Soil Quality Evaluation Based On Gis For Cultivated Land

It is widely known that our country, China, owns the biggest population in the world leading to a relative shortage of cultivated land resources. Cultivated land soil fertility and the pollution degree of heavy metal on soil will be directly influence some big issues, like the sustainable development of agriculture and food security. To a large extent, to carry out the soil quality evaluation on cultivated land as well as to make the situation of soil fertility and pollution brought by heavy metal clear is of great importance to build the foundation of strengthening the construction of cultivated land quality and environmental protection. This study shows the result of researching in487soil samples which are got by sampling investigation on cultivated land soil in Shibeiping Town in Liuzhou. Meanwhile, in this study, it makes analysis on the basic physical and chemical properties of soil, including organic matter(OM)、pH、total nitrogen(TN)、available phosphorus、available potassium、slow-available and bioavailability of Cu, Zn and Mn. Besides, supported by geographic information system (GIS) and applied geostatistics theory, I make full research on the spatial variability and spatial distribution of some bioavailability of heavy metals (Cu、Zn、Mn); furthermore, I also make evaluation on some heavy metals (Cu、Zn、Mn) by carrying out the single factor index. As a result, the main conclusions are showing as follow:1.The result of making analysis on the basic physical and chemical properties of soil:the mean value of soil OM in arable land in research area is22.2g/kg which is a little lower than medium level; the soil pH value is in the range from3.1to7.5accompanied by62.25%of the total has pH value less than5.5; the mean value of available phosphorus is19.7mg/kg and it majors in the medium level (48.9%of cultivated land) and the riches level (32.70%of cultivated land); the mean value of available potassium is125mg/kg which majors in the exceeding riches level (33.10%of cultivated land) and the riches level (47.74%of cultivated land); loam occupies the major part of the soil which shows its relative good water and fertility retention capacity.2. The database of cultivated land ferrility evaluation of Shibeiping Town is established by ArcGIS. According to Integrated Fertility Index (IFI) and making use of Cumulative Frequency curve method, cultivated land in Shibeiping Town in Liuzhou can be divided to six levels. To be specific, there is6,906.7hm2of cultivated land totally. Among all cultivated land,0.01%of the total (0.5hm2) is recognized as first level;1.46%of the total (100.9hm) is divided as the second level;650.0hm2of cultivated land which accounts for9.41%is the third level;2,240.3hm of cultivated land that occupies32.44%is the fourth level; besides, there is3,556.6hm2of cultivated land which accounts for51.50%in total belonging to fifth level; at last, the rest part (5.19%) of cultivated land (358.3hm2) is recognized as the sixth level. It can be seen clearly from the evaluation result that the medium-yield cultivated land is the major part in Shibeiping Town while the high-yield cultivated land (1.47%) and low-yield cultivated land (5.19%) shows that the cultivated land fertility belongs to medium to low.3. The result of making spatial analysis on bioavailability of heavy metals in soil:in the cultivated land in research area, the content of bioavailability of heavy metals (Cu、Zn、Mn) is relatively low, and the nugget effect value of them is50.2%、56.4%and50.1%respectively which shows a medium-level spatial correlation. In spatial distribution, it is can be seen after Kriging by ArcGIS that bioavailability of Cu and bioavailability of Zn have similar change features:they are higher in the north and south part of the center of the research area (a machinery manufacturing company) and lower in the east part and west part. Bioavailability of Mn accumulates too much in the northern accompanied with it gradually accumulates from the south by west to the southwest direction.4. The evaluation result of heavy metals content on soil indicates that in Shibeiping Town in Liuzhou:based on Toxicity Characteristic Leaching Procedure (TCLP) international standard, from the content degree of heavy metals brought by single factor indexs, in99.56%of soil samples, single factor contaminant indexes of bioavailability of Cu and Zn are evaluated to be at security level.