雞羽毛水解液在土壤中的氮轉變及其對土壤團粒穩定性和菌群的影響

Abstract

全球雞養殖業每年產生數百萬噸的雞羽毛，造成嚴重的環境問題。雞羽毛富含角蛋白，經過亞臨界水萃取，這些角蛋白可以被轉化為高氮含量的蛋白質水解液。氮是作物生長所需之巨量元素，化學肥料施用解決了作物氮肥供應的問題，但是化學氮肥大量施用卻也導致了嚴重的環境問題。因此，本研究的目的是要探討雞羽毛水解液的氮在土壤中的轉變機制，並評估其是否具有做為有機氮肥的潛力，以期解決雞羽毛廢棄物和化學氮肥施用所導致的環境問題。本研究於不同pH和質地的土壤進行60天的土壤孵育實驗，分析土壤樣品中總氮、可水解氮、銨態氮、亞硝酸態氮、硝酸態氮及氧化亞氮通量等氮物種，以及總碳、細菌群落和參與氮轉變過程的重要功能性基因(AOA amoA, AOB amoA, nirS, and nirK)隨時間的變化，並將雞羽毛水解液與尿素進行比較。孵育實驗結束後，分析土壤團粒的穩定性。結果表明，雞羽毛水解液的氮礦化作用比尿素緩慢。在黏土含量較高的酸性土壤中，生物有效性氮（可水解氮、銨態氮、亞硝酸態氮和硝酸態氮的總和）增加較少。硝化作用只在中性土壤中發生，而未在酸性土壤中發生。在中性土壤中，自營性硝化菌在硝化過程中扮演至關重要的角色。此外，雞羽毛的施用使nirS/nirK比率下降，顯示反硝化菌群的組成發生了變化。至於土壤健康指標，雞羽毛的施用使細菌群落的組成產生些微變化，但細菌總數並沒有顯著的變化。此外，土壤有機質的分解和土壤團粒的穩定性也沒有顯著的變化。這項研究表明，雞羽毛水解液可以作為有機氮肥，因為其與化學氮肥相比，對環境的影響似乎更低。

Millions of tons of chicken feathers are generated globally each year, posing significant environmental problems. Fortunately, chicken feathers are rich in keratin, which can be converted into protein hydrolysate by subcritical fluid extraction. This hydrolysate with high nitrogen (N) content has the potential to serve as an organic nitrogen fertilizer. Nitrogen is one of the macronutrients for plant growth. Since the 20th century, an increased demand for synthetic nitrogen fertilizers driven by the flourishing human population has led to severe environmental issues. Thus, understanding the mutual influence between chicken-feather hydrolysate (CFH) and soil offers a possible solution to address both feather waste problems and the environmental issues tied to synthetic nitrogen fertilizers. In this study, CFH was incubated in soils with different pH and texture for 60 days to investigate how CFH transforms in soil and how the soil is affected by CFH. N species (total N, hydrolysable N, ammonium, nitrite, nitrate, nitrous oxide), total carbon, nitrogen functional genes (AOA amoA, AOB amoA, nirS, and nirK), and bacteria community were measured over time. After the incubation ended, water-stable aggregate was measured. The findings on nitrogen dynamics of CFH revealed that the mineralization rate of CFH into ammonium nitrogen was slower than that of urea. In acidic soils with a higher clay content, there were less increases in bioavailable nitrogen. Nitrification occurred only in neutral soils but not in acidic ones. In neutral pH soils, autotrophic nitrifiers played a crucial role in the nitrification process. Additionally, applying CFH decreased the nirS/nirK ratio, indicating changes in the composition of the denitrifying microbial community. About soil health indicators, CFH application led to a minor shift in the composition of the bacterial community without significantly affecting the total bacteria abundance. Furthermore, there were no substantial change in the decomposition of soil organic matter and the stability of soil aggregates. This study suggests that CFH can function as an organic nitrogen fertilizer, as its environmental impact appears lower compared to synthetic nitrogen fertilizers.