The objectives of this study were to obtain rational irrigation and nitrogen (N) management for reducing methane (CH 4 ) emission from paddy field and understand how CH 4 emission flux is affected by the changes in soil enzyme activities and organic carbon fractions under different irrigation and N management. Two-season field experiments were conducted with three irrigation modes, conventional irrigation (C), “thin-shallow-wet-dry” irrigation (T), and alternate drying and wetting irrigation (D), and two N treatments, 100% urea (FM1) and 50% urea and 50% pig manure (FM2), to investigate CH 4 emission flux, soil enzyme activities, and organic carbon fractions and analyze the relationships between them. CH 4 emission fluxes from early and late rice fields peaked at tillering stage (652.74 and 103.78 mg m −2 h −1 ). Compared to C mode, D and T modes increased early rice yield and D mode also increased total yield of both seasons. However, D and T modes decreased cumulative CH 4 emissions over the whole growth period under FM2. CH 4 emission flux was positively correlated with saccharase activity and microbial biomass carbon (MBC), but negatively correlated with cellulase activity. Path analysis indicates that cellulase activity had a direct negative effect on CH 4 emission. FM2-D and FM2-T were rational irrigation and fertilizer treatments for rice production with higher yield and lower CH 4 emission, and CH 4 emission flux was affected by the changes in MBC, saccharase, and cellulase activities in soils under different irrigation and N management.

中文翻译：

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不同灌溉施氮条件下华南水稻土酶活性及有机碳分数相关的甲烷排放

本研究的目的是获得合理的灌溉和氮（N）管理以减少稻田甲烷（CH 4 ）排放，并了解不同灌溉条件下土壤酶活性和有机碳含量变化对CH 4 排放通量的影响。和 N 管理。两季田间试验采用常规灌溉（C）、“薄-浅-湿-干”灌溉（T）和干湿交替灌溉（D）三种灌溉方式，以及2个N处理，100%尿素(FM1) 和 50% 尿素和 50% 猪粪 (FM2)，研究 CH 4 排放通量、土壤酶活性和有机碳分数并分析它们之间的关系。早稻田和晚稻田的CH 4 排放通量在分蘖期达到峰值（652.74 和103.78 mg m -2 h -1 ）。与C模式相比，D 和 T 模式增加了早稻产量，D 模式也增加了两个季节的总产量。然而，在FM2 下，D 和T 模式在整个生长期减少了累积CH 4 排放。CH 4 排放通量与蔗糖酶活性和微生物生物量碳（MBC）呈正相关，但与纤维素酶活性呈负相关。通径分析表明纤维素酶活性对CH 4 排放有直接的负面影响。FM2-D和FM2-T是水稻增产、低CH 4 排放的合理灌溉施肥处理，CH 4 排放通量受不同灌溉条件下土壤MBC、糖酶和纤维素酶活性变化的影响管理。D 和T 模式减少了FM2 下整个生长期的累积CH 4 排放。CH 4 排放通量与蔗糖酶活性和微生物生物量碳（MBC）呈正相关，但与纤维素酶活性呈负相关。通径分析表明纤维素酶活性对CH 4 排放有直接的负面影响。FM2-D和FM2-T是水稻增产、低CH 4 排放的合理灌溉施肥处理，CH 4 排放通量受不同灌溉条件下土壤MBC、糖酶和纤维素酶活性变化的影响管理。D 和T 模式减少了FM2 下整个生长期的累积CH 4 排放。CH 4 排放通量与蔗糖酶活性和微生物生物量碳（MBC）呈正相关，但与纤维素酶活性呈负相关。通径分析表明纤维素酶活性对CH 4 排放有直接的负面影响。FM2-D和FM2-T是水稻增产、低CH 4 排放的合理灌溉施肥处理，CH 4 排放通量受不同灌溉条件下土壤MBC、糖酶和纤维素酶活性变化的影响管理。通径分析表明纤维素酶活性对CH 4 排放有直接的负面影响。FM2-D和FM2-T是水稻增产、低CH 4 排放的合理灌溉施肥处理，CH 4 排放通量受不同灌溉条件下土壤MBC、糖酶和纤维素酶活性变化的影响管理。通径分析表明纤维素酶活性对CH 4 排放有直接的负面影响。FM2-D和FM2-T是水稻增产、低CH 4 排放的合理灌溉施肥处理，CH 4 排放通量受不同灌溉条件下土壤MBC、糖酶和纤维素酶活性变化的影响管理。