Role of simulated acid rain on cations, phosphorus, and organic matter dynamics in Latosol

Acid rain is a serious environmental problem in the world and is of a particular concern in southern China where most of the soils are acidic. This study investigated the dynamics of cations, phosphorus (P), and soil organic matter (SOM) in the Latosol (acidic red soil) from south China under the influences of simulated acid rain (SAR). Laboratory experiments were performed by leaching the soil columns with SAR at pH levels ranging from 2.5 to 7.0 over a 21-day experimental period. Results show that about 34, 46, 20, and 77% of the original exchangeable soil Ca(+2), Mg(+2), K(+), and Na(+), respectively, were leached out by the SAR at pH 2.5 after 21 days. Two distinct patterns of the available phosphorus (AP) concentrations were observed: one at pH< or =3.5 and the other at pH > or = 4.0. At pH< or =3.5, concentrations of the AP increased from the beginning of the experiments to day 5, then decreased from day 5 to 15, and finally increased from day 15 to the end of the experiments. At pH > or = 4.0, concentrations of the AP increased consecutively from the beginning of the experiments to day 10 and decreased from day 10 to the end of the experiments. Such a finding is useful for agricultural practices since soil P is one of the most important macronutrients for plant growth. In general, SOM content decreased with time as the Latosol was leached by the SAR at all pH levels. A maximum concentration of soil fulvic acid was found after 15 days of the experiments due to the degradation of the SOM. A multiple regression analysis showed that a very strong relationship was obtained between the soil AP and the other three parameters (i.e., pH, SOM, and sorption P).