生物质炭添加量对伊乐藻堆肥过程氮素损失的影响

为探讨高温堆肥中氮素损失的有效控制技术，研究以生物质炭为添加剂对伊乐藻与稻草混合堆肥过程中氮素损失的影响，通过静态高温好氧堆肥试验，设置了6个处理，即：CK（不添加生物质炭）、5个生物质炭不同添加量处理（以CK为基础，生物质炭添加量分别为CK堆体干基质量的6%、18%、30%、42%、54%），监测了伊乐藻与稻草混合堆肥过程中堆温、氨挥发速率等相关指标的变化。结果表明，与 CK 相比，添加生物质炭可以提高堆温、延长高温期天数、缩短堆肥周期，堆肥周期减少天数与生物质炭添加量呈极显著的对数曲线相关（P<0.01）；添加生物质炭可以显著降低堆肥过程中的氨累积挥发量（P<0.05），但与CK相比，生物质炭添加量为6%、18%处理的氨累积挥发量分别增加了26.58%、6.34%，同时，氮素损失率亦高于CK处理；堆肥过程中氮素损失率与生物质炭添加量关系密切，呈显著的一元三次曲线相关（P<0.05），生物质炭的适宜添加量为27.11%～45%；根据不同影响因子的标准偏回归系数，对堆肥体氮素损失率的影响，由大到小依次为全氮、铵态氮、有机碳。

Effect of biochar addition amount on nitrogen loss during composting process of Elodea Nuttallii

Abstract: Biochar has the potential to reduce nitrogen (N) loss during composting process mainly through mitigating ammonia or water-soluble ammonium. However, until now there is still less quantitative information on the impact of biochar amendments on the N loss as well as on the optimum addition amounts and mixture ratios of biochar and compost. To fill in this knowledge gap, in the present study, a laboratory-scale static aerobic reactor was employed in the composting process of aquatic plants (Elodea nuttallii), in which different amounts of biochar amendment were applied. This experiment was composed of 6 treatments: 1) without biochar addition under traditional operation and composting condition, named as CK; and 2) with 5 different levels of biochar addition, the addition amount were 6%, 18%, 30%, 42% and 54% of the composting dry basis given in CK treatment, named as B1, B2, B3, B4 and B5, respectively. All the treatments applied the same amount of straw of aquatic plants (Elodea nuttallii) and rice as the composting material and had consistent environmental control conditions. The dynamics of accumulated temperature, rate of ammonia volatilization, pH value as well as the content of ammonium-N, nitrate-N and soil organic carbon were observed during the process of composting. Our study revealed the following findings: 1) Compared with the conventional composting process, adding biochar could significantly increase the composting temperature and prolong the duration days of high temperature, and therefore higher cumulative temperature and shortened composting period were obtained with the application of biochar. Furthermore, there was a significant logarithmic correlation (P<0.01) between the number of reduced days in composting cycle and the amount of biochar addition. When the biochar addition was below 50%, every 5% additional biochar amendment could shorten the composting period of approximately 0.4 d. 2) During the composting process, with application of biochar treatment (biochar content of 30%, 42%, and 54%), the accumulated NH3 volatilization was significantly lower than that of CK treatment (P<0.05). However, compared to CK treatment, accumulated NH3 volatilization was increased by 26.58% in B1 treatment (biochar content of 6%) and by 6.34% in B2 treatment (biochar content of 18%), respectively, and the nitrogen loss rate was higher than that of CK treatment. The rate of nitrogen loss rate during the composting process and the content of biochar addition showed a significant correlation of cubic curve (P<0.05). The appropriate ratio of biochar to composting was from 27% to 45% (dry biomass). In addition, when the content of biochar addition was in the range of 30%-55%, every 5% additional biochar applied could reduce the rate of nitrogen loss by 4.97% on average. Under biochar amendment, different impact factors that influenced the nitrogen loss were also analyzed using standard partial regression, and it was found the effect decreased gradually in the order of total nitrogen, ammonium nitrogen and organic carbon. Overall, this study highlights that reasonable application of biochar would have a great potential to reduce nitrogen loss and enhance working efficiency in composting process, which is a promising technology in composting.