Study On Distributing Characters Of Manganese In Main Soil Profiles In Chongqing

Manganese is one of elements whose chemical valence is easily changeable. Manganese in soil is not only the offspring of soil forming process, but also one of the important signs of soil forming process. Euviation and illuviation of manganese in soil can make soil profile take on different configuration character. Forms of manganese and distribution in soil profile of them reflect genetic properties of soil. So, study on the variation of manganese content and form distribution in soil is very significant to illustrate soil genetic properties.Presently, study on mangannese content and form distributing in different soil profile was only about typical paddy soil in some district. And that, these studies often compared content of manganese and iron, and their oxides in paddy soil profiles. There are few reports about sampling soil profiles in large area and systemic analysis on every form manganese in soil, especially study on manganese content and distributing character in main type soil profiles in Chongqing.This paper chose 29 soil profiles as study object, which were sampled from Liangping County, Zhongxian County, Dianjiang County, Fengdu County, Nanchuan County and Yongchuan County. Classification extraction used sequential extraction for trace elements in soil. Every form manganese content, distributing character and movement law in soil derived from different parent material were all studied in this paper and the aim is to definitude manganese content, distributing character in soil profiles, and find the effect and variety rules of manganese in soil develop process, and then to find variety property and genetic significance, providing accordance for soil classification and nutrition regulation. The main results are as follows:(1)The order of total manganese and every form manganese contents in A horizon is as follows:Total Mn: purple parent materials(67.1～539 mg/kg)>limestone parent materials(259～341 mg/kg)> alleviation parent materials(86.2～314 mg/kg)>acid sandstone parent materials(60.3～263 mg/kg).Exchangeable Mn content in A horizon is veryly relative to parent material and pH value: acid sandstone parent materials(4.4～6.0)>purple parent materials(4.2～8.0)>alleviation parent materials(4.4～6.9)> limestone parent materials(6.3～8.0).(2)The variety rules of total Mn and every form Mn in soil profiles are as follows: as profile horizon deepen, total Mn content increases, and easily reductive Mn and MnO illuviates significantly in P or W horizon, and variation rules of carbonate compounded Mn is the same as carbonate in soil profiles, while organism compounded Mn decreases, and variation rules of amorphous Fe compounded Mn is in accordance to total Mn, but exchangeable Mn content has no obvious rules.(3)Under the condition of different development degree, every form Mn content decreases with development degree deepening, but their variation trend is relative to total Mn content and carbonate content.(4)Soil use manner has important affect on distributing of Mn in soil profile. Alluviation of Mn in dry land and orchard soil is much more weakly than that in paddy soil and dry-water alternated soil.(5)Soil pH is verily relative to exchangeable Mn and carbonate compounded Mn. Exchangeable Mn content decreases with pH increasing in dry land soil, but in paddy soil, exchangeable Mn content increases when pH increases. The correlation coefficient between the percentage of exchangeable Mn content to total Mn content and soil pH value is -0.418, reaches verily markable level(R_0.01=0.267, n=95).The variation rule of carbonate compounded Mn content is the same as soil pH value, the correlation coefficient between them is 0.645, also reaches verily markable level(R_0.01 =0.505,n=24).