Abstract:As an important component of protein and an essential element for plants, animals and human beings, adequate supply of nitrogen in the crop production-animal production-food-household consumption system is necessary. In addition, because of the imbalance of nitrogen between production and consumption, a large amount of nitrogen frequently flows in different regions. Huang-Huai-Hai, located in the east of China, is an important base of agricultural products. And with the increasing food demand of Beijing and Tianjin, the nutrient flows between different provinces of Huang-Huai-Hai are common.
Material Flow Analysis (MFA) is a cluster of various kinds of analytical methods, which has been extensively used in environmental assessment. MFA approach is based on input output analysis (IOA) and has been extended to various sections. Based on MFA approach, the model of nitrogen flow among regions was established and the mount of nitrogen flow in “resources-fertilizer-farmland-livestock-family-environment” system was obtained.
The surplus and deficiency rate of fertilizer、feed、plant food and animal food was 33%、-120%、38%、65% respectively in 2005 in Huang-Huai-Hai. The driving force of nutrient flow in local food chain is the potential nutrient. But the factor of population、urbanization、arable land area、GDP、transport distance、transport price、market price and policy etc also have influence on it. In 2005, the area of Huang-Huai-Hai is the source of nitrogen of fertilizer and food, and the sink of nitrogen of feed. But in Beijing, nitrogen of fertilizer, food and feed all is the sink. The average cropland load of nitrogen which comes from other provinces is 872 kg/hm2, which still have a lot of risk to environment even though all this nitrogen been returned to the cropland. So the collaborative management of nutrient should be carry on in Beijing-Tianjin metropolis circle immediately.