Sapropel or gyttja are the terms that relate to specific water body sediments containing a high level of organic matter formed from the remains of water biota mixed with mineral components. One of the most promising utilisation ways of sapropel is agriculture and forestry where this natural material can be used as soil amendment to enrich soil fertility, neutralise acidity, improve water capacity and reduce phytoavailablity of excess of metallic elements. The aim of this study was to perform plant germination and early seedling tests using various sapropel samples and to reveal response of plant development depending on the type of sapropel to be used as soil amendment. Pure natural sapropel and sapropel/sand substrate of such types as peaty, organic-sandy, cyanobacteria, green algae and carbonatic sapropel, derived from four lakes of eastern Latvia, were tested. Seeds of cucumber Cucumis sativus and tomato Solanum lycopersicum as dicotyledons and perennial rye-grass Lolium perenne as monocotyledon were chosen for the experiment. Seed germination and early seedling tests were performed in PHYTOTESTKIT plates. Seeds were germinated in thermostat at a temperature of 26 °C for 7 days but early seedling development was achieved after 23- 30 days (depending on plant species) under daylight conditions at a temperature of 20 °C. Developed radicles and hypocotyls were measured, shoots and roots were weighed. The obtained results showed a distinctive effect of applied sapropel type on the development of plants depending on species and substrate – substrate containing pure natural sapropel is effective for cucumber and perennial rye-grass, but not for tomato.