Effects of short-term exposure of simulated acid rain on the growth of Acacla nilotica

The response and measurable effects of simulated acid rain at different pH levels of 3.5, 4.5, 5.5, 6.5 and 7.0 on Acacia nilotica seedlings grown on black and red soils were investigated for six months. A set of 10 potted seedlings in each treatment was exposed to 15 min foliar spray of 125 ml simulated rain acidified with sulphuric and nitric acids at a ratio of 2:1. The simulated rain was sprayed in 10 spells from 45-70 days after planting. The study was conducted in the non-monsoon season to exclude ambient rain. Increasing acidity of simulated acid rain resulted in a general decrease in all growth characters of seedlings in both soils, namely, plant height, root length, leaf number, total dry matter accumulation, leaf dry weight, stem dry weight, root dry weight, leaf area, single leaf size, specific leaf area, leaf area index, leaf area ratio and crop growth rate. However, A. nilotica on red soil showed deleterious morphological and growth characters when exposed to simulated rain at pH 3.5 compared with those on black soil.