The Effects of Biochar Pyrolyzed at Varying Temperatures and Different Water Types on the Properties of Lettuce and Soil

Although irrigation with recycled wastewater (RWW) is a remarkable approach in terms of ensuring the sustainability of fresh water (FW), heavy metals (HM) contained in RWW cause soil pollution and accumulation in the plant. Biochar can reduce these risks that regulate the mobility of HM in the soil and bioavailability in the plant, but this may differ depending on the varying pyrolysis temperatures of the biochar. In this study, the HM pollution of the soil and mineral content and physiological properties of the lettuce were investigated in irrigation with different water types of lettuce grown in soil applied with biochar pyrolyzed at varying temperature. The results showed that due to differing characteristics of biochars pyrolyzed at varying temperatures, biochars pyrolyzed at high temperatures increased EC and pH of the soil, P, and electrolyte leakage contents of lettuce compared to biochars pyrolyzed at low temperatures but decreased organic matter; TN; exchangeable cation; and Fe, Cu, Mn, and Zn contents of the soil and chlorophyll, leaf relative water, stomatal conductance and mineral contents, and plant weight of lettuce, while biochar excluded Na and Zn uptake of lettuce. Contamination factor, enrichment factor, and pollution load index revealed that especially Ni and partially Mn and Cu may pose a risk in terms of HM pollution and that irrigation with RWW and biochars pyrolyzed at low temperatures may increase the HM pollution size. It has been found that FW+RWW can be used safely in irrigation to improve the mineral content and yield of lettuce, and it can be suggested that biochars pyrolyzed at high temperatures (> 400 & DEG;C) should be used to reduce pollution of HM.