Fig. 2
Effect of foliar spray application of pine wood:clay:sand (PCS-BC; 70:15:15) and wheat straw:bird manure (WB-BC; 50:50) biochar extract, at different dilution rates, on the lettuce plant growth parameters. a Fresh biomass; b number of leaves; c chlorophyll (Chl) a; d Chl b; and e total Chl; f carotenoids and g anthocyanins; and h quantum yield of photosystem II (Fv/Fm). Different levels of chemical fertilizer (CF) were included to correspond each biochar extract treatment. A treatment consisting of only deionized water (DW) foliar spray was also included for comparison. Columns (means ± SE; n = 4) labeled by different lowercase letters are significantly (p < 0.05) different with each other