30 October 1998

Water use assured

More precise water use can

save money, improve yield

and boost quality. Now it

seems it may be needed to

meet produce assurance

scheme criteria too.

Louise Impey investigates

DEMAND for a consistent supply of quality produce prompted a new approach to irrigation and water use on salad crops at G S Shropshire and Sons (Cambs Farms) near Ely.

Four years ago, farms manager Derek Wilkinson recognised the need for a more scientific justification of water use across the 1700ha (4200 acre) farm and an improvement in the accuracy of application.

Since then, the introduction of assurance schemes has proved him right on the requirement for better precision.

With 700ha (1730 acres) of lettuce, 200ha (490 acres) of celery and 300ha (740 acres) of potatoes and onions requiring water, irrigation is used to ensure crop establishment, maximise yields and guarantee quality.

"Continuity of supply is so important to our customers and irrigation has a key role in helping to achieve this," he explains.

"At the same time water has been getting more expensive to apply, both in terms of labour and machinery and a move towards more winter stored water. So we needed to be scientific about it."

Boom irrigators were purchased for their ability to reduce water use through accurate application and irrigation scheduling services from three companies were also employed.

"Were on a range of soil types and our aim is to produce a blueprint for water use for each crop and soil type," says Mr Wilkinson. "And as we use below ground irrigation on the peat soils, its success depends on good management."

Ipswich-based Fullpoint Probe Services began working with Mr Wilkinson three years ago. Soil moisture testing is carried out using both hired and serviced neutron probes and farm-owned theta probes, which are situated in the various crops around the farm.

Fieldsman James West visits twice a week to take measurements of the soil moisture capacity. Those are combined with weather and irrigation data to generate a schedule of irrigation requirements for the next seven days.

The company also carries out soil analysis where required, checking soil structure is not a limiting factor.

"Our information tells the grower when to start irrigating and how much water to apply," points out Mr West. "Some people also use it to prioritise their water applications.

"There is still a tendency to over-water on many farms, so scheduling helps growers make better use of a limited resource," he adds.

Scheduling is charged for according to site and how much of the equipment is hired by the grower. Mr Wilkinson calculates that he pays around £120 for each lettuce crop and £250-280 for a potato crop.

"When you consider that the cost of applying 25mm of water is £70-75/ha, you only have to save one application for the service to pay for itself.

"But our objective was to make better use of water. That doesnt always mean we save applications."

Mr Wilkinson also points out that buying the equipment costs more. "A theta probe costs around £1500 to buy outright and requires us to take the readings ourselves. But Fullpoint helps with the analysis."

For the records

AS Hainey Farm is a LEAF audited farm, a member of the Assured Produce scheme and a Tesco Natures Choice (Gold Standard) farm, the business has been working with Fullpoint Probe Services on the irrigation recording requirements of the various schemes.

"Next year growers will have to document both rainfall and irrigation applications on a daily basis," reveals Mr West. "As rain gauges are installed next to the neutron probes on this farm, all the information is already being kept, so meeting the requirements wont require any additional effort or expense.

"As far as the schemes are concerned, each holding will have to produce a blueprint for growing a crop, part of which will be water use," he explains.