| In order to ascertain the content,and temporal and spatial variability characteristics of major nutrients,as well as spatial distribution of heavy metals of tobacco planting soil in Longyan tobacco district,the project applies GIS technology and geostatistics,researches spatial and temporal variability characteristics of major nutrients and heavy metals' spatial distribution of tobacco planting soil in Longyan tobacco district for the first time.The findings can provide basis of decision making for balance regulation of soil nutrients in Longyan tobacco planting district,and reference for the quality safety of flue-cured tobacco production.According to the sampling points of soil census in 1982,366 soil samples with the same or similar coordinates and of the same soil types were collected at the 0-20cm arable layer of tobacco planting soil in December of 2011;meanwhile physical and chemical performance of the soil samples were tested and analyzed.The information about the tobacco planting soil in Longyan tobacco district was collected,which mainly included the second soil census data(organic matter,pH,total nitrogen,available nitrogen,total phosphorus,available phosphorus,total potassium,available potassium,etc.),relevant information about testing soil for formulated fertilization of tobacco planting soil in Longyan tobacco district in 2001(organic matter,pH,total nitrogen,available nitrogen,total phosphorus,available phosphorus,total potassium,available potassium,etc.),1:150000 administrative map of Longyan City,1:150000 arable land use map of Longyan City.Data were analyzed with the method of combining traditional statistics and geostatistics.Statistical analysis was performed through the statistical software of SPSS 18 and Excel 2007,wherein Semivariogram model fitting was achieved in GS+9.0,Kriging interpolation and interpolation mapping were chosen to be completed in ArcGIS 9.3.On the basis of getting the soil pH values,main nutrients for the three periods of 1982,2001,2011 year in Longyan tobacco planting district,and getting its heavy metal spatial distribution map in 2011,through the function of Arcgis,the main nutrition s' spatial and temporal variability were further obtained.The following conclusions were drawn:After logarithmic transformation and Box-Cox transformation of correlation coefficients,the soil pH,major nutrients,heavy metal content of Longyan tobacco planting district were in line with normal distribution;semi-variance model fitting complied with the following models:linear model,exponential model,Gaussian model,and the spherical model;as for the soil PH,major nutrients,heavy metal content of Longyan tobacco planting district,except the total potassium content of the soil in 1982 was weak spatial dependent,the rest were moderate spatial dependent and strong spatial dependent.The soil pH values were 5.34,5.03,and 5.23 respectively for the years of 1982,2001 and 2011.The soil PH suitable(slightly acidic)areas of these three periods were widest,which were 102061.65 hm2,96556.60 hm2,136125.25 hm2 respectively.The high value areas of pH in 1982 were located in the northwest part of Changting County,north-central region of Liancheng County,and the southern region of Shanghang County;in 2001,they were scattered in all counties and cities,wherein in the northwest of Changting County,southern region of Shanghang County,and central part of Zhangping City there was a wide range of high value area;in 2011,they were mainly located in these three regions:the area centering around Xinqiao Town of Changting County,the area centering around Zhongchi Township and Shifang Town of Shanghang County,as well as the northeast area of Zhangping City.The organic matter contents in Longyan tobacco planting soil were 31.70 g/kg,23.07 g/kg,and 29.04 g/kg respectively in 1982,2001,and 2011.The areas of which the soil organic matter contents were rich were widest in 1982 and 2011,which were 90980.62 hm2 and 78705.91 hm2 respectively;the area of which the soil organic matter content was in middle level was widest in 2001,which was 110402.33 hm2.The high value areas of organic matter for tobacco planting soil were located in the southeast part of Yongding County in 1982.In 2001,they were located in the northeast part of Yongding,southwest part of Wuping County,as well as the northern part of Liancheng;in 2011,they were mainly located in these three regions:the areas centering around Luofang Township and Yihe Township,the areas centering around Jiuxian Township,Baisha Town,and Jiaoyang Township,as well as the areas centering around Zhongbao Town and Taoxi Town.The contents of total nitrogen and available nitrogen in Longyan tobacco planting district in 1982,2001 and 2011 were 1.31 g/kg,1.67 g/kg,1.72 g/kg,140.82 mg/kg,140.72 mg/kg and135.07 mg/kg respectively.The soil area which potentially lack total nitrogen was widest in 1982,which was 109836.52 hm2 The soil areas of which the total nitrogen contents