有机无机肥料配施对春玉米农田N2O排放及净温室效应的影响

为了明确有机无机肥料配施条件下华北旱地春玉米农田N2O周年排放规律、影响因素及其净温室效应，采用静态箱-气相色谱法和生物地球化学模型（DNDC）相结合的方法，对单施化肥（NPK）、有机无机肥料配施（50％M＋50％U）、单施有机肥（M）、对照（CK）等处理的春玉米农田N2O排放情况进行了周年监测，并对DNDC模型进行验证，利用验证后的模型定量评价了不同施肥处理的净温室效应。结果表明：不同有机无机肥料配施处理N2O放通量具有明显的季节变化规律，通量变化范围是-17．56—157．25μg·m2·h-1，在非生长季观测到明显的N2O排放峰，最大排放通量为83．85μg·m2·h-1。NPK、50％M＋50％U、M、CK处理周年累计排放量分别为1．49、1．20、0．82、0．61kgN·hm-2·a-1，非生长季排放总量分别占全年总排放量的40．6％、59．2％、61．7％和60．7％，非生长季N2O排放不容忽视；在整个周年观测期内，当土壤水分含量介于19％-37％之间时，各处理下的N2O通量同土壤含水量呈极显著正相关关系。综合考虑整个农田生态系统碳收支平衡和温室气体排放，经过DNDC模型模拟表明有机无机肥料配施同单施化肥处理相比净温室效应减少33．5％，可以达到在保持产量的基础上“减排”和“固碳”的协同效果。上述研究结果为有机无机肥料合理使用以及旱地农田“稳产、减排、固碳”相协调施肥技术的筛选提供了科学依据。

Nitrous Oxide Emissions and Net Greenhouse Effect from Spring-maize Field as Influenced by Combined Application of Manure and Inorganic Fertilizer

Nitrous oxide（ N2O） is one of atmospheric greenhouse gases generated from dryland agro-ecosystems. Seeking its mitigation measures is a hot topic in global climate change studies. We investigated how the fertilizer application strategies could affect N2O emissions from the agricultural soils in the North China. The field experiment was conducted in Qianxi County, Hebei Province. Nitrous oxide fluxes were measured using static chamber-gas chromatography from November 2011 to November 2012 at the spring maize fields with four different treatments, i.e., chemical fertilizer（ NPK ）, manure fertilizer（ M ）, combined manure and chemical fertilizer（ 50%M＋50% U ）, and Control （CK）. The DNDC model, which was validated against data sets of N2O fluxes observed in the experiment, was used to estimate the net greenhouse effects of different management practices and their long term impacts on soil organic carbon （SOC） dynamics. Nitrous oxide emissions from the spring maize fields under different treatments had similar seasonal patterns, varying from -17.56μg·m^-2·h^-1 to 157.25μg·m^-2·h^-1. Obvious N20 emission peaks were observed during the freeze-thaw period, with a maximum flux of 83.85μg·m^-2·h^-1. The annual cumulative N2O emissions were 1.49, 1.20, 0.82 kgN·hm-2·a-1 and 0.61kgN·hm-2·a-1, and the N2O emitted during non-growing seasons was 40.6%, 59.2%, 61.7% and 60.7% of the annual N2O emissions, for treatments NPK, 50%M＋50%U, M and CK, respectively. Nitrous oxide fluxes had a significant positive correlation with soil moisture（WFPS） when WFPS ranged from 19% to 37%. However, there was no significant correlation between them when WFPS was from 37% to 70%. A significant positive correlation was found between N2O fluxes and soil temperature（5 cm） under the conditions of suitable soil moisture and abundant substrate. Combined application of synthetic fertilizer and manure could reduce the net greenhouse effect by 33.5%, without decreasing crop yields. In addition, this treatment had positive effects on long-term SOC dynamics（50 years ）. It is concluded that implementation of manure amendments would effectively mitigate greenhouse gas emissions and increase the SOC in agro-ecosystem.