The Research Of Effects Of Simulated Acid Rain On The Carbon, Nitrogen And Phosphorus In Red Paddy Soil

Hunan province is one of the major rice producing areas in China, and also one of the main distribution area of acid rain. The strong acid rain impact on soil quality to reduce the quality of paddy soil, threat to national food security, studies on the impact on the quality of paddy soilunder acid rain are meanful. The study investigated impacts of simulated acid rain upon fire soil indicators, as pH, carbon, nitrogen, phosphorus and enzyme. The main results were as follow:1. With the decrease pH of acid rain, there were no significant change in soil pH. However, the content of soil organic matter (SOM), dissoluble organic carbon (DOC) and microbial biomass carbon (SMB-C). SMB-C contentdecreased significantly (P<0.05).2. With the decrease pH of Simulated acid rain, the content of total nitrogen (TN), mineralized nitrogen (MN) decreased, andthe activity of microbial biomass nitrogen (SMB-N) was inhibited. As the growth of the leaching time, SMB-N content changed significantly (P<0.05).3. There was very little changes on total phosphorus (TP) after the acid rain, and available phosphorus (AP) content changed significantly. During the first piord it declined, and then rose, and in a certain intensity vailable phosphorus content is the lowest. Soil acidification could help increasing the content of microbial biomass phosphorus (SMB-P) to some extent, but the high-strength acid rain gradually retrained the population and activities of soil microbes.4. Acid rain inhibited the activities of sucrase. The lower the pH of acid rain, more sever inhibition there was, at the pH 3.5, inhibition of protease activity obviously. Soil acidification could help increasing the content of acid phosphatase activity to some extent, but high-strength acid rain gradually retrained the population and activities of soil microbes.5. Soil basal respiration (SBR) increased gradually when pH is 5.5 or more, but decreased dramatically when pH<4.5. The decrease in the average well color density (AWCD) revealed that there was a negative effect of simulated acid rain on soil bacterial metabolic function. A principal component analysis showed that the major carbon sources used by the bacteria were carbohydrates and carboxylic acids.6. Correlation analysis suggested both different forms of carbon and enzyme activity showed large additive effect on the pH. Carbon conversion significantly affected the nitrogen transformation. Relation among the nitrogen and enzyme activity were also close.