Beneficial effects of biochar application on lettuce (Lactuca sativa L.) growth, root morphological traits and physiological properties

Biochar application is widely used to improve plant growth by increasing soil fertility. This study aimed to assess the effect of biochar on lettuce growth, root morphological traits and physiological properties under greenhouse conditions. The study was performed in a greenhouse, using biochar additions of 1%, 2% and 3% in a pot experiment. The plant parameters assessed under greenhouse conditions were the germination rate, leaf length, leaf number, leaf width as well as fresh root weight, fresh shoot weight, dry root weight, dry shoot weight, and root morphological traits. Furthermore, chlorophyll content and relative water content were evaluated. Both biochar 2% and biochar 3% treatment ssignificantly improved lettuce growth (leaf length, leaf number, leaf width) compared with the control, while no significant differences were observed in the biochar 1% treatment. However, biochar 3% treatment significantly enhanced the root morphological traits such as total root length, the root surface area, the projected area and the root volume compared to the control. The total chlorophyll content and carotenoid content improved with increasing levels of biochar 3% treatment, which significantly increased by 43% and 51% compared with the control. The highest acid phosphomonoestrase activities were seen with the application of biochar 3%, which was 19% and 31% higher than that of the biochar 1% and control treatments, respectively. Moreover, a significant increase in soil enzyme activities (fluorescein diacetate hydrolase, acid and alkaline phosphomonoestrase) was observed with the biochar 2% and biochar 3% treatments compared to the control. This study indicated that biochar could promote lettuce growth and enhance soil enzyme activities.