ALTHOUGH many crops should bounce back physiologically from the wet in most areas across the east coast, there is a big issue in getting adequate nitrogen to crops through the crucial tillering and flag emergence period.
Many cereal crops are currently in the crucial growth stages from mid-tillering to flag emergence, and with farmers unable to apply fertiliser either on the ground or by plane, there is the risk the window of opportunity will close before urea can be applied.
Researchers differ slightly as to the stage when top-dressing nitrogen on crops will have a yield response, but it is generally regarded to be from flag emergence, potentially as far through as the booting stage.
Another issue farmers face is the prospect of nitrogen running straight off paddocks should the heavy rain forecast over the weekend saturate crops to the point of free water laying.
Birchip Cropping Group consultant Brooke White said now was the ideal time to top-dress urea, should conditions suit.
“It would be a good time now, but hopefully crops won’t lose too much yield potential due to nitrogen not being applied.
“We are hoping that mineralisation of nitrogen will occur in the soil when conditions begin to warm up, and that this effect will boost nitrogen levels a little.”
Southern Farming Systems chief executive Jon Midwood had a warning to farmers scurrying to apply urea prior to the weekend’s big front.
“Be very careful putting urea out when it is wet, if it is waterlogged, the nitrogen will just be run out of the paddocks,” Mr Midwood said.
“There are economic and environmental concerns with applying nitrogen under these conditions.
“It’s a real Catch 22, as the crops need the nitrogen now, but there is no point putting it on if the fertiliser is simply going to be washed away.”
Lee Menhenett, technical agronomist with Incitec Pivot (IPL), said even before the wet, IPL research had found many crops in Victoria, NSW and South Australia were potentially nitrogen deficient.
He said it would be delicate timing to get an economic response from nitrogen applications now.
“One of the worst things for volatilisation is to apply urea to a moist soil drying out, while it will just run off if the moisture profile is too full and it can’t penetrate the soil,” Mr Menhenett said.
“I would estimate the window for economic response to nitrogen is probably about three weeks, if crops are close to flag leaf emergence now.
“Should this rain eventuate, the best case scenario would be some good drying weather for a fortnight, which would allow farmers back on the paddock, followed by a light rain event of 5-10mm that would wash the nitrogen in, without causing further saturation.”
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