Rice is an important food crop in Kenya and is the third most consumed cereal crop after maize and wheat. The high demand for rice has resulted in the conversion of wetlands to rice paddies and the increased use of fertilizer, ultimately reducing the ability of wetlands to store carbon. Consequently, emissions from wetlands of three potent greenhouse gases (GHGs): methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) have increased. This study assessed the influence of fertilizer application on GHGs emission, organic carbon and nutrient stocks in rice paddies in papyrus dominated wetlands in the Nzoia River basin in Kenya. Sampling was done on a weekly basis for the first two months, and thereafter twice per month in the Anyiko rice paddies, which is a smallholder system partly converted from the Anyiko wetland. Two replicates of three fertilization treatments (standard, control and under fertilization) were assigned randomly in six rice plots. The static chamber method was used to collect the GHGs, which were then analyzed using gas chromatography. Soil samples were collected and analyzed for nitrogen and organic carbon stocks. Statistical tests revealed no significant differences in organic carbon and nitrogen stocks among the three fertilization treatments. The mean CH4 fluxes did not differ significantly among the three treatments where mean flux for control plots were 8.30 ± 4.79 mgm−2h−1; under-fertilized plots had a mean of 6.93 ± 2.42 mgm−2h−1 and standard fertilized plots mean fluxes were 4.00 ± 6.34 mgm−2h−1. Similarly, CO2 mean fluxes were insignificantly different among the three treatments, where control plots had mean of 174.80 ± 26.81 mgm−2h−1, under-fertilized plots mean were 208.81 ± 36.20 mgm−2h−1 and standard fertilized plots mean fluxes were 248.29 ± 41.22 mgm−2h−1. However, mean N2O fluxes were significantly different among the three treatments, control plots had a mean of −3.59 ± 2.56 μgm−2h−1, followed by under-fertilized with mean of −0.59 ± 0.45 μgm−2h−1 and standard fertilized plots with mean of 4.37 ± 3.18 μgm−2h−1. In this study, different fertilization scenarios had significant effects on N2O emission but no significant effect on CO2 and CH4 emission, organic carbon and nutrient stocks. Therefore, there is need for sustainable use of wetlands to ensure a balanced role between ecosystem management and human services.

中文翻译：

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肯尼亚 Anyiko 湿地改造的小农稻田的温室气体排放评估

水稻是肯尼亚重要的粮食作物，是仅次于玉米和小麦的第三大消费谷类作物。对水稻的高需求导致湿地转变为稻田，肥料使用量增加，最终降低了湿地储存碳的能力。因此，湿地中三种强效温室气体 (GHG) 的排放量有所增加：甲烷 (CH4)、一氧化二氮 (N2O) 和二氧化碳 (CO2)。本研究评估了施肥对肯尼亚 Nzoia 河流域纸莎草占主导地位的湿地稻田温室气体排放、有机碳和养分储量的影响。前两个月每周采样一次，之后在 Anyiko 稻田每月采样两次，这是一个部分由 Anyiko 湿地改造而成的小农系统。三个施肥处理（标准施肥、对照施肥和欠施肥）的两个重复被随机分配在六个稻田中。使用静态室方法收集温室气体，然后使用气相色谱法进行分析。收集土壤样品并分析氮和有机碳储量。统计检验表明，三种施肥处理之间的有机碳和氮储量没有显着差异。三个处理的平均 CH4 通量没有显着差异，其中对照地块的平均通量为 8.30 ± 4.79 mgm-2h-1；施肥不足的地块的平均值为 6.93 ± 2.42 mgm-2h-1，标准施肥地块的平均通量为 4.00 ± 6.34 mgm-2h-1。同样，三种处理之间的 CO2 平均通量差异不显着，其中对照地块的平均值为 174.80 ± 26。81 mgm-2h-1，施肥不足的地块平均值为 208.81 ± 36.20 mgm-2h-1，标准施肥地块的平均通量为 248.29 ± 41.22 mgm-2h-1。然而，三种处理的平均 N2O 通量存在显着差异，对照地块的平均值为 -3.59 ± 2.56 μgm-2h-1，其次是施肥不足，平均值为 -0.59 ± 0.45 μgm-2h-1 和标准施肥地块平均值为 4.37 ± 3.18 μgm-2h-1。在本研究中，不同施肥情景对 N2O 排放有显着影响，但对 CO2 和 CH4 排放、有机碳和养分储量没有显着影响。因此，需要可持续利用湿地，以确保生态系统管理和人类服务之间的平衡作用。三种处理的平均 N2O 通量存在显着差异，对照地块的平均值为 -3.59 ± 2.56 μgm-2h-1，其次是施肥不足，平均值为 -0.59 ± 0.45 μgm-2h-1，标准施肥地块的平均值为 -0.59 ± 0.45 μgm-2h-1 4.37 ± 3.18 μgm-2h-1。在本研究中，不同施肥情景对 N2O 排放有显着影响，但对 CO2 和 CH4 排放、有机碳和养分储量没有显着影响。因此，需要可持续利用湿地，以确保生态系统管理和人类服务之间的平衡作用。三种处理的平均 N2O 通量存在显着差异，对照地块的平均值为 -3.59 ± 2.56 μgm-2h-1，其次是施肥不足，平均值为 -0.59 ± 0.45 μgm-2h-1，标准施肥地块的平均值为 -0.59 ± 0.45 μgm-2h-1 4.37 ± 3.18 μgm-2h-1。在本研究中，不同施肥情景对 N2O 排放有显着影响，但对 CO2 和 CH4 排放、有机碳和养分储量没有显着影响。因此，需要可持续利用湿地，以确保生态系统管理和人类服务之间的平衡作用。不同施肥情景对 N2O 排放有显着影响，但对 CO2 和 CH4 排放、有机碳和养分储量无显着影响。因此，需要可持续利用湿地，以确保生态系统管理和人类服务之间的平衡作用。不同施肥情景对 N2O 排放有显着影响，但对 CO2 和 CH4 排放、有机碳和养分储量无显着影响。因此，需要可持续利用湿地，以确保生态系统管理和人类服务之间的平衡作用。