Waterlog woes could cut grower yields

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Cally DupeThe West Australian
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A Lake King property impacted by waterlogging due to rainfall.
Camera IconA Lake King property impacted by waterlogging due to rainfall. Credit: DAFWA

Graingrowers with flat country prone to waterlogging and salinity could face yield losses after the widespread summer rain.

Department of Agriculture and Food principal research officer Richard George advised growers to soil test at-risk paddocks and adjust cropping programs accordingly.

Dr George said about a million hectares of arable land in the grainbelt were vulnerable to increased salinity, waterlogging or both after the wet summer. Conditions this season could result in significant yield losses of up to 25 per cent in affected paddocks.

“Wet seasons are not uncommon,” he said. “If growers had waterlogged valleys in 2000 and 2006, they may encounter problems this year, such as getting bogged or poor plant growth,” he said.

“The water table has become very shallow, bringing salt up into the root zone due to evaporation. Unless there is sufficient autumn rainfall to flush the salt away, plant growth and yields could be considerably retarded by salinity.”

Dr George said soil testing would identify the electrical conductivity (EC) level, which would provide consultants and growers with a better understanding of the salinity threshold in the paddock.

“It is also important to remember that even if valley floors dry out over coming weeks, the soil profile is full of moisture and won’t take much to saturate again and become waterlogged,” he said.

Dr George warned if there was a dry finish to the season, crops could be subjected to a ‘double whammy’ salinity impact.

“If these conditions eventuate, crops will not only be hit by waterlogging, hindering seed germination and early plant growth, dry conditions will also facilitate the capillary movement of saline water from the water table to the soil surface, which could result in poorly developed root systems and various forms of crop toxicity,” he said.

He said landholders should have short-term tactical options and longer-term strategic solutions to areas prone to waterlogging.

“Growers need to consider the seasonal outlook and determine whether to sow a crop on susceptible land this season,” he said.

“If so, crops with greater salt tolerance should be considered, such as barley and canola.

“It will be important to retain as much stubble as possible, which can act as a mulch to help reduce the movement of saline water to the soil surface.”

Dr George said urged growers to reflect on the movement of water over paddocks in recent weeks and to integrate this knowledge into their long-term property management strategy.

“This year provides a good opportunity to develop a better understanding of how high rainfall affects growers’ soil resources, especially on slopes, and how water movement is influenced by different tillage systems,” he said.

“Then they can plan amelioration options to alleviate run-off to ensure continuity of flow of water across valleys so water is removed after three days, before more severe waterlogging and salinity issues arise.”

For more information visit agric.wa.gov.au and search for “water salinity”.

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