Concerns about manganese (Mn) deficiency in lupins have increased with some believing the Jurien variety is more susceptible.
Most of these concerns can be traced back to poor establishment from plantings a couple of years ago and the incidence of split seed in harvested crops – a classic symptom of Mn deficiency.
Some granular Mn fertilisers such as Big Phos Manganese are very effective at supplying Mn to crops.
However, there could be deficiencies where Mn has not been applied, or where the fertiliser used has not done the job.
So, do we apply a foliar spray?
At the recommended rate (1 kg Mn/ha), the cost is around $20/ha - not cheap!
Makes sense then, to work out whether it’s actually needed.
Fortunately, the lupins can be easily tested, and the stem test at flowering (ideally when the primaries are flowering) has been shown to be the most reliable test.
Sampling is done by collecting whole plants, cutting off the roots, and stripping off the branches and leaves so only the main stem remaining. 20-30 stems per sample is recommended.
It only costs $21.25 per sample to get the Mn analysed – a lot cheaper than the cost of an foliar spray that may or may not be needed.
It’s worth the test.
Jurien lupins near Brookton, August 2020. Stem tested: 40 mg/kg Mn = adequate manganese