Effect of aqueous extract of biochar on germination and seedling growth of lettuce {lactuca sativa l.

This study was carried out to confirm the effect of aqueous biochar extract on seed germination and seedling growth of lettuce (Lactuca sativa L.). Biochar produced from orange peel (OP), residual wood (RW), and water treatment sludge (WS) at pyrolytic temperatures of 300 and 700'C were extracted with distilled water at final concentrations of 1 and 3%. The germination rate in the OP significantly delayed than in its biochar treatments and finally reached to 52 and 0% at 1 and 3% concentrations, respectively. Compared to the control containing only distilled water, the germination rate in all biochar treatment except for the WS biochar produced at 700°C were similar or promoted. The OP inhibited the radicle as well as the hypocotyls and the inhibitory effect increased with increasing the concentration of aqueous extract. Similar results have been shown in the RW and RW biochar treatments, but the difference between radical growths was not statistically significant. In cases of the WS and WS biochar treatments, there was no significant difference on pyrolytic temperatures of the biochar and concentration of the aqueous extract between hypocotyl and radicle. These results suggest that the biochar had no negative effect on the germination rate and seedling growth. Therefore, biochar could be used not only as a valuable soil amendment to increase soil health and crop growth, but also as a carbon sink to mitigate global warming.