Macroscopic Features of Nitrogen Transformation and Cycling in the Agroecosystem in China and It''s Implications to Ecological Agriculture
我国农牧系统素转化循环的宏观特征与生态农业

Quantitate diagram models are developed which illustrate the macroscopic features with its temporal changes of N transformation and circulation in Chinese agroecosystem,by using a simplified model of N cycling with 3 untrient pools of crop, livestock and soil.The results indicated an increasingly intensified tendency that Chinese agriculture is becoming more inorganic and less efficient.While the total crop biomass N product,the food N supply and the proportion of animal N in total food N were increased 2.3, 2 and 4 times more respectively in Chinese crop-livestock system by the end of nineteen eighties than at the beginning of ninetenn fifties,the total production N input and N fertilizerconsumption were increased in 8 and 187 times,with simultaneous lowering in the proportion of organic to total production N input from 97% to 25%,and decreasing the production efficiency of total and inorganic N input in terms of producing main product N from 1.12 and 3.63 to 0.34 and 0.46 respectively.The supply of forage N would have to be doubled to tripled and fertilizer N consumption more than doubled in order to meet the food N demand of an improved quality for the population grown to 1.3-1.5 billions,this would brings out serious environmental consequences.Possible options of ecological agriculture strategy are also discussed in its potentials of dealing with challenges in respect to the N transformation and circulation in Chinese agroecosystem.