Abstract
To evaluate the impact of human behavior (food consumption, human waste disposal and cultivation method) on nitrogen flow, a field investigation was conducted in 6 typical ecosystems of China, and various parameters were identified in the regional nitrogen balance model. The average per capita daily protein intake was 107 g. While there was no significant difference in total protein intake among the ecosystems, protein intake for all food groups except eggs did show a significant difference (P≦0.05). A difference in diet, alongside that in economic circumstances, reflected a difference in the characteristics and customs among ecosystems. With rapid economic growth, the rate of the organic recyclable nitrogen (e.g. human and animal wastes, agricultural byproducts) returned to the soil decreased, while the rate of that discharged into rivers increased. Regarding the annual per capita potential nitrogen load from human waste, there was a large difference between urban and rural regions; in urban areas approximately 1.02 kg N is returned to farmland and 5.49 kg N is directly discharged into rivers, while in rural regions approximately 4.33 kg N is returned to farmland and 1.60 kg N is directly discharged into rivers. Further, the most commonly used chemical fertilizers were urea and mixed fertilizers, and diversification of fertilizers was observed in wide areas of agricultural land with irrigation systems and that with paddy fields in plains. In the paddy field and oasis agricultural systems, many of the agricultural byproducts such as straw were generally burned, or mixed with base fertilizer and returned to the soil. In the irrigated agricultural system, over 70% of the agricultural byproducts such as wheat straw were recycled into livestock feed. In most instances, livestock excreta was reduced over time in the fields or pasturelands and occasionally abandoned in cases of large-scale breeding.
