A SIMPLE check on fertiliser rates may be the difference between delayed or reduced crop emergence and achieving target plant populations this season.

Incitec Pivot Fertilisers technical agronomist broadacre, Jim Laycock, said growers and their advisers should calculate safe rates of fertiliser with the seed before sowing, or separate seed and fertiliser, particularly for canola.

Canola is very susceptible to emergence problems if too much fertiliser is applied in the row with the seed. This tray shows the difference between wheat and canola emergence with 25 kg/ha of urea applied in the seed row.

“Canola is notorious for its sensitivity to fertiliser in the seed bed and can suffer damage ranging from reduced vigour to complete crop failure,” he said.

He said crops varied in their tolerance to fertilisers, with oats, barley and wheat being more tolerant than lupins and chickpeas, while canola was the most sensitive.

Mr Laycock said the damage to the seed could be caused by high levels of ammonia or from fertilisers drying out the soil around the seed.

He said growers were more likely to see issues where there was low soil moisture and on sandier soil types rather than heavier clay soils.

“Fertiliser type plays a role, with urea more likely to cause damage than DAP, and DAP more likely to cause damage than MAP or Granulock fertilisers,” he said.

“Even superphosphate has been seen to have a toxicity effect on sensitive crops like canola and lupins when it is used at high rates with the seed.”

Mr Laycock said the solution for growers and their advisers was to calculate the seed bed utilisation (SBU) percentage and be guided by safe seed rate guidelines.

“The SBU percentage is a risk analysis tool that can be used to determine the potential for emergence damage,” he said.

“It is a measure of how concentrated the fertiliser band is, based on the width of the seed spread in the furrow and the row spacing.

Jim Laycock

“Problems often arise when growers change to a wide row spacing and keep using their usual fertiliser rate, because the concentration with the seed is higher.”

Mr Laycock said once the SBU percentage was known, growers and their advisers could look up safe rates by crop type, soil type, soil moisture status and the intended fertiliser.

Because damage is so common in canola, he suggested growers to run a test strip comparing no fertiliser in the seed row with the rest of the paddock.

“This will show whether your usual fertiliser rates with the seed may actually be resulting in reduced vigour and lower plant populations,” he said.

Mr Laycock encouraged growers to consider application systems that separated seed and fertiliser when making machinery upgrades.

“There are some excellent options available to separate seed and fertilisers at sowing, such as double row systems, which give growers greater flexibility with fertiliser applications,” he said.

Source: Incitec Pivot