Citrus irrigation can be fine-tuned

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Drip irrigation has been questioned for its power to deliver sufficient water to citrus in hot climates but some growers have found it can be managed with excellent results.

Among them is Greg Hutchinson of Red Cliffs, who has reduced applications to 7 megalitres/hectare/year in a region where applications of 10 megalitres/hectare/year are common.

He hastens to add that not all situations are the same and what may work in one location may not work in another, but the figure shows that efficiency can be driven to a point where there is no further room to move.

What he has been able to achieve with his oranges also answers critics who say high-water-using crops should not be encouraged.

“Apart from water use efficiency, the total value of production than can be driven by water and other inputs has to be taken into consideration,” he said.

He has 6 hectares of oranges and 70 hectares of winegrapes and with low grape prices much better returns in recent years have come from the citrus.

Management of the 20 year old trees, all navels, is going to be made easier with infrastructure improvements by Lower Murray Water, providing more frequent access to water during winter. They were planted by Greg on what was an old soldier settler block, at a time when water authorities preferred sprinklers to drip.

Although there were no natural hard soil layers the soil had been compacted by vineyard traffic so was ripped and leveled before installing the sprinkler system and planting the trees.

Replacement of the sprinklers with a drip system a few years later involved two lines per row, able to deliver 1.25mm/hour. Patterns of irrigation vary from once a week for up to 15 hours to every two to three days in summer for up to 8 hours.

There is not a standard schedule, however, and this may be the reason for getting the yearly use down to such a low level. In addition to crop factors which are highest in winter and evaporation which is highest in summer, decisions are influenced by stage of development (e.g. flowering is a critical period), crop load and visual observations which are made each morning.

“I believe I have to manage the citrus personally and I like to keep a track of what the trees look like,” Greg said. “There may be signs of stress in the appearance and feel of leaves, there may be a flower load issue, or an indication from the size and development of fruit.”

In addition to the indicators from personal observations, professional services are employed for pest and disease monitoring and tests for nutrient status. Weather information is important, too, with a strategy to wet the soil in advance of heat waves.

Irrigation through drip has a further role as a vehicle for nutrient requirements.

Nutrient management, like irrigation, is influenced by more than one factor. For example, applications are not automatically made in prescription form to meet deficiencies indicated from leaf analyses. They can be held off if there is a small crop load and the chance of over-size fruit, or adjusted to suit growth and ripening of a normal crop.

Irrigation and fertigation focus on the root zone and it appears that good science and keen observations ensure optimum use of inputs.

Caption: Greg Hutchinson

Citation

Land & Water Australia. 2010. Citrus irrigation can be fine-tuned. [Online] (Updated November 29th, 2010)
Available at: http://lwa.gov.au/node/3797 [Accessed Thursday 1st of March 2012 07:28:53 AM ].