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WA forecast for dry conditions

16 May 2018
Grower News

The Department of Primary Industries and Regional Development’s Statistical Seasonal Forecast indicates a less than 40 percent chance of exceeding median rainfall from May to July, based on a poor to good predictive skill level.

The forecast is consistent with the Bureau of Meteorology’s current outlook, which suggests a 30-45 percent chance of exceeding media rainfall for the same period, based on a mostly moderate to good skill level.

The department’s growing season forecast for May to October is also for a less than 40 percent chance of exceeding median rainfall in the Grainbelt, based on poor to good predictive skill. The forecast for drier than average conditions translates to a decile two to three rainfall range.

The Bureau’s temperature outlook is for warmer conditions, with a 60 to 70 percent chance of exceeding average day time maxima in the Grainbelt, based on moderate to good predictive skill. Its minimal outlook is for a 50 to 65 percent chance of above normal temperatures, based on poor to moderate skill.

Department research officer Meredith Guthrie said an analysis of the SSF shows that agribusinesses can have confidence in the department’s seasonal forecasts. “Since 2012, the SSF has correctly forecasted May to July rainfall in the northern region, and had success in five years out of six in the central region and four years out of six in the southern region.

“The model has proved to be particularly useful at the beginning of the season to inform growing season decisions – but it is important to revisit the SSF as the season progresses, in case the determining conditions change.”

The SSF is one of several of the department’s growing season tools that can be accessed for free via its website, including real time data from its network of more than 175 weather stations and Doppler radarssoil water and rainfall-to-date tools.

Most growers north of the South Coast have finished sowing canola and are starting to plant barley, where soil moisture is still adequate, before moving onto wheat.

Despite widespread summer rainfall, stored soil moisture levels are extremely low across most of the Grainbelt, except for parts of the South Coast near Esperance and Albany.

Department research officer David Ferris said Western Australian growers were adept at adjusting to seasonal conditions and would be considering a range of options in response to the dry May outlook. “The dry conditions may prompt growers to pull paddocks from their cropping programme or to consider planting alternative crops or varieties.”

Dr Ferris said with the below average seasonal rainfall forecast, growers should consider delaying top-up nitrogen applications until they are confident that the investment is going to reap a reward. “Department research has shown top-up nitrogen for canola in low and medium rainfall areas can be delayed until the start of flowering, about twelve weeks after sowing.

“Following a small starter nitrogen application at seeding, top-up nitrogen for barley and wheat should be delayed to the stem elongation stage. This delayed nitrogen does not impact on yield, while providing benefits to grain protein.”

Growers are advised to closely assess their yield potential, stored soil water levels and weather forecast when deciding whether or not to apply further nitrogen and how much.

For more weather information during the season, click here.

Source: Western Australia Department of Primary Industries and Regional Development