添加生物炭和硝化抑制劑對土壤氮物種轉化和溫室氣體排放之影響

Abstract

氧化亞氮(N₂O)是一種強效的溫室氣體，主要來自農業系統中氮肥施用後土壤硝化與反硝化作用所產生的排放。為提升氮肥利用效率並減緩溫室氣體排放，生物炭與硝化抑制劑(nitrification inhibitors, NIs)被廣泛研究，但兩者交互作用的影響仍不明確。本研究透過兩項盆栽試驗，探討生物炭與硝化抑制劑對稻作與麥作期間土壤 N₂O 排放通量的影響。第一項試驗為水稻盆栽實驗，分別在湛水與排水兩種水分管理條件下，設計三種處理：僅施用氮肥、施用氮料與生物炭、以及施用肥料、生物炭與硝化抑制劑；第二項試驗則為小麥盆栽實驗，處理包含不同生物炭施用量與硝化抑制劑的組合。分析在實驗週期中的土壤氮物種(NO2--N, NO3--N and NH4+-N)、溫室氣體(CO2, CH4 and N2O)通量及氮功能性基因(AOA amoA, AOB amoA, nirS and nirK)。研究結果表明，生物炭與硝化抑制劑對氮物種轉化及 N₂O 排放的影響，受到水分管理條件顯著影響。在稻作湛水條件下，單獨施用生物炭會促進後期硝化作用，可能導致 N₂O 排放增加；然而結合硝化抑制劑使用，則有效抑制硝酸鹽累積。相較之下，在排水條件，施用生物炭顯著降低 N₂O 排放並抑制硝酸鹽累積。於小麥盆栽實驗中，較高劑量的生物炭施用會延緩硝化作用並降低初期 N₂O 排放，且與硝化抑制劑呈現協同作用，有效減少氮損失。功能性基因分析亦顯示，生物炭與硝化抑制劑對微生物群落具有不同影響：生物炭可提升硝化菌豐度，而硝化抑制劑則抑制其活性。本研究強調生物炭、硝化抑制劑與水分管理之間的複雜交互關係，並指出透過優化生物炭的施用策略，可有效提升氮的滯留、減緩溫室氣體排放，進而促進農業永續發展。

Nitrous oxide (N₂O) is a potent greenhouse gas primarily emitted from agricultural systems duo to soil nitrification and denitrification processes with nitrogen fertilizers. To enhance nitrogen use efficiency and mitigate greenhouse gas emissions, biochars and nitrification inhibitors (NIs) have been explored, yet their combined effects remain unclear. This study investigates their influence on soil N₂O fluxes during rice and wheat cultivation through two pot experiments: a rice-cultivation experiment under flooded and drained conditions with the treatments of fertilizer alone, fertilizer with biochar, and fertilizer with biochar and NIs; a wheat-cultivation experiment under dryland conditions with varying biochar application rates and NI combinations. Soil nitrogen speciation, greenhouse gas fluxes, and functional microbial genes were analyzed. The results indicate that biochar and NIs influence nitrogen transformations and emissions differently across water management conditions. Under flooded conditions during rice cultivation, biochar alone promoted late-stage nitrification, potentially leading to increased N₂O emissions, while the combination of biochar and Nis effectively suppressed nitrate accumulation. Comparatively, under drained conditions, biochar application significantly reduced N₂O emissions and suppressed nitrate accumulation. In the wheat-cultivation experiment, higher biochar application rates delayed nitrification and reduced early-stage N₂O emissions while showing a synergistic effect with NIs in limiting nitrogen losses. Functional gene analysis revealed that biochar and NIs affected microbial communities differently, with biochar enhancing nitrifier abundance while NIs suppressed their activity. These findings highlight the complex interactions between biochar, NIs, and water management, suggesting that optimized biochar application can enhance nitrogen retention and mitigate greenhouse gas emissions, contributing to sustainable agricultural practices.