Book excerpt: The study of soil nitrogen has long been an active field, but it was generally pivoted on agricultural and forestry production, and animal husbandry. With the rapid increase in the use of fertilizer nitrogen, more attention has been paid to the rela tionship between nitrogen management and environmental quality and human of soil nitrogen has become more comprehensive with health. In addition, the study the development of related sciences. The quantitative study of the processes in nitrogen cycling and their interrelationships has been an important part of this project and has attracted the attention of scientists allover the world. Nitrogen is one of the most important nutrients for plant growth and the applica tion of fertilizer nitrogen is playing an important role in agricultural production. The annual consumption of fertilizer nitrogen in the world has reached 70 million tons, and China has an annual consumption of more than 15 million tons and is the largest fertilizer nitrogen consumer in the world. However, the efficiency of nitro gen fertilizer is low and losses are large. It is estimated that nitrogen losses from agriculture in our country can be as high as 40-60% of the nitrogen applied. Some of the lost nitrogen enters the atmosphere and contributes to the greenhouse effect and some enters water bodies to pollute the water.