[Effects of biochar and EM application on growth and photosynthetic characteristics of Sesbania cannabina in saline-alkali soil of the Yellow River Delta, China].

We examined the effects of biochar and effective mircoorganisms (EM) application on growth and photosynthetic characteristics of Sesbania cannabina in the Yellow River Delta, by a pot experiment with different EM treatments (without EM addition, EM-; with EM addition, EM+) and a gradient of biochar treatments (0, B ₀ ; 0.5%, B ₁ ; 1.5%, B ₂ ; 3%, B ₃ ; biochar weight/soil weight). The growth parameters, photosynthetic light response curve and chlorophyll fluorescence characteristics of S. cannabina were measured. The results showed that the EM+B ₃ treatment had the best effect among all the treatments. Compared with the EM-B ₀ treatment, the EM+B ₃ treatment increased height, stem diameter, and total biomass by 69.5%, 90.0% and 141.1%, respectively. Biochar and EM significantly improved photosynthetic capacity. Compared with the EM-B ₀ treatment, the EM+B ₃ treatment significantly enhanced the maximum light response of net photosynthetic rate, transpiration rate, water use efficiency, and stomatal conductance by 93.8%, 35.1%, 43.4%, and 34.8%, respectively. Biochar and EM improved the parameters of chlorophyll fluorescence. Compared with the EM-B ₀ treatment, the EM+B ₃ treatment significantly increased the potential photochemical efficiency, the actual photochemical efficiency, the apparent electron transport rate and the non-photochemical quenching coefficient by 25.8%, 31.5%, 37.2%, and 56.8%, respectively. The parameters of growth, photosynthesis and chlorophyll fluorescence increased with the increasing biochar under EM+ treatments, whereas the B ₃ treatment had negative effect under EM- treatments. The co-addition of EM and 3% biochar (EM+B ₃ ) could improve the photosynthetic capacity and chlorophyll fluorescence characteristics of S. cannabina , broaden light ecological amplitude, boost the water retention and drought resistance property, and promote the growth of S. cannabina .