Effects of acid soils treated with lime and polyacrylamide on the growth and physiological characteristics of flue cured tobacco

In this study, the effect of acid soils treated with lime and polyacrylamide (PAM) on the growth and physiological characteristics of K326 fluecured tobacco under soil culture conditions was investigated. The results showed that the acid soil significantly inhibited the growth of fluecured tobacco. On the acid soil treated with lime and PAM, when the PAM content was low (0.1%), the biomass of flue cured tobacco was significantly enhanced. The photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) also increased and root system activity was enhanced but relative conductivity and malondialdehyde (MDA) content decreased. With the increase in PAM consumption, the fluecured tobacco grew more slowly. In acid soils, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase(CAT) of fluecured tobacco leaves and roots were at their lowest. After adding lime alone, the activities of the three enzymes increased and after adding lime with PAM, when the PAM content was low, the activity of the three enzymes declined, and with increased PAM content (0.2%), the enzyme activity started to rise again. In the acid soil treated with lime and PAM, the change of soil exchangeable hydrogen and exchangeable aluminum content was caused by the lime, but the influence of PAM was not significant. The influence of lime on the soil moisture content, water potential, specific gravity and porosity was not significant, but the influence of PAM on these factors was significant. The soil moisture content increased with a low PAM content (0.1%), but with an increase in PAM consumption, the soil specific gravity and porosity further increased, while the soil moisture contents gradually decreased and the soil water potential decreased significantly. It is conferred that the lime significantly reduced the acid soil exchangeable hydrogen and exchangeable aluminum contents, appropriately enhanced the soil porosity, increased the soil moisture content, and thus promoted the growth of flue cured tobacco. When the PAM was excessive, fluecured tobacco grew slowly, possibly because the excessive PAM caused the decrease in soil water potential and water absorption of flue cured tobacco became difficult.