Geochemical evaluation of land quality in China and its applications

The evaluation of land quality is fundamental for land use planning. The geochemical evaluation of land quality in China is a basic part of the Multi-purpose Regional Geochemical Survey Project, which classifies land quality based on soil nutrients (e.g., N, P, and K), harmful elements (e.g., As, Cd, Cr, Hg, and Pb), pH, and soil organic carbon content. This project also classifies land quality using indicators, such as air quality, irrigation water quality, and agricultural products safety, and accordingly evaluates land management. This study introduces the scale, unit, indicators, criteria, and grade classification of the evaluation system. Taking the geochemical evaluation of national land quality as an example, we introduce the results for soil nutrient, soil environment, and comprehensive geochemical classifications of land quality in the primary farming areas of China. The results indicate that the proportions of high quality and excellent soil are 47.5% and 38.1% of the total study area, respectively, which are widely distributed in the major grain-producing areas of China. These results can be widely applied for land use planning, improvement of land production potential, and for the prevention and control of endemic diseases. The geochemical evaluation of land quality in China is still in its infancy. Thus, the evaluation methods need further improvement. In addition, some problems arise in the integration of these methods with the existing agricultural land classification and grading systems in China. Many aspects of the current evaluation system, such as methods for obtaining and interpreting results, need to be improved to fully reflect the quality of cultivated land in China and to be in accordance with developed countries worldwide.