Field evaluation of the potential for CO2 emission prediction using humus parameters of fallow soils under tillage

A model field experiment was carried out over two consecutive growing seasons (2022 and 2023) in the tilled areas with low, medium, and high levels of soil organic matter (SOM) (experimental sites) and adjacent fallows (control sites) to evaluate the potential for predicting CO 2 emissions from humus parameters of the old-arable horizon of fallow light gray forest soil. The CO 2 emissions from the experimental sites exceeded those from the fallows by 3.2–3.4 times in the first year and by 2.6–3.3 times in the second year. The mean differences in CO 2 emissions between the experimental and control sites were 0.175, 0.214, and 0.225 g С-СО /(m 2 ×h) in case of low, medium, and high SOM levels, respectively. The content of Na 4 P 2 O 7 –NaOH-soluble carbon (Calk) decreased significantly at the sites with medium and high SOM levels, while the decline in total carbon (Ctot) was not significant, and boiling-water-soluble carbon (Cbw) increased. Among the studied parameters, Calk showed the greatest potential as an indicator of humus state in fallow soils for predictive modeling of CO 2 emissions during land use change.