were in middle level were widest in 2001 and 2011,which were 109575.60 hm2 and 83508.23 hm2 respectively.The high value areas for total nitrogen in 1982 were located in the southeastern region of Yongding County;in 2001,they were located in the northeast of Yonding,and north part of Wuping County;in 2011,they were located in the two band areas stretching northwest and southeast.The soil areas which potentially lacked available nitrogen in these 3 periods distributed most widely,which were 72539.05 hm2,64370.79 hm2,and 83916.63 hm2 respectively.The high value areas for available nitrogen in tobacco planting soil in 1982 were located in the southern region of Yongding County and the west region of Wuping;in 2001,they were located in the central north part of Yongding County and the northwest part of Wuping;in 2011,they were located at the border between Wuping County and Changting County,and the border between Changting County and Liancheng County.In 1982,2001,and 2011,the total phosphorus and available phosphorus contents of Longyan tobacco planting soil were 0.50 g/kg,0.55 g/kg,0.78 g/kg,11.69 mg/kg,29.76 mg/kg,and 35.05 mg/kg respectively.In 2011,the areas rich in total phosphorus were widest,which were 136371.07 hm2;in 2001,the area of which the phosphorus content was in middle level was widest,which was 105708.83 hm2.In 1982,the low value areas for total phosphorus in tobacco planting soil were located in the west region of Wuping County and the most parts of Zhangping City;in 2001,they were located in the western part of Changting County;in 201 1,the high value areas gathered in several blocks,which appeared in all the counties and cities except Zhangping City.In 1982,the area which potentially lacked available phosphorus distributed widest,which was 118254.28 hm2;in 2001,the area of which the available phosphorus content was in middle level distributed most widely,which was 81343.94 hm2;in 2011,the area rich in available phosphorus distributed most widely,which was 135777.33 hm2.In 1982,the distribution of high value areas for available phosphorus was generally consistent with the spatial distribution of total phosphorus;in 2001,they were located in the south of Yongding County;in 2011,they were located in the border area of Yongding County and Liancheng County.In 1982,2001 and 2011,the total potassium and available potassium contents of Longyan tobacco planting soil were 21.18 g/kg,17.35 g/kg,14.72 g/kg,59.34 mg/kg,78.66 mg/kg,and 104.58 mg/kg respectively.In 1982 and 2001,the areas which potentially lacked total potassium distributed widest,which were 95658.03 hm2 and 87347.51 hm2 respectively;in 2011,the areas which lacked total potassium distributed most widely,which was 103909.82 hm2.In 1982,the high value areas for total potassium distributed in a band shape,stretching northeast-southwest,located in the midwest part of Liancheng and southeastern region of Changting;in 2001,they were located in the western region of Wuping County;in 2011,they were located in the southern region of Wuping County.The areas which potentially lacked available potassium distributed most widely in these three periods,which were 89277.12 hm2,97680.94 hm2,and 107439.53 hm2 respectively.In 1982,except Changting county,the soil of all the rest counties were relatively rich in available potassium;in 2001,the areas rich in available potassium appeared in the west part of Wuping and the northwest part of Zhangping;in 2011,they were located in the southwest of Changting and southeast part of Wuping.The contents of As,Cd,Pb,Cr,Cu,Zn in Longyan tobacco planting soil were 0.577 mg/kg,0.140 mg/kg,7.248 mg/kg,0.311 mg/kg,4.814 mg/kg and 4.023 mg/kg respectively,and the coefficients of variation were 111.96%,62.86%,86.60%,75.88%,60.86%,and 39.77%respectively.The median of each heavy metal didn't exceed the grade two indicator of soil heavy metal pollution in Fujian Province,Longyan tobacco planting soil was still clean,and could meet the needs of production for pollution-free agriculture.The spatial distribution of main heavy metals:the high-value areas of As were mainly located in the eastern and northern part of Liancheng County,the central part of Zhangping County,and scattering near Sanzhou Township of Changting County;as for Cd,there were two band-shaped high value areas in Wuping,stretching towards north and south,and there were block-shaped high value areas in the central part of Yongding as well as the northwestern part of Zhangping City;the spatial distribution of Pb was concentrated in the south of Yongding County,while in Zhangping and Liancheng County,it distributed in a zonal shape;the high value areas of Cr scattered mainly in Shanghang,Yongding,and Changting territory;the high value areas of Cu mainly distributed in the northeast part of Yongding County;the high value areas of Zn were located in the eastern border between Yongding and Shanghang. |
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