GIS-based National Soil Quality Assessment Methodology And Its Application

China is a big country and agriculture plays an important role in its national economy development in its long past history and future. The demand for increased production is acute as the arable land per capita is limited due to its enormous population and fast urbanization. This situation cannot be changed in a short term along with the vigorous industrial development and the inevitable population rapid growth in the next 30-50 years. The constant improvement in agro production leads nutrient imbalance, soil nutrients being depleted, soil's physical characteristic deteriorating, and the soil fertility getting worse and worse in the long term. Nowadays the decrease of arable land and population explosion is a big concern to all the Chinese society, research and government entities. Declining soil fertility and soil quality, as well as soil contamination and food safety cause great concern. Therefore, it is so important to research on the technical, practical and organizational aspects to meet the demand of the national soil quality assessment.This dissertation uses modern soil resource management theory, integrates knowledge of geography information system (GIS) technology, establishes nationwide arable land fundamental fertility indicators system, discusses the methodology and the framework of nationwide information system (national, provincial and county level) based on WebGIS and distribute database technology, establishes GIS-based county level soil resource management information system, and carries out a case study based on Qingzhou city of Shandong province as example, implementing soil quality assessment and soil fertility status and environment quality status analyzing, and bringing forward facts and suggestions for policy-makers and crop growers. To summarize, the following five main topics is the main focuses in the dissertation:1. Establishing the national soil fertility indicators system. The paper creates a method by which a three-level (national, provincial and county) indicators system meets the needs of the different purposes for soil quality assessment in different levels and scales. At the national level, experts from the main agro universities, research institutes and extension services were invited to give as much as possible soil indicators to make a whole temporary list including their names, definitions, measurements, and then specific meetings organized to study the relationship between all the indicators, and to select indicators from the list and then build up the national level soil quality indicators system. At the provincial and county levels, local experts are organized to study and choose from each upper list to build up their own indicator systems.2. Discussing the methodology and the structure of nationwide soil information system based on WebGIS and distributed database technology. The national arable land resource management information system includes three main parts. Firstly, establishing the multilevel information network system to enhance the task instruction, data and information communication among national, provincial and county level, so that the efficiency of national soil management will be greatly improved. Secondly, establishing the multilevel database pertaining to soil quality assessment project. This database includes national provincial level digitalized map and attribute data. Every county develops its own alike local database. Thirdly, developing and distributing the nationwide multilevel arable land resource managementinformation system, each level will be working on its own system to finish its soil fertility and soil quality assessment. However, national and provincial level will certainly collect, select and analyze most of attribute data from the lower level database.3. Establishing county level arable land resource management information system (CLALRMIS). CLALRMIS mainly contains data input system, database, model, method and knowledge library, and man-computer interaction system. It integrates GIS technology, GIS module technology and obje...