Quantification Of Soil Vertic Characteristics And Its Influencing Factors

Xinjiang's research on verti soil has been in a blank state,and the study of vertisols in other regions of China has become more and more mature.By comparing the difference of vertisols between Xinjiang and other regions,it has important guiding significance for later soil investigation.Twenty-nine soil profiles with vertic characteristics were described in the northern of Tianshan mountain of Xinjiang around Changji,Hutubi County,Karamay,Yining and Urumqi counties.Through field investigation and laboratory analysis,different soil vertic characteristics and its influence factors were analyzed.By collecting the published data related to vertic soils,comparing the difference of soil vertic characteristic with Xinjiang and other provinces and cities,in order to distinguish more objective analysis of Xinjiang vertic soil and other provinces,based on the survey of 93 vertic soil profiles in different climatic zones in China.According to varied vertic soils diagnostic criteria of Chinese Soil Taxonomy(CST),Soil Taxonomy(ST)and World Reference Base for Soil Resources(WRB),the field soil vertic characteristics in observing and describing were systematically studied.The soil vertic index system was established to evaluate the soil vertic index.The soil vertic characteristics of the study area were quantified and normalized,and the influence factors and evolution mechanism of the clay content and precipitation on the vertic index were discussed.In order to compare the regional differences of soil vertic between Xinjiang and other provinces /regions,Based on the results of Xinjiang <0.002 mm clay and X-ray diffraction,the relevant data of clay minerals in other 12 provinces/regions were collected.The difference of clay,smectite and linear expansion coefficient(COLE)of 154 sections in different provinces/regions was compared and the correlation was analyzed.The following results were obtained:Firstly,Changji West Canal,Manasi county and Wuyi farm has the phenomenon of soil vertic characteristic.Yining County Youth farm survey profile diagnostic features as follows: full profile clay(<0.002mm)content reached to 323-454g/kg,While the organic carbon content is low,subsoil substitution amount reached 24.31-34.61cmol/kg,suggesting that clay itself had higher substitution,and the substitution amount/clay% ratio stands for contains abundant expansive clay mineral,Such as smectite and illite/smectite.therefore soil had higher activity and swell-shrink performance,coefficient of linear extensibility is up to 0.13cm/cm.Calcium carbonate content in the whole profiles reaches the standard of calcium criterion.Soil p H is 8.3-8.7,there was no alkalization phenomenon.Combined with the shape of the shuttle/wedge structure,slickenside and cracks and so on to meet the diagnostic features of vertic soil.Secondly,the main factors affecting the spatial variability of field soil vertic are clay content,linear expansion coefficient(COLE)and precipitation.Because of the significant spatial differences in these factors,the regional soil degeneration intensity is significantly different.With the increase of clay content,COLE and field vertic index showed an increasing trend.There was a significant positive correlation between field soil vertic index and clay content,COLE and precipitation.The results showed that field soil vertic index was not only related to internal clay content,but also influenced by the external conditions of precipitation.Thirdly,Xinjiang soil clay minerals are I/M mixture-illite-kaolinite mineral types,there is no relative content of smectite;other provinces of clay minerals are smectite-Iraq/Mongolia mixed layer of mineral types,there are contained absolutely content of smectite,the absolute content of smectite reach to 23.5-86.8%,and the soil containing smectite has a stronger swell and shrink material foundation,that is,the soil of other provinces has a greater vertic basis than Xinjiang.The expansion and contraction characteristics of soil in Xinjiang are mainly affected by the content of I/Mongolian layer and mixed layer,while the content of smectite in other provinces is the dominant factor,and the content of smectite in other provinces is higher than that in Xinjiang soil.Fourthly,the COLE values of 0-100 cm soils in other provinces were significantly higher than those in Xinjiang,and COLE had the same regional variability as the smectite.The overall performance of the 0-100 cm was greater than the surface 0-30 cm.Fifthly,with the increase of clay,the smectite and COLE showed an increasing trend in other provinces/region,but showed a decreasing trend in Xinjiang,and smectite had a positive correlation with COLE as a whole.