Effects of effective microorganisms biochar-based fertilizer on photosynthetic characteristics and chlorophyll content of flue-cured tobacco under water-saving irrigation strategies

Effective microorganism biochar-based fertilizer (EMBF) can improve the physiological properties of tobacco (Nicotiana tabacum L.) In this study, the irrigation and EMBF rates were applied as factors that influence the photosynthetic characteristics and chlorophyll content of tobacco. The experiment involved 12 treatments: CK1-CK3, T1 -T3, T4-T6, and T7-T9; these four groups represented 0, 100, 300, and 600 g EMBF pot(-1), respectively. Each group was irrigated at rates of 40, 80, and 120 L pot(-1). When comparing with the control treatment CK, results showed that net photosynthetic rate (P.), stomatal conductance (g(s)), intercellular CO2 concentration (C), transpiration rate (T), and soil plant analysis development (SPAD) increased by 8.21%-107.03%, 18.78%-118.27%, 18.78%-118.27%, 7.24%404.15%, and 3.47%69.09%, respectively, after EMBF application. The P-n, g(s), and T-r at the growth and maturity stages were highly significant (P < 0.01) and positively correlated with EMBF application. The P-n, g(s), and T-r were significant (P < 0.05) and positively correlated with irrigation, and C-i was less affected by irrigation (P> 0.05). The SPAD value of flue-cured tobacco at three growing stages was highly significant (P < 0.01) and positively correlated with the irrigation and fertilization rates. The SPAD values at the growth and maturity stages were higher than those at the rooting stage by 46.73%-79.2% and 2.21%46.17%, respectively. Furthermore, the 80 L pot(-1) irrigation rate combined with 300 g EMBF pot(-1) is the best water and fertilizer combination. The results of this study might provide theoretical and practical guidance for growing flue-cured tobacco in production areas.