The addition of organic materials to the soil is important due to the sustainability of soil resources and their positive contribution to soil properties. Many materials that are added to the soil as a source of organic matter have direct positive effects, such as storing and storing carbon in the soil, as well as improving the physical, chemical and biological properties of the soil. Leonardite is one of the most preferred organic soil conditioner, which is rich in humic acid and formed by oxidizing organic materials without being affected by carbonization processes. Due to having high humic acid and carbon content, it has an important place in terms of soil improvement and vegetative production. This study was carried out to determine the short-term effects of leonardite obtained from two different sources ((Kayseri-Develi (DL) and Çanakkale-Yenice (YL)) on some properties of the soil with sandy loam (SL). For this purpose, each leonardite type was mixed with sandy loam (SL) soil at the rate of five different doses (4%, 8%, 12%, 16%, 20%) and they were incubated for three months. Soil organic matter (OM), soil reaction (pH), electrical conductivity (EC), lime content (CaCO3), bulk density (dB), saturated hydraulic conductivity (Ks), aggregate stability (AS) and total porosity (P) of mixtures were determined at the end of the incubation period to investigate the effects of leonardite. Leonardite applications increased EC (236%), OM (213%), AS (50%) and P (11%) while decreased dB (10%) compared to control (p≤0.05). However, changes in other parameters (pH, CaCO3, Ks) were not found significant statistically (p≥ 0.05). In general, it was determined that the effect of the leonardite type on the parameters investigated was not significant (p≥ 0.05).