Biochar and vermicompost are among the important organic amendments used to improve soil quality and fertility; however, soil responses to their combined application may depend on the application rate of each amendment. The present study aimed to investigate the effects of sole and combined applications of biochar and vermicompost on selected chemical properties related to soil fertility under soil column conditions. The experiment was conducted as a factorial experiment based on a completely randomized design with four levels of biochar, including B0, B1, B2, and B3, equivalent to 0, 2, 4, and 6% by weight, and three levels of vermicompost, including V0, V1, and V2, equivalent to 0, 2, and 4% by weight relative to the soil, with three replications. For this purpose, polyethylene columns with a diameter of 10 cm and a height of 35 cm were prepared, and the soil was placed in the columns to a height of 30 cm. Following treatment application, soil pH, electrical conductivity (EC), available phosphorus and potassium, and total nitrogen were measured. Analysis of variance showed that the effects of biochar, vermicompost, and their interaction were significant for all measured properties. Increasing the biochar rate from 0 to 6% increased soil pH, EC, available phosphorus, available potassium, and total nitrogen. Similarly, increasing vermicompost generally increased the values of these properties, although the magnitude of the response depended on the treatment level. The highest available phosphorus (136.4 mg kg⁻¹), available potassium (935.3 mg kg⁻¹), and total nitrogen (2.45%) were observed under the combined application of the highest levels of biochar and vermicompost (B3V2). The highest pH (8.2) was recorded in the B3V0 treatment, while the highest EC (3.4 dS m⁻¹) was observed in the B3V2 treatment. Overall, the results indicated that the combined application of biochar and vermicompost, particularly at higher application rates, had considerable potential to improve the chemical status and fertility of the soil. However, the simultaneous increase in the application rates of these amendments was also associated with an increase in soil EC.