Effects of Simulated Acid Rain on Soil Acidification and Tobacco Growth in Fields

Southwest China proves one of the areas with the highest acid deposition load in the world, and acid precipitation might be harmful to the ecosystem of tobacco field. In this research, automatic simulated acid rain monitor was used to simulate three conditions in tobacco field, i.e. natural rainfall (CK, pH 6.3), ultra-pure water (T1, pH 6.8) and acid rain (T2, pH 3.5). The acidification and cation characteristics of soils, and the growth, biomass, nitrogen, phosphorus and potassium accumulation of tobacco were determined. The results showed as the followings. (1) Compared with CK and T1, the soil pH in T2 decreased significantly, and the difference of soil pH increased gradually with the time prolonging. T2 also observed the increase of exchangeable acid and aluminium ion, and the decrease of CEC and total salt base. (2) T2 significantly inhibited the growth and development of tobacco, and significantly reduced the plant height, stem girth, available leaf number and the length or width of tobacco leaves. The stem and leaf biomass of CK, and the root biomass of T1 exhibited the highest, respectively. (3) The lowest accumulation of nitrogen and potassium in roots both occurred in T2, while the highest nitrogen accumulation in stems and leaves also occurred in T2, yet the lowest in CK. The potassium accumulation in stems and leaves exhibited the highest in CK, and the lowest in T1. The phosphorus accumulation performed no significant difference in different parts of tobacco, yet the lowest in T2. These findings indicate that acid rain with pH 3.5 might lead to soil acidification and significantly inhibit the growth and development of tobacco, whereas establishing control strategies is required.