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Vegetation restoration and reconstruction the Loess Plateau ecological restoration and protection of the foundation. Vegetation can be adjusted through the litter, root exudates and improve the physical and chemical properties of the soil and the microbial environment, low molecular weight organic acids in the rhizosphere environment of soil remediation. Improve soil quality plays an important role. For low molecular weight organic acids on the study of the mechanism of the soil but also rare. Lou Soil sample soil exogenous added citric acid treatment of exogenous citric impact on the Lou soil nutrients, enzyme activity and microbial activity, the following major findings: 1 total soil nitrogen With the addition of citric acid concentration increased loss gradually reduce, and with the processing of the increase of the number of days, the total nitrogen content widening gap between the different processing; soil alkaline hydrolysis nitrogen, nitrate, and available nutrients such as citric acid concentration, treatment time increases gradually reduced; increased soil total phosphorus content in 30 days, 30 days after each treatment were little changed; available phosphorus content decreased significantly with the increase in processing time. Soil pH with added citric acid concentration increased higher; early each treatment the soil pH increased with increasing time, late pH gradually smooth; soil conductivity gradually reduced with the increase in concentration, time and small. 3 of soil organic carbon with increasing concentration of citric acid treatment gradually increases; With the increased processing time, a low concentration (CK, treatment 1, treatment 2) organic carbon content gradually decreased, the high concentration ( 3 for 4, treatment 5) organic carbon content gradually increased and then smooth; increase in soil carbon and nitrogen over the previous period, the late change significantly, but high concentrations of citric acid treatment with low concentrations of citric acid treatment between N ratio the gap gradually expanded; same period microbial biomass carbon increased with the treatment concentration increased; With the increase in processing time, a slight decrease in soil microbial biomass carbon, handling late changes. Soil catalase activity was increased with time as a whole; growth significantly decreased the urease activity over time; sucrase large changes, there is no obvious regularity; alkaline phosphatase activity with citric acid concentration increased increase. By principal component analysis, on the the 14 fertility parameters under different concentrations of exogenous citric role reclassified, to simplify, to identify the main factor and soil variation. The first principal component soil N, P, and organic matter to microorganisms the organic transition comprehensive measure, reflects the soil microbial carbon, nitrogen, phosphorus fixed, reserve; second principal component reflects the different concentrations of citric acid in the impact small differences in soil fertility status and soil fertility under 3 citrate concentration indicators of change.
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