Environmental fate of released nitrogen from scattered-feeding duck-feces during rainy seasons in the Baiyangdian Lake Region
雨季白洋淀地区散养鸭粪中氮素去向研究

Scattered-feeding is an important duck breeding mode in the Baiyangdian Lake Rgion (BLR). During breeding, it is always hard to collect duck-feces because of the lack of concentrated breeding. Hence most duck-feces are abandoned on the soil surface. This paper stimulates a plot experiment condition to study the dynamics of released nitrogen from scattered feeding duck-feces and how they are influenced by environmental factors in BLR in rainy season of June to September. Investigation shows that during the reason part of nitrogen in duck-feces losses as NH3 and NH3 volatilization lasting for about 45 days at 8.72 kg·hm-2. The first 7 days are critical for NH3 volatilization, accounting for 82.7% of the total content. Volatile flux decreases gradually with decreasing temperature, illumination and increasing humidity and becomes insignificantly correlated with the environment factors. The load of total nitrogen loss in runoff is 10.05 kg·hm-2, with the highest proportion of particle nitrogen in the duck-feces treatment. There is increasing concentration of inorganic nitrogen in dissolved total nitrogen. Total nitrogen loss in leached water is 19.30 kg·hm-2 in duck-feces treatment, with the highest proportion of nitrate nitrogen. Under natural conditions, nitrogen loss through leaching, volatilization and runoff accounts for about 10% of total nitrogen in duck-feces. Non-mineralized nitrogen in duck-feces on soil surface plus nitrogen remaining in soil accounts for 45.09%. Once soil nitrogen content exceeds the critical value, it threatens water safety in BLR. Hence it is so urgent to adopt effective countermeasures that would eliminate hidden risks in free-range poultry in BLR.