Abstract: Taking a small watershed at the upstream of Dahuofang Reservoir in the upper reaches of Hunhe River as the study area, this paper analyzed the non-point source nitrogen pollution characteristics of different farmer types. According to the nitrogen flow characteristics in the watershed, the farmers were classified into three types, i.e., livestock and poultry- based farmers, vegetable growers, and traditional farmers. The nitrogen pollution loads of the farmers were in the order of livestock and poultry- based farmers (348±76 kg·hm^-2·a^-1) > vegetable growers (307±127kg·hm^-2·a^-1) > traditional farmers (213±126 kg·hm^-2·a^-1), and the nitrogen losses from the lands of the farmers were in the order of vegetable land (256±21kg·hm^-2·a^-1) > livestock and poultry- based land (188±52 kg·hm^-2·a^-1) > traditional farmland (168±65 kg·hm^-2·a^-1), indicating that the vegetable growers and livestock and poultry-based farmers in the watershed had greater contribution to the water quality, being the priorities of consideration for the prevention of the non-point source nitrogen pollution. As for the nitrogen pollution sources, inhabitant living and farmland nitrogen losses occupied 28% and 72%, respectively, suggesting that farmland was the main source of nitrogen pollution, whereas inhabitant living was the another important source not be ignored. The threshold of the optimal nitrogen cycle in the study area was 395.5 kg·hm^-2·a^-1, and the corresponding total nitrogen flow and nitrogen output were 1883.3 kg·hm^-2·a^-1 and 376.7 kg·hm^-2·a^-1, respectively.

Key words: Copper mine tailings, Legumes, Seed germination, Seedling growth, Inhibition