Getting the best from irrigation

THE costs of water and power are impacting on obtainable returns after irrigating crops and pastures.

At a recent field day, east of Gympie, Pat Daley from Daley Water Systems at Clifton outlined to the farmers present how to get the best out of an irrigation system.

Adding on to an existing system to increase area could lead to considerably reducing the efficiency of irrigation, Mr Daley said.

"A system has to be able to cope with different situations," he said.

"There has to be enough give in the system to be able to apply what the plants need when they need it."

Under watering reduced production, while over watering was wasteful and expensive.

Under-watering could lead to loss of crop if the plants' peak demand, usually at flowering and fruiting, could not be met. That peak demand might be necessary for only a short period, but was essential and the system had to be designed to cope.

Little and often irrigation could lead to problems in so far as the root systems were not forced to go deeper looking for water.

"In particular, pastures then suffer if high temperatures or prolonged rain eventuate.

"Wet weather causes plant roots to die off (they are not needed) and there is often a hot period after the rain has ceased."

Irrigation should be started while soil was still wet to maintain the schedule because once it was behind plants, and therefore productivity, suffered and it was just about impossible to catch up on the schedule, Mr Daley said.

While experience was valuable, measuring the soil water profile (using gypsum blocks) gave a more accurate indication of what the plants needed.

"I have found experience more often than not gives less irrigation than is required," Mr Daley said.

"The soil profile should be kept as full as possible to train roots to go down deeper."

The introduction of fertigation presented different challenges, with strategic fertiliser applications possibly required during rainfall events.

The system should be able to increase or decrease fertilizer rate in proportion to water flow.

"Fertigation using Ezi-shift or a travelling gun should not be attempted," Mr Daley said.

It was important to keep up with an irrigation schedule.

"If the rain does not come, irrigation schedules are often so tight you do not catch up," he said.

"Production and future growth is suffering well before any signs of stress in the plants."

Topics:  electricity charges field days irrigation

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