The decrease in application of organic fertilizers into arable soils in Slovakia observed for the past twenty-five years has caused degradation of their physical, chemical and biological parameters. In order to solve this problem, Slovak farmers often add to soil such carbon-rich substances which either pose a risk of increasing the heavy metal content of soil, or whose purchase and use are economically demanding. Meanwhile, sawdust is a cheap and available carbon-rich material. Therefore, the objective of a two-year pot experiment was to determine the impact of sawdust used alone or with added inorganic nitrogen on the parameters of sugar beet yield as well as on some soil parameters. The results proved that the separate application of sawdust in autumn in doses of 3.4 t ha-1 and 6.8 t ha-1 caused the retardation of the growth of sugar beet and the decrease of the total chlorophyll content in leaves during the first 80 days of plant growth and development. This application did not have the significant impact on the root yield, but it increased the sugar content of sugar beet roots. The roots contained less α-amino nitrogen and more potassium. The number of nitrogen-fixing bacteria of genus Azotobacter chroococcum (AzCh) and the quantity of organic carbon in soil increased. The addition of mineral nitrogen fertilizer in a dose of 60 kg ha-1 into sawdust before sugar beet sowing in spring lowered or even eliminated the negative impact of sawdust itself on the beet growth and the content of total chlorophyll. It also increased the root yield. This addition had positive impact on the number of bacteria of the genus AzCh and the quantity of organic carbon in soil.

25.3.2020