Studies On Biogeochemical Characteristics And Environmental Influence Of Main Microelements In Farmlands Of Oasis

This paper takes Ganzhou district and Linze county of Gansu province as studied area, and analyzed the total and available contents of microelements (Cu, Zn, Fe, Mn, Ni, Co), soil physical and chemical properties, and their relationship between each others. The changes of spatial variability and pattern of available microelements are studied by using Geostatistics combined with GIS. The conclusions are summarized as follows:(1) The soil of studied area was alkali soil, in which the organic content was moderate- high, and available phosphorus content was moderate, but the ability of keeping fertility of soil was relatively weak. The content of carbonate was higher in the soil.(2) Compared with the average contents of microelements in the national soil, the contents of total Zn, Fe, Mn were lower in this area, but there were higher contents of Cu, Ni, Co. The contents of available Cu, Zn increased than in 1986, but the contents of available Fe, Mn decreased, and the contents of available Mn decreased drastically. Except several sampling points, major sampling points were not lack of the available Cu, Zn, Fe and Mn, whose contents were all higher than the critical contents which the crops grow need. After grading contents, the available Cu was rich-extremely rich; the available Zn and Fe were moderate-rich; the available Mn was lack-moderate; and the content of available Co distributed relatively even in different grades. The available rates of six microelements in the soil were in the order of Cu>Zn>Ni> Mn>Co>Fe.(3) Regression analysis showed that available Cu content was mainly affected by contents of organic and carbonate; available Zn content was mainly affected by organic content and available phosphorus content; available Fe content was mainly affected by available phosphorus content; available Mn content was mainly affected by pH value and organic content; available Ni content was mainly affected by organic content and cation exchangeable capacity; available Co content was mainly affected by available phosphorus content.(4) The available contents of Cu, Zn, Fe, Mn, Ni, Co in the study area showed spatial autocorrelation in the quite big spatial scope. But the spatial autocorrelation of available Mn, Zn contents were quite weak. The available Cu, Fe, Ni, Co contents had obvious spatial autocorrelation, and the spatial autocorrelation of available Ni was intense. The available contents of six microelements were low in the north of studied area which near the Heli and Longshou mountains, but higher in the farmland soil which near the Zhangye urban and Linze county than other areas.