Make use of every drop: Hills

Make use of every drop: Hills


Dairy
WATER WISE: Irrigation efficiency researcher James Hills said irrigators should be wary of the "green drought", where water is not put to use.

WATER WISE: Irrigation efficiency researcher James Hills said irrigators should be wary of the "green drought", where water is not put to use.

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WITH water prices lifting, it is important to make the most of each drop of water when irrigating, says irrigation efficiency researcher James Hills.

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WITH water prices lifting, it is important to make the most of each drop of water when irrigating, irrigation efficiency researcher James Hills says.

The Tas Institute of Agriculture research fellow was speaking at the DairySA Central Conference, held last month, and said there was increased competition in accessing the limited resource of water, with dairy one of the biggest users of irrigation.

He said users needed to find the enterprise that would provide the greatest ratio of dry matter per megalitre, while still suiting the overall operation.

"Achieving high forage yields is key to water use efficiency, but it has to be the right forage species for the system," he said.

On average, ryegrass returned 1.1 tonnes of dry matter to 1.2t for each ML, turnips 3-4t/ML and maize 4-5t/ML.

But beyond selecting the right crop, there were other factors that could remove yield limitations, including soil fertility and grazing management.

"The biggest issues are with irrigation scheduling and its impact on productivity," he said.

Dr Hills said key questions to ask when assessing irrigation scheduling were how much water was readily available to the plants, what was the rate of evapotranspiration and what could the irrigation system achieve.

He said it was possible to work out the "bucket" of the soil, by assessing how deep the root system went.

"This has a significant impact on scheduling," he said.

He said one of the biggest mistakes irrigators could make was not irrigating following rain, and allowing the available water in the "bucket" to dry out.

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This often meant the rest of the season was spent playing catch up.

"By understanding scheduling and not allowing it to dry out, we can grow a heap more grass," he said.

Dr Hills said this was particularly true in pastures, which had shorter root zones, whereas lucerne could be different.

Variable rate irrigation in pivot systems was another method to deal with a range of soil types and "buckets".

Dr Hills said by simply turning the irrigation off through roads and laneways, there could be water savings of up to 34 per cent.

"The big problem is to get an effective map to reflect the issues in the paddock," he said.

Dr Hills said this could be expensive and would take up to eight years to pay back, if just saving water, but if the VRI also improved productivity by as much as 1t a hectare, it would be paid back in three years.

"It is worth doing, if you get productivity gains," he said.

He also cautioned against bigger pivots, saying they had a higher run-off rate near the outside of the range.

"What is the use of putting it on, if it's not getting where it needs to be?" he said.

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