Silicon (Si), an abundant element in the Earth's crust, has the potential to play a crucial role in sustainable agriculture by enhancing crop production and stress resistance. Maintaining or increasing soil organic carbon (SOC) levels in agricultural soils is challenging due to conventional practices that deplete SOC, leading to soil degradation and diminished fertility.

This study aimed to evaluate the impact of silicon fertiliser on grain yield and post-harvest SOC of the spring wheat variety 'Scepter' across three locations—in Victoria, Australia, over the 2022 and 2023 growing seasons, in different cultivated areas, under rainfed conditions. The experimental design was a randomised complete block with four replicates for each foliar Silicon (FS) treated and control plots in 2022, and eight replicates for each FS, Soil Silicon amendments (SA) treated, and control plots in 2023. In 2022, wheat crop at three locations experienced different degrees of water logging stress at critical growth stages due to heavy and continuous rainfall.

FS-treated plots saw a higher though non-significant difference in mean grain yield compared to controls (4.91 t/ha) at Dookie trial site. The positive trend was observed in FS-treated plots at 5.43% (p-value= 0.051) greater than controls (3.98 t/ha) at Birchip cropping trial site in 2022. However, at Riverine Plains trial site we found a significantly higher yield of 29.77% (p<0.01) in FS-treated plots compared to controls (2.41 t/ha). In the year 2023, which was a normal cropping year in case of climate conditions, the comparison of grain yields between FS-treated or SA-treated plots showed statistically similar yields compared to control plots at Dookie (7.01 t/ha), Birchip (5.99 t/ha) and Riverine Plains (3.34 t/ha) trial sites.

Soil organic carbon levels in FS plots at Dookie trial site depicted a significant 12.24% increase (p<0.01) compared to the control plot in 2023. SA-treated plots at Dookie trial site in 2023 exhibited a significant 23.72% increase in SOC% (p<0.01). At Birchip cropping trial site, FS-treated plots demonstrated a significant 13.19% increase (p<0.01) in SOC measurable, and SA-treated plots had a significant 11.28% increase (p<0.05). The significant differences in grain yield between the two years of this study, concerned with waterlogging stress in 2022, highlight silicon's positive impact under stress conditions compared to non-stressed conditions.

Additionally, the enhancement of SOC indicates silicon's potential role in promoting soil health in short-term applications. These findings support the use of silicon fertilisers as a sustainable agricultural practice to mitigate soil degradation and enhance stress resilience.

However, the observed positive trend in SOC of this study could be attributed to the increase in particulate organic carbon most likely due to recent crop growth in the short-term. Hence, this came into consideration whether the observed increase in OC due to applied silicon fertiliser is a one-time event or a consistent trend of increasing OC levels.

Understanding the full picture requires further research to explore the long-term effects and broader applications of silicon across different conditions.

Keywords: Silicon Treatment, Spring Wheat, Sustainable Agriculture, Victoria