[ASC-media] Sun shield reduces water needed to grow vegetables: southern NSW trial

joanne.finlay at dpi.nsw.gov.au joanne.finlay at dpi.nsw.gov.au
Mon Apr 30 00:35:54 CEST 2007

30 April 2007

Sun shield reduces water needed to grow vegetables: southern NSW trial

A new means of shielding broadacre vegetable crops from the sun could 
massively reduce the quantity of water required to grow vegetables in some 
of the driest parts of the Murray Darling Basin.

Preliminary trials by growers in Griffith, supported by the NSW Department 
of Primary Industries (DPI), indicate that a new Israeli technique using 
'screenhouses' could see water used for growing vegetables cut by more 
than a third.

An Israeli research trial, reported last year in the journal Irrigation 
Science, found 38 per cent less water was required for 'screenhouse' crops 
compared with crops grown in open fields.

Griffith vegetable growers, Tony and Frank Catazariti and John and Anthony 
Vitucci, are in their second year of producing melons and mini capsicums 
using a shadecloth structure that covers one hectare. The cloth protects 
what are essentially field-grown vegetable crops.

Several years of research by the cloth suppliers, Queensland 
based-Envirotech, was required to determine the best combination of colour 
and density of shade cloth on the roof to modify sunlight penetration, and 
on the sides to moderate wind speed.

DPI District Horticulturist, Mr Mark Hickey, says the Australian trial is 
supporting overseas findings that sunlight intensity, windspeed and 
evaporative losses from the plant and soil surface were all lower and 
provided a more favourable environment for plant growth.

In the first year melons were grown in the structure, and this year mini 
capsicums ? a high value crop not normally grown in southern NSW ? were 
successfully grown using the new system.

Mr Hickey said in the first year of operation there was a dramatic 
difference in amount of moisture extracted from the soil by melons grown 
inside and outside the 'screenhouse'.

Two different methods were used to determine soil moisture levels in the 
root zone of the crop, and studies of the root systems of the protected 
crops were undertaken.

Initial estimates from the growers are that 30 percent less water was used 
to grow the melons under the shade cloth, compared with outside 

"A crucial factor is an estimated 40 percent reduction in 'global 
radiation', which means that evapo-transpiration is reduced.

"This is a significant benefit in terms of reducing water use but makes 
water management crucial, as excess water can lead to root diseases such 
as pythium and phytopthora."

Mr Hickey said the shadecloth structure also creates a more conducive 
environment for pests, which means crops have to be carefully monitored to 
check for the spread of viruses.

Trials of the new system are to be extended in the next two years in a 
collaborative effort by NSW DPI and CSIRO Land and Water, under a new 
research project into water use efficiency in horticulture funded by the 
Cooperative Research Centre for Irrigation Futures (CRC IF).

Mr Hickey said further research needs to be undertaken into the impact of 
the new growing system on evapo-transpiration, through monitoring of daily 
changes in moisture levels, as well as on pests and diseases.

"One advantage of this system is that it does not overheat crops, as 
happens in greenhouses."

The Griffith growers believe the screenhouse is economically viable, but 
the cost benefit of the system for other growers still needs to be 
assessed. This will be examined as part of the CRC project.

As with vegetable growing regions in the Murray-Darling Basin, Israel's 
semi-arid and arid regions require irrigation to survive. Growers in 
Israel have limited access to freshwater and between1980 and 2002 and the 
amount of freshwater available for agriculture in that country fell by 
more than half.

MEDIA INQUIRIES: Joanne Finlay 6391 3171 or 0428 491813

Joanne Finlay
Science Communication Specialist
NSW Department of Primary Industries
Head Office
Locked Bag 21
Phone: 02 6391 3171
Fax: 02 6391 3749
Email: Joanne.finlay at dpi.nsw.gov.au
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