Biochar changes in soil based on quantitative and qualitative humus compounds parameters

Due to the indisputable significance of humus in many biochemical processes as well as its increasing deficit particularly in light soils, alternative sources of substrates for the reproduction of this constituent should be sought. The aim of this study was to evaluate the effect of the addition of wheat straw and wheat straw biochar (in four rates) on quantitative and qualitative humus parameters. The following properties were determined in soil: pH, organic carbon, total nitrogen, humic and fulvic acids, carbon in the extract, non-hydrolysing carbon and spectrophotometric indexes for solution of humic acids including A2/6, A2/4, A4/6. After applying 1% and 2% additions of biochar to the soil, the Corg soil content significantly increased compared to the same doses of thermally unconverted straw. After 254 days of incubation, the addition of biochar to soil at higher doses, decreased the share of humic acid carbon (CHA, CFA) in the Corg content compared to treatments without organic additions and WS treatment. The nonhydrolysing carbon soil content was significantly increased by treatments with 1% and 2% additions of WSB, which indicates greater stabilisation of humus compounds and, at the same time, lower CO2 emission. Soil humic acids amended by treatment with biochar, especially at 1% and 2% doses, were characterised by lower A2/6 and A2/4 ratios. Recognition of changes that may occur in the quantitative and qualitative composition of soil humus after the application of biochar may in the future be helpful information for determining appropriate biochar dose