The Effect of Chlorella vulgaris (Chlorellales: Chlorellaceae) on the Fertility of Sandy Soils and on the Composition of Soil Leachates

The aim of the manuscript was to verify the hypothesis whether the algal biomass of Chlorella vulgaris added as a fertilizer affects the properties of a sandy soil and the leachates from that soil. A pot experiment was conducted using sandy soil, which was enriched with a suspension of live Chlorella vulgaris cells. The concentrations of total nitrogen (N_total), ammonium nitrogen, nitrate nitrogen, total phosphorus (P_total), phosphate phosphorus, potassium, sulphates, turbidity, pH and electrolytic conductivity (EC) were determined in the leachates from soil. Soil samples from each pot were analysed for N_total, P_total, P_available, K_available, calcium (Ca), organic carbon (C_org.) and pH. Soil fertilized with suspended biomass of Chlorella vulgaris was enriched with nutrients, mainly nitrogen, phosphorus and calcium. The use of algae has also helped reduce nutrient losses in the soil. There was an increase in the concentration of SO₄²⁻ ions in the tested leachates, which could pose a potential threat to the environment. Conducted studies confirm the hypothesis that Chlorella vulgaris added to sandy soil as a suspension of living cells affects the fertilizing properties of the soil and the composition of leachates from the fertilized soil. Soil fertilized with Chlorella vulgaris biomass is more resistant to nutrient leaching. An important conclusion of the study is that the composition of soil leachates needs to be monitored when testing and applying this type of fertilizer, due to the risk of sulphates entering into the groundwater.