Changes In The Trace Element Content Of Soil In The Desert Region Of Northern Loess Plateau

Soil trace elements such as B, Cu, Zn, Mo, Fe, Co are essential elements for plant growth. Trace elements are often components enzymes, vitamins and growth hormones, thus directly participating in the metabolism process of plants. Crop requirements for trace elements are very small, however, they can be not lacking if the crop growth process is to be normal.. If the trace element content of the soil is low or if the trace elements are unavailable to plants, then crop production will be limited. It is important of study the content, distribution, speciation and transformation processes of trace elements in order correctly judge the soil's ability to supply trace elements to crops. The objective of this study was to investigate the trace element content, speciation, and distribution in a sandy soil. The study also investigated changes in soil trace element content under different land use and farmland management techniques. This study should help scientists to understand the soil micro-environment condition and the influence of the soil environment on the whole environment in the region. The results could help to prevent and control desertification and dust storms, enhance crop yield, and improve the living standard for local people.So, in order to combating wind erosion and sand storm, the paper conducted in sand region of northern jinbian county, combining the methods of investigation and sampling in the wild, and experiment and statistics in the room. We studied on the distribution and content of the trace elements in this region. And analyse the facters affected on its changes. The results are as follows:(1) Soil available trace element contents:The mean content of soil available B, Cu, Zn, Fe and Mn in the entire area in the 0-20cm surface layer (top soil) was: 0.421 mg.kg-1, 0.505 mg.kg-1, 0.582 mg.kg-1, 7.092 mg.kg-1 and 7.251mg.kg-1 respectively. Soil available B, Cu, Zn, Fe, and Mn ranged from 2.582 ~ 0.022 mg.kg-1, 1.194 ~0.158 mg.kg-1, 3.944 ~ 0.096 mg.kg-1, 26.080 ~ 2.400 mg.kg-1and 13.390 ~ 2.082 mg.kg-1. According to national standard classes, the content of Cu, Zn, Fe and Mn are suitable, but B is lower. So, it is import to think much of using fertilizer B in the future.(2) Distribution of soil available trace elements:The distribution soil available trace elements content in the 0-20cm surface layer of this region can be summarized in the following way. Soil available B, Cu, Zn and Mn increased from northwest to southeast, but soil available Fe increased from southeast to northwest. The reasons for the differences in the distribution of trace elements can be related to soil texture, soil parent material, soil pH and the soil wind erosion. In addition, soil trace element contents were generally highest at Hongdunjie, which is along the Wuding River and lowest at Gaojiagou, which is dry farm land.In terms of vertical distribution, available B, Cu, Zn, Fe and Mn contents was significantly higher in the 0-20cm layer surface soil compared to the 20-40cm and 40-60cm depths. Differences in the trace element content of the 20-40cm and 40-60cm layers were not significant. In contrast, the available B, Cu and Zn in the 20-40cm layer was lower than in the 40-60cm soil layer, but available Fe and Mn in 20-40cm soil layer was higher than in the 40-60cm..(3) Reasons for the observed changes in available soil trace element contents:The natural factors (intrinsic reason) which affect the soil trace element content include: soil properties, especially soil organic matter and soil pH, and long-term wind erosion. Human factors mainly include the establishment of a shelter forest, as well as other land utilization and farmland management measures which local farmers use to prevent and control wind erosion. These factors include protection measures to enhance production, prevent wind, such as crop rotation systems, keeping stubble over the winter, and fertilization. All of these affect soil characteristics and lead to changes in the effectiveness of soil trace elements. Therefore, the adjustment of farming according to soil characteristics and local conditions is the key to soil trace element management.