菜地追施猪粪沼液后NH_3和N_2O排放特征及氮损失率

NH_3 and N_2O emission and nitrogen loss rate from biogas liquid produced by pig slurry after topdressing on vegetable fields

将厌氧发酵残留物作为肥料还田是其资源化利用的有效途径，但国内外对其还田后氨气（NH3）和氧化亚氮（N2O）的排放特征及氮素利用率的报道较少。本研究通过微区试验，探讨了冬季和夏季大棚菜地追施猪粪沼液（DPS）后NH3和N2O的排放速率及氮素损失率。结果发现， 追施DPS后菜地NH3挥发激增，通常发生在施肥后的48 h 内；而N2O排放量在第一次施肥后大幅增加，随后逐步趋于稳定。追施DPS的处理其NH3和N2O的排放量均显著高于施用化肥的处理，冬季和夏季二者的损失量分别占肥料总量的16.4%～23.2%和24.7%～27.5%。土壤温度、水分和pH对沼液中氮素以NH3和N2O的形式损失的影响较大。

Application of the byproducts from anaerobic digestion of animal manures is a promising solution in recycling animal wastes as resources. By the end of 2008, about 0.13 billion tons of liquid and solid digested residues have been produced in China. The predominating portion of which is in liquid state. The produced biogas liquid after anaerobic digestion is characterized by the high concentrations of dissolved organic carbon （DOC）, nitrogen （N）, potassium （K） and phosphorus （P）. These digested slurries are very often applied on the top of vegetable fields not only as valuable nutrient resources, but also increases soil fertility and plant nutrition. As the high availability of the nutrients in biogas slurry, N loss would happen through ammonia （NH3） volatilization and nitrous oxide （N2O） emission. To understand the loss of N after topdressing of biogas liquid from anaerobic digested pig slurry （DPS）, a field experiment was carried out in a vegetable greenhouse in winter and early summer. The NH3 and N2O emissions were assessed and soil dissolved mineral and organic nitrogen contents were determined, the nitrogen loss and N efficiency of biogas liquid were calculated and the key drivers of the dynamics in soil NH3 and N2O emissions were discussed. The results showed that NH3 emission was observed immediately following every topdressing time of DPS and tended to increase in the following 48 h. The N2O emission was burst after the first topdressing time, and slightly increased in the subsequent topdressing periods and the emission rate tended to be steady. The average NH3 and N2O emission rates from DPS treatments were significantly higher than those from chemical fertilizer. Overall 16.4%-23.2% of the N contained in the biogas liquid lost through NH3 and N2O emissions in winter, and 24.7%-27.5% lost in summer. The temperature, water and pH conditions in soil should bring enough attention with regard to the fertilizer with high concentrations of NH＋4-N, NO-3-N and DON.