Identification of most susceptible soil parameters for Latosol under simulated acid rain stress using principal component analysis

Purpose Acid rain is a problem of increasing agricultural, environmental, and ecological concerns worldwide. In recent years, coupled studies have been conducted to evaluate impacts of simulated acid rain (SAR) on Latosol in China. However, no efforts have been devoted to investigating which soil parameters are most sensitive to the influences of SAR. In this study, we addressed the issue using the principal component analysis (PCA) and principal factor analysis (PFA) techniques. Materials and methods A plastic cylinder with a 10-cm inner diameter was used to contain a 20-cm-long Latosol (acidic red soil) column. A total of 24 column spray treatments, namely 6 pH levels (i.e., 2.5, 3.0, 4.0, 4.5, 5.0, and 7.0) × 4 spray periods (i.e., 5, 10, 15, and 21 days) with triplicates, were carried out in this study. The SAR solution was slowly sprayed at a rate of 6 cm³ min⁻¹ to the top of the column every 24 h. The effluent and soil samples from the columns were collected and analyzed for soil quality parameter contents. These parameters were then analyzed by the PCA and PFA techniques. Results and discussion Changes in Ca²⁺ content in the Latosol due to the influences of SAR did not have discernable impacts on soil parameters. In contrast, Mg⁺² had fairly good positive correlations with Fe³⁺ (0.642) and negative correlation with humic acid (−0.644); K⁺ had good positive correlations with Mn²⁺ (0.724) and negative correlation with Fe³⁺ (−0.703); Fe³⁺ had good negative correlations with [graphic removed] (−0.755); Na⁺ had fairly good positive correlations with Cu²⁺ (0.656); Cu²⁺ had fairly good positive correlations with humic acid (0.638) and good negative correlations with phosphatase (−0.766); Zn²⁺ had good positive correlations with [graphic removed] (0.722); and OM had fairly good negative correlations with [graphic removed] (−0.696). Soil cations (i.e., Mg²⁺, K⁺, Na⁺, Cu²⁺, and Zn²⁺) and enzymes (i.e., peroxidase, urease, and amylase) were positively influenced by the SAR, while the most susceptible soil parameters under the SAR stress were in the following order: Mg²⁺ (91%) > Na⁺ (89.61%) > urease (89.6%) > amylase (89%) > Cu²⁺ (85.2%). Conclusions Impacts of the SAR on soil cations (i.e., Mg²⁺, K⁺, Na⁺, Cu²⁺, and Zn²⁺) and enzymes (i.e., peroxidase, urease, and amylase) were larger than those of OM and [graphic removed] in the Latosol. The most susceptible soil parameters under the influences of the SAR were in the following order: Mg²⁺ > Na⁺ > urease > amylase > Cu²⁺.