Economy key in irrigation and spray trials

Advances in trickle irrigation achieved 40% water savings in Kent farm trial, Brian Lovelidge reports.

Fruit Focus visitors inspect some of the 70,000 plants of EMR's new everbearer Finesse - image: Brian Lovelidge
Fruit Focus visitors inspect some of the 70,000 plants of EMR's new everbearer Finesse - image: Brian Lovelidge

A trickle irrigation system developed at East Malling Research (EMR) has achieved 40 per cent savings in water and fertiliser use in a trial on protected June bearer strawberries on a Kent farm this year. The trial is part of a five-year HortLINK project that in 2011, its final year, will be extended to a number of other farms with a wide range of soil types.

Details of this work, funded by Defra and the industry, were given by research team leader Dr Mark Else during a tour of EMR research projects at Fruit Focus last month. He stressed that the need for water savings is increasing apace with the demand for the nation's finite supply expected to rise by 30 per cent by 2050.

A questionnaire on water use sent by EMR to strawberry growers showed that it averaged 78 tonnes per tonne of class 1 fruit. But some of the more water-conscious respondents used only 45 to 50 tonnes. Those at the other extreme used more than 120 tonnes, indicating that considerable savings are possible.

"We want to match the crop's water supply to demand but in changeable weather that's very difficult," added Else. "To provide insurance, growers tend to keep the soil fairly wet, but that's not using water and fertiliser efficiently because some runs to waste.

"We'd like to bring down the average from 78 tonnes to 50 tonnes or even less," he continued. "Our best trial result here is 10 tonnes but that's not realistic with much larger-scale production."

His team has developed a system using very accurate soil moisture probes and other electronic equipment that closely matches trickle irrigation input to the crop's water requirement.

In this year's farm trial, on a sandy loam soil, the system was used in three polytunnels and the results were compared with the grower's usual irrigation regime in three other tunnels, in which a neutron probe was used to measure soil moisture in the soil profile.

Despite being one of the more water-conscious growers, by the end of the trial he had used 22 hours of irrigation against the EMR system's 14.5 hours, noted Else.

Furthermore, the EMR system's fruit was up to 50 per cent firmer than the grower's, giving it a better shelf life, although the Brix readings for the two samples were more or less the same. Crop yields were still being assessed at the time of the tour. "We sent samples of the fruit to Waitrose for taste tests and it preferred our fruit," Else claimed.

EMR is also developing a telemetry system that enables data generated by crop water-use instruments to be remotely accessed and irrigation trigger values to be set. This information can then be used by a computer programme that indicates when the values have been reached and, if required, the irrigation switched on remotely.

Another five-year HortLINK project, with the same funding, on minimising pesticide residues on strawberries, started in April 2008, was described by its leader Professor Jerry Cross. His team is developing methods of controlling the crop's most serious pests and diseases, such as powdery mildew and the European tarnished plant bug, with much reduced or nil use of pesticides.

"Mildew is serious in strawberries in a tunnel environment," he affirmed. "We've been looking at where the infection comes from and we found that in cold stored runners from various sources the mycelia are almost entirely killed out so the disease must be coming from (nearby) infected crops.

"There's a tendency for growers to routinely spray against mildew every 10 days or so but we've developed a computer model made into grower-friendly software that predicts (the best) spray timings. In trials this season, this has halved the number of sprays required to control the disease."

Botrytis is another very important disease his team is working on, although it has found that the risk of infection on June bearers when covered early is greatly reduced. Cross said this posed the question of whether sprays against the disease are needed at all or can be reduced in number.

This possibility has not yet been tested, however. Meanwhile, he has been investigating the use of bees to transfer specially formulated bio-control agents to strawberry flowers. The bees pick up the agents containing Trichoderma and Cladosporium from dispensers at hive entrances.

"The agents are quite well dispersed but we've not yet demonstrated that they lead to good Botrytis control," he admitted. "We've also developed a Botrytis computer model that predicts the risk of infection of the flowers and when there is a need to spray. The model will be used in large-scale grower trials next year."

His team is also assessing numerous minimal spray techniques for controlling significant pests such as the European tarnished plant bug, the strawberry blossom weevil, aphids and the western flower thrips. The measures developed in the project's first three years will be used as part of an integrated pest and disease management system to be tested and refined in grower trials in the remaining two years.

EMR strawberry breeder Dr David Simpson told Fruit Focus visitors that his programme has been funded by the Strawberry Breeding Club for the past three years. In future, the club will be taking over the commercialisation and on-farm trialling of new varieties from Meiosis. However, because his new everbearer Finesse was bred before the club was established, Meiosis has been responsible for handling it.

The visitors saw 1.8ha (70,000 plants) of the variety planted for commercial production at EMR. The fruit is being supplied to Sainsbury's and it is also been listed by Tesco. The hope is that other supermarkets will take it up, said Simpson.

One of Finesse's advantages over many existing everbearers is that it has no proprietary rights so it can be planted by all growers irrespective of marketing groups.

Simpson claimed that Finesse plants are quite robust and hold their attractive heart-shaped fruit on quite long stalks that help speed up picking. Furthermore, they produce very few runners, which reduces the time spent on their removal. "This trait initially proved a headache for propagators," he said. "Although they have now got over it."

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