EMR tours reveal latest research

Strawberry growers are over-watering their crops to the detriment of yields and fruit quality - meaning they are also wasting an increasingly scarce resource.

These are the main conclusions of an ongoing LINK and Defra-funded project being run by East Malling Research's (EMR's) Dr Mark Else.

The project, started last year, runs until 2012 and was one of the three studies explained to growers during a series of EMR farm tours at this year's Fruit Focus.

Else claimed that by scheduling irrigation to more accurately satisfy the crop's needs it was possible to substantially reduce water use by more than 70 per cent. In the strawberry sector alone, this was equivalent to the combined capacity of 174 Olympic-size swimming pools.

"The abstraction in strawberry growing areas where water is scarce is unsustainable," he said. "We're trying to devise practical solutions to this problem."

Growers learned about three approaches to irrigation scheduling that could help them conserve water to the benefit of crop yields and quality.

The methods included that being trialled by Else entailing the use of an Evaposensor - which measures plants' evaporation/transpiration - for determining plants' daily water use. A proportion of this usage, rather than all of it, is applied to the crop with the aim of improving berry yield, firmness, shelf life and flavour - tests so far show that the plants can perform better if slightly dehydrated.

The second approach was explained by water management specialist Peter White. He uses an EnviroSCAN, a sensing device, to monitor soil moisture levels at various depths within the soil profile in the crop. This information allows growers to match soil moisture to the perceived requirements of the crop with significant water savings.

"The way (many) growers irrigate their strawberries is pretty awful," he claimed. "(As a result) consumers say the fruit has poor shelf life and doesn't taste very good."

Dr Martin Wood of Earthcare Environmental demonstrated his closed-loop system, which uses echo sensors or probes below the plants to measure soil moisture. When a given moisture threshold is reached, the irrigation system is automatically switched on.

He explained that the water from each dripper extends about 40cm horizontally so it's logical to place sensors horizontally too, about 25cm deep. "We allow the soil to dry before irrigating, although that might need a bit of courage (on growers' part)," he said.

The tour's second stop was to hear about University of Leeds PhD student Nada Surbanovski's work on aquaporins. These are proteins in cell walls that conduct water and work like taps, controlling water flow into and out of the cells - depending on factors such as soil moisture content.

Using three drought-resistant wild strawberry species, Surbanovski is determining how aquaporins work and how to control them to the benefit of crop performance.

The study that was explained by Dr Jean Fitzgerald at the tour's final stop entails investigating the value of ground-inhabiting predators, notably beetles, for orchard pest control - and the best way of attracting them into orchards.

To do this she has used a young organic apple orchard in which different types of ground cover have been established. They comprise knapweed, chosen for its upright growth, ground-hugging white clover, an organic mulch and bare soil. Pitfall traps are being used to assess ground beetle numbers.

"The aim is to increase the number of beetles in the orchard and, as a result, improve the control of pests like apple leaf midge," said Fitzgerald. "This midge pupates in the ground so if we can encourage ground beetles into the orchard they will mop up the pupae (or larvae as they fall from the trees)."

She has found more beetles in the traps in the knapweed. This was sown in the tree rows but because it competes with the trees for nutrients and moisture, in practice it would be grown on orchard verges.

In another study Fitzgerald has used flowering plants like corn marigold and camomile to attract flying predators such as hoverflies into the orchard. She pointed out that many ground beetle species feed on the eggs and larvae of vine weevil - an increasing problem in strawberries and raspberries.

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