| In the new national survey of land resources, agricultural land grading is considered one of the most important projects in "Land Resource survey and Monitoring Engineering", and it will be organized all over the country by the national land resource ministry. Just in this context, this paper, utilizing Geographic Information System as a technical foundation and taking Song county as an example, studied on the method of agricultural land grading in order to test the rationalization of 《agricultural land grading regulations》 and offered some practical foundations and experimental experiences for this work which would be performed all over country.At the beginning, this paper introduced the development of land resource evaluation in the nation and abroad, and the meaning of doing it, then talked about the theories and technical foundations, ascertained the objects and tasks definitely, and discussed the principles and procedure of the work in detail. In the following, taking Song county as an example, it put the theories and methods of land resource evaluation into the practice of agricultural land grading by using the MAPGIS software, and divided the 47212.73 ha agricultural land in Song county into 8 classes and 5 grades. The study showed that:1. The method of the agricultural land classifying and grading is a scientific one, and its achievement is practical. First of all, it corrects the index of the yielding potential of plants decided by light and temperature through the factors such as terrain, soil, irrigation and so on, then revises the production of the agricultural land to the average conditions of utilization and economy with the land utilization coefficient and economical coefficient, and according to the above, makes the agricultural land classes, then modifying the result with such factors as land district and cultivated facility and deviding agricultural land into different grades. Therefore, this work synthetically uses the theories and methods of the using current condition appraisal, potential appraisal and suitability appraisal to the agricultural land, and takes the agricultural land using level and economic benefit into account, so the result hasmutigradation. At the same time, the achievement of the agricultural land grading which is based on CIS, is of great practicability. That is the database that GIS has set up realizes the exchange visits of graph database and property database, so that it is convenient for applying and renewing the achievement, and the achievement property database contains a great deal of soil information which is highly advantageous to know the quality condition and limited factors of every agricultural land Appraisal unit, and also supplies some foundation on using and improving the soil condition.2. GIS supplies the technical foundation for agricultural land grading and improves the speed and precision of the work. Taking GIS as technical foundation and using its ability of space analysis and data processing can save the manpower, material resources and financial capacity, accelerate the work plan, also increase the achievement precision; the agricultural land grading achievement based on GIS can conserve all original data as well as the intermediate and end achievement that makes * it convenient to revise and renew the achievement.Finally, this paper discussed the questions encountered in the practical test study, and put forward the following suggestions: Firstly, in order to assure the comparability of the evaluation achievement among the different areas, the divisional evaluation should consider all the limited factor of agricultural land qulity; Secondly, in accordance with the situation that the differences in land ultilization coefficient and economy coefficient is marked, this work need to lower its influence on the grading achievement so that it can reflect the geography law; Thirdly, the precision of agricultural land grading achievement is suitable for high but not low, so that it is easy to apply; Fourthly, while the revised factors corr... |
