THE most important aspect of plant nutrition is having a plan in place, according to International Plant Nutrition Institute regional director Rob Norton.
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Dr Norton was one of the guest speakers at a recent GRDC workshop on nitrogen cycling and trace element management held at Murray Bridge.
“Hope is not a strategy,” he said.
Dr Norton said there were a number of determinants to safe nitrogen application at seeding, including row spacings, soil mixing, crop/seed type and size, soil moisture, the type of fertiliser and the formulation.
He recommended graingrowers visit the Seed Damage Calculator website – seed-damage-calculator.herokuapp.com – and use the tool as an aid in selecting the maximum safe fertiliser rate that can be applied with seed for various crops.
Dr Norton said the peak demand for nitrogen was from tillering to ear emergence, when crops can use up to four kilograms a hectare a day.
There were a number of tools farmers could use during the season to see if more N was required, including using N-rich strips, plant testing, shoot cuts or just going out to the paddock and looking.
“With N deficiency, the oldest leaves will be yellow,” he said.
Dr Norton said N-rich monitoring strips could be a particularly valuable tool.
“With a N-rich strip you’re just comparing a part of the paddock that has more N applied, to the rest of the paddock,” he said.
“It’s a very useful tool to monitor your N status.
“The main benefit of using a N-rich strip is that you know when not to apply any more N, because there won’t be any difference in the plots.”
Another guest speaker at the workshop was University of Adelaide crop nutrition expert Glenn McDonald, who said seed phosphorus concentration could vary considerably.
“With seed with high grain P, emergence is better, the establishment percentage is higher, early growth is better and grain yield is higher,” he said.
Dr McDonald said varieties with longer root systems were able to take up more P.
Time of sowing also had an effect on how much P was needed. “With early sowing, the P requirement is reduced,” he said.
“If you’re sowing in April, it’s still quite warm and the roots can grow more vigorously and they can explore the soil for P more freely.”
University of Adelaide research scientist Sean Mason also spoke at the event, and said soil sampling at depth for potassium and sulphur was required for accurate soil test results.
- Details: twitter @ANZIPNI and @AuCropNutrition
