Evaluation Of Cultivated Land Fertilit At Yongning County Based On GIS

It has been30years since the second soil survey in Ningxia province. With the change of ecological environment and socio-economic,the fertility of the cultivated land has also been changed greatly. Since the nationwide Soil Testing and Formulated Fertilization Project in2005, the project counties have collected a large number of soil samples, but the evaluation work on the production potential of the cultivated land haven’t been systematically carried out. Therefore, based on the collected soil survey data in the Soil Testing and Fertilization Project, by means of GIS and other relative technology, this study will undertake the evaluation and analysis of the production potential of the cultivated land in Yongning County-a typical region in Yellow River irrigation area. The purpose of this study is to explore the methods for evaluating the fertility of the cultivated land by using GIS, and from a special perspective, to analyze the distribution features and dynamic changing trends of the cultivated land levels, nutrient, salinization and medium-low yield fields, in order to provide data support for the rational development and utilization of the arable land and protection of the cultivated land quality in Yellow River irrigation region in Ningxia province.Firstly, the remote sensing images, second Soil Survey papery map, topographic raster map(l:50000) of Yongning County Spot5are processed by means of regulation, correction, spectrum selection, fusion and so on with the software of Erdas8.7. And then on the platform of ArcGIS9.3, interpret them into the cultivated land distribution vectorgraph, the soil type vectorgraph and the fundamental geographic information vectorgraph, based on which and on nutrient difference chart generated from sampling points, the cultivated land evaluation unit graph will be interpreted by GIS special analysis method. Thirdly, this study will calculate and ascertain the cultivated land evaluation index and standard by using Delphi, AHP, and fuzzy mathematics. Finally, the cultivated land comprehensive index method will be established to assess its fertility. Moreover, on the basis of the assessment, this study will undertake the space-time distribution research of the cultivated land level, soil nutrition and medium-low yield land, coming up with the measures for the utilization and protection of the cultivated land. The main study results are as follows:1. The high-yielding lands (the1st and2nd level fields), covering39.8%of the total cultivated land in Yongning County, mainly distribute in the towns of Lijun, Wanghong and Wangyuan of Yongning County, alongside the canals of Huinong and Hanyan. The medium-low yield field (the5th and6th fields), covering10.2%of the cultivated land, mainly distribute in the town of Minning, Yongning County, to the west of Xigan canal.2. The content of organic matter, available phosphorus, available potassium,and alkali-hydrolysable nitrogen in soil of Yongning County’s cultivated land is moderate with the respective average content of13.51g/kg,23.85mg/kg,144.39g/kg,60.97g/kg, and thereinto, the content level of organic matter, available phosphorus, available potassium, and alkali-hydrolysable nitrogen in the1st and2nd level lands is much higher than that in the5th and6th level lands. The content of organic matter and available phosphorus in the cultivated land of Yongning County has increased since1981to2005, that of total nitrogen and alkali-hydrolysable nitrogen is almost the same, and that of available potassium is decreasing-the organic matter increased by0.91g/kg, available phosphorus increased by5.65mg/kg, and available potassium decreased by53.41mg/kg.3. Poor fertility and the desertificated medium-low yield land respectively covers18.43%and0.75%of the total medium-low yield land, mainly distributing in the sierozem and sandy land in the town of Minning. Saline-alkali land covers20.52%of the total cultivated land, mainly distributing in the low-lying land around Tanglai canal and lakes and flood land. And hierarchical obstacle land covers60.30%, mainly distributing in the south of Yanghe town, in the middle land of the Hanyan and Tanglai canals and also in the area to the north of Yanghe town, from the east of Hanyan canal to the region along the Yellow River.This study shows that the method based on GIS technology for evaluating and analyzing the fertility of the cultivated land is more scientific, accurate, and convenient. From different space dimension, this paper uses this method for visually quantitative analysis of the distribution features and dynamic changing principle of the cultivated land level, nutrition, salinization and low-yielding land. The study results are practical to the agriculture structure adjustment, agriculture development plan, protection and construction of the cultivated land quantity and improvement of medium-low yield field in the Yellow River irrigation region in Ningxia province.