畜禽养殖粪水酸化贮存及氮素减损增效研究进展

Progress in the mechanism for the promotion of nitrogen loss reduction during the acidification storage of animal slurry

畜禽粪水酸化贮存能够有效调控粪水贮存中微生物、环境与氮素间的作用关系,实现粪水氮素的减损增效,是一种具有广泛应用前景的关键技术。该研究系统综述了粪水酸化贮存中氮素的迁移转化机理,比较评价了常见酸化剂和不同酸化贮存工艺的应用效果,分析了酸化贮存技术对粪水氮素减损增效的影响。梳理总结得到:粪水酸化存储中氮素的迁移转化机制主要包括有机氮矿化、铵态氮固持、无机氮转化的抑制及硝化3个关键环节,可以依靠改变微生物作用和化学平衡状态实现氮素的减损;与其他酸化工艺相比,长期酸化工艺具有酸化效果更加稳定、应用范围较为广泛等优势;粪水酸化技术能够大幅降低NH_(3)排放,以及部分N_(2)O的排放,进而提高粪肥还田后土壤肥效,但不合理的酸化贮存技术及施用方式也会降低粪水肥效,甚至引起二次污染;未来应重点从氮素迁移转化路径的定量分析、复合酸化剂的开发、粪肥施用效果及风险的评估应对等方面进行深入研究。

Acidification storage of animal slurry is one of the key technologies to effectively regulate the relationship between microorganisms,environment,and nitrogen for the high reduction of nitrogen loss and efficiency in animal slurry.This review aims to systematically investigate the nitrogen migration and transformation during the acidified storage of animal slurry in recent years.Three acidifiers were used,including the strong acid,hydrolyzed acidic salt,and easily decomposed organic matter.Three types of acidizing storage were then selected,namely long-term,medium,and long-term acidizing in the storage pool and short-term acidizing in the application.Finally,the economic cost and application effectiveness were comparatively evaluated in this case.More importantly,a systematic analysis was performed on the reduction of nitrogen losses and enhancement of fertilizer effectiveness,according to the technical route in the acidification storage.Furthermore,future research directions were addressed to identify the shortcomings of existing technologies for the acidified storage of animal slurry.Specifically,the nitrogen migration and transformation in the acidification storage process of animal slurry were divided into organic nitrogen mineralization,ammonium nitrogen fixation,inhibition of inorganic nitrogen conversion,and nitrification.Two reasons were attributed to reducing the nitrogen loss in the acidification storage of animal slurry.The addition of acidifiers was one way to change the dynamic balance of+NH_(4) and NH_(3) by lowering the pH of animal slurry,in order to promote the formation of+NH_(4) while reducing the emission of dissolved NH_(3) in animal slurry.The microbial activity decreased with the decreasing pH and mineralization of organic matter in animal slurry,thus reducing the production and emission of NH_(3).The acidification storage of animal slurry reduced the NH_(3) emissions by 15%-77%.The degradation rate of nitrogenous organic compounds decreased with the addition of acidifiers,leading to the lower production of ammonium nitrogen.And the conversion rate of ammonium nitrogen to nitrate nitrogen was also reduced,thus further reducing the conversion of nitrate nitrogen to N_(2)O.To sum up,the nitrogen losses were reduced to alter the microbial action and chemical equilibrium state.In addition,the long-term acidizing process presented more stable acidizing and a wider application range during the application,compared with the medium and long-term acidizing in the storage pool and the short-term acidizing.The acidification storage of animal slurry can be expected to stabilize and retain+NH_(4) in the animal slurry.Therefore,acidification and returning to the field can improve the content of effective nutrients(such as N and P)in the soil for the high efficiency of soil fertility.However,the low efficiency of manure fertility and the secondary pollution can also be found in the unreasonable acidification storage and application in practice.It is a high demand for the quantitative analysis of nitrogen migration and transformation pathways in the process of fecal water storage,the complex acidifiers,and the post-acidification animal slurry in agricultural fields.The assessment and response to environmental risks can be launched for the research and development of acidification storage equipment in the future.