Abstract/Summary

Humic substances (HS) constitute a primary component of soil organic matter (SOM) and play a crucial role in soil formation and fertility. However, comprehensive information regarding quantitative and qualitative changes in HS following biochar application to soil still needs to be improved. This research reports on the impact of biochar application at rates of 0, 10, and 20 t ha⁻¹ (B0, B10, B20), both with and without nitrogen fertilisation at varying levels (N0, N1, N2), on SOM and HS throughout the cropping seasons between 2014 and 2019. The findings reveal changes in SOM and HS due to biochar addition and fertilisation. Notably, the most substantial increase in soil organic carbon content was observed in B20N1 and B10N1 treatments, in stark contrast with the reference B0N0 treatment. A decrease in humification of SOM was noted across all treatments involving biochar, either alone or combined with different N fertilisation levels. An interesting positive change was observed in HS in B10N2 where an increase in humic acids and a decrease in fulvic acids enhanced HS stability and improved HS quality. These findings shed light on the intricate dynamics of SOM and HS in response to biochar application and nitrogen fertilisation over multiple vegetation seasons of crops on loamy Haplic Luvisol in Central Europe.