Are trends in silicon uptake a reason for concern?

Silicon (Si) is recognised as a beneficial nutrient for successful sugarcane growth. Silicon deficiency typically occurs in light-textured soils. Increases in cane yield ranging from 16 to 45% have been observed in field trials with sub-optimal levels of plant available Si. There has been a noticeable increase in crops exhibiting Si-like deficiency symptoms. Results of recent industry wide surveys identified the Si content of third leaf tissue samples for more than 50% of crops sampled across the Far Northern region and almost 80% of crops sampled from Tully, were below the established industry target.

While this is expected for crops growing in soils with sub-optimal to marginal levels of plant available Si, or where growers failed to apply the recommended silicate amendment, it is also being observed in crops where soil assays indicate cane yield responsiveness to silica application is either unexpected or unlikely, meaning Si is not required. The project will investigate if trends in Si uptake are impacting crop performance, identify how various soil chemical properties may influence Si availability and if changes are required to soil and/or plant tissue assay critical values to ensure adequate Si nutrition.

The project aims to address recent findings of widespread poor Si uptake in sugarcane crops by:

• reviewing previous Si soil-crop response research conducted in Australia and internationally,
• re-examining existing soil and plant tissue datasets,
• collecting additional datasets representing additional soil types, specific soil properties and a range of varieties over two consecutive seasons,
• confirming if symptoms being observed and reported in all crops represent Si deficiency,
• and establishing intensively monitored field sites representing a range of soils, districts and varieties to support the re-interpretation of soil assay critical values and suitability of the Si leaf tissue target value in identifying poor Si uptake.
Continuation of the project into phase two (subject to require further discussions) may include:
• confirming refinements to Si soil and/or plant tissue assay critical values and associated interpretation guidelines,
• determining how various soil chemical properties influence Si availability,
• better understanding the impact of poor Si uptake on crop performance, productivity and profitability,
• validating proposed changes to the SIX EASY STEPS interpretation guidelines (for Si),
• and identifying future research priorities (for example evaluating practices/products to better manage Si nutrition in sugarcane production systems).