Soil Properties And Environmental Assessment Of Agricultural Soil In Different Terraces Of Yangling Area

The physicochemical properties, heavy metal contents and enzyme activity of agriculture soils of different terraces in Yangling area were determined by field survey, sample collection and laboratory analysis to explore the possible effect of soil properties and evaluation methodology from the points of comprehensive fertility, biology and heavy metal pollution. The result showed that:1 In the same terraces soil of Yangling,soil electrical conductivity, total nitrogen, available nitrogen, available potassium, available phosphorus, organic matter content decreased with soil depth of soil, while the pH value increased gradually with increasing soil depth. For the different terraces soil, the organic matter, total nitrogen, available potassium in the second terraces are highest, while soil pH values increased with the decrease of the topograph, soil conductivity and available nitrogen and available phosphorus decreased with the terrain decreases.2 The contents of soil heavy metals in different terraces of the area were significantly different. It performance as that third and second terrace stayed at higher levels, while the first terrace lower. Different heavy metals showed different distribution in soil of different depths. Cu, Zn, As, Cr content decreased with soil depth, while Ni showed a slight increase with increasing soil depth, Pb is performance in the 20 ~ 40cm at the highest levels. Single factor, multiple factors, ecological risk assessment results show that contents of heavy metals in the soil in three terraces of Yangling were below the environmental standards. The soil was in slightly ecological harms.3 The activity of soil urease, alkaline phosphatase, catalase, invertase, microbial biomass C and N content, microbial respiration in different terraces were all expressed as the third terrace to the lowest, three terraces to the highest .For the same terrace, different depth of soil urease, alkaline phosphatase, catalase, invertase activity, microbial biomass C and N content, microbial respiration with soil depth is manifested in the increase of lower amplitude varied.4 Principal component analyses revealed that the 25 indicators in the determination could be divided into four main components. According to the order of the contribution rate, they were divided into heavy metal; soil enzyme activity, physical properties, nutrient targets; which were Zn content, catalase activity, silt, and nitrate have the greatest impact on the Yangling environmental quality.