Response of Soil Microbial Population and Activity to Sunn Hemp Cover Crop, Combined Nano Zinc and Copper and Nitrogen Fertiliser Application After Canola Cultivation

Agricultural soil health and quality centre around the ability of the soil to cycle nutrients to growing crops. However, soil biological properties focusing on microorganisms and their contribution to soil health are also important. This study was established at Syferkuil and Ofcolaco to determine the effect of cover crop, combined nano Zn and Cu, and nitrogen fertiliser on soil biological properties. Sunn hemp was planted, slashed, and incorporated into the soil, followed by winter canola in a split split-plot design with sixteen treatments. Key factors analysed after harvest included bacterial and fungal populations, active carbon, microbial activity measured by Fluorescein Diacetate (FDA), organic matter, urease, and pH. Statistical analysis was conducted using JASP 0.19.3. Cover crop, nano Zn and Cu, and nitrogen fertiliser enhanced bacterial populations, active carbon, urease, organic matter, and pH at Syferkuil, most particularly in 2023, while 2024 showed minor improvements. Ofcolaco showed improvements in fungal populations, organic matter and urease in 2023, whereas 2024 exhibited marginal changes. Nitrogen fertilisation increased POxC, ranging from 10% to 22% and urease at 31% to 111% in both locations, although this varied across application rates. Treatment interactions showed improvements in some of the measured parameters but varied across seasons and locations. In conclusion, sunn hemp cover crop, combined nano zinc and copper and nitrogen fertiliser have the potential to enhance soil microbial activity through the application of 60 and 120 kgN ha−1, thus reducing heavy inputs of synthetic fertilisers in canola production.