than the tape and thus extremely difficult to install.

"We gave up and used throwaway instead. To be fair, the re-usable is much cheaper now; its come down by about 50%, but the throwaway is better for us."

"The second year we used throwaway on 8ha and have done so ever since. Then it was only around £74/ha cheaper than re-usable, but now price is lower, about £345/ha."

This time he tried trickle on Piper, grown for chipping and again on peat, as was the Wilja. The tape was put into the top of each ridge for the Wilja – necessary, he says, if you are going to avoid scab. For the Piper, where he was going for yield, it was run between the rows. This meant he was able to water double the acreage supplied from one tape, saving half the cost. He achieved between 54-56t/ha (22-23t/acre) compared with 121t/ha (49t/acre) from the raingun.

The tape was installed at planting employing a simple machine made in the farm workshop, and still being used. "Just a couple of stanchions and a metal bar going through two rolls of tape, and mounted on the back of the planter. Simple, but it works well." It slows planting down by about 20%.

Reduced costs

By last year, 14ha (35 acres) were under tape. Costs are reducing all the time. Mr Crow estimates the throwaway represents about 10% of his costs.

Two years ago he tried pipes as well. An Israeli Ram 19 cost £19,000 for 10.5ha (26 acres) all in, with a 10-year life expectancy.

Installed in a semi-bed system, one line was run between two and raised by about four inches to deliver water a third of the way up the bed. Processing Piper yielded between 54-56t/ha (22-23t/acre) sold.

Three years on he is equally pleased with the pipe which shows no sign of wear and appears to be infinitely capable of being cut and joined; the connectors fitting easily and well. Reeling up 10.5ha (26 acres) onto 12 reels, he says, takes a man a day and a half.

Capital cost apart, skin finish dictates the continued use of tape on his soils, and it is effective. Such was the quality of the Wilja in 1997, the year of the potato glut, that he could have sold double the tonnage. "If I were in Hereford, say, with the right soil to control scab, I would probably simplify and use pipe throughout. But for me it is not an option."

The water is all pumped from a nearby river by a two-stage diesel engine. A new computer system, the Rainbird, overcomes the disadvantage of trickle: having to monitor regularly, and switch on and off to prevent over-irrigation.

"Programming took a bit of getting used to, but its now working really well. I still check the irrigation frequently, but I am not tied to a specific time.

"Im not just saving water, Im using it more effectively: with 95% accuracy. With a raingun you can lose as much as 30% on a windy day. Overall the trickle uses between 25-30% less than a raingun.

"But it is the fantastic even crops that have so impressed me. Theres not so much as half a tonne of rejects out of 25t."

Mr Crow may yet have to dig that reservoir; trickle may not escape water restrictions for ever. But whatever the water source, hes convinced this is the best technique for irrigation.