不同氮肥处理春玉米温室气体的排放

Emission of green house gases for spring maize on different fertilizer treatments

春玉米种植过程中会造成直接和间接的温室气体排放。该文采用生命周期的方法综合评估了不同施肥处理下的温室气体排放,目的是筛选出既能保证产量和经济效益,又能有效减排的措施。4种不同的施肥处理包括：当地传统施肥方式、尿素处理、硫包衣尿素、尿素添加双氰胺处理。采用静态箱-气相色谱法连续监测土壤N2O排放,并计算了不同肥料处理的N2O排放总量;计算了肥料生产、运输、农田耕作管理能源消耗、种子生产等的温室气体排放,计算了春玉米全生命周期中温室气体排放总量、单位产量、万元产出的温室气体排放量。结果表明,不同处理施肥造成的N2O排放量、全生命周期中温室气体排放总量、单位产量排放强度和净收益排放强度的排序均为传统施肥处理〉尿素处理〉尿素添加双氰胺处理〉硫包衣尿素处理。传统施肥处理的N2O排放总量极显著高于其他3个处理（P〈0.01）;硫包衣尿素处理的N2O排放总量显著低于尿素处理（P〈0.05）,与尿素添加双氰胺处理无显著差异（P〉0.05）。不同处理的全生命周期排放总量、单位玉米产量排放量和万元净产值排放量变化范围分别是2.56-4.11 t/（hm^2·a）、216.6-364.1 kg/t和1.15-2.19 t/万元。和传统施肥处理相比,硫包衣尿素处理可分别降低温室气体（greenhouse Gas,GHG）排放总量、单位玉米产量排放和万元净产值碳排放37.8%、40.5%和47.3%,尿素添加双氰胺处理可降低36.5%、38.6%和45.9%。化肥尤其是氮肥的生产在春玉米种植过程中对碳足迹的贡献最大,占42.4%-55.0%;玉米生产过程中的N2O排放次之,占20.8%-26.1%。在保证粮食产量和经济效益的前提下,硫包衣尿素处理和尿素添加双氰胺处理2种施肥方式具有较低的碳排放强度,可作为当地较为合理的施肥方式进行推广。

Maize production inevitably generates greenhouse gas（GHG） emissions which contribute to global warming. The greenhouse gas intensity（GHGI） of maize production was controlled by various management techniques. Fuel, fertilizer production, herbicide production, seed consumption, transportation, and on-farm energy consumption all result in GHG emissions. Life cycle assessment（LCA） methodology was adopted in this study to calculate GHG emissions under different fertilization treatments aiming at comprehensively evaluating the effects of different fertilization treatments on GHG emissions and selecting the options with both economic benefits and GHG mitigation. Four different fertilization treatments are： local traditional fertilization; urea treatment; sulfur coated urea; and urea added with dicyandiamide treatment. Static chamber and gas chromatography（GC） systems were used to continuously monitor N2 O emissions from maize cropland. N2 O emissions under different fertilization treatments were calculated. Data on the amount and type of fertilizer applied, energy consumption for the tillage, herbicide consumption, irrigation area and Diesel consumption, for tillage, electricity consumption for irrigation, and seed consumption were collected. Total GHG emissions from fertilizer production, energy consumption, seed production were estimated. GHG emission intensity based on grain yield and economic benefit were also calculated. The result showed that N2 O emissions from fertilization, total GHG emission of the whole life cycle, emission intensities based on yield and output were all ranked as local traditional fertilizationurea treatmenturea added with dicyandiamide treatmentsulfur coated urea treatment. N2 O emissions from the local traditional fertilization treatment was very significantly higher than that from the other three treatments（P〈0.01）. N2 O emissions from the sulfur coated urea treatment was significantly lower than that from the urea treatment（P〈0.05） and was not significantly different from that in the urea added with dicyandiamide treatment（P〈0.05）. Total GHG emissions from the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 4.11, 2.71, 2.56, and 2.61 t/（hm^2·a respectively. Emission per unit of yield for the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 364.1, 238.3, 216.6, and 223.4 kg/t maize, respectively. Emission per 10 000 yuan for the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 2.19, 1.32, 1.15, and 1.18 t /10 000 yuan respectively. Compared with a traditional fertilization treatment, sulfur coated urea could reduce total GHG emissions, GHG emission per unit of yield and per 10 000 yuan net output by 37.8%, 40.5%, and 47.3% respectively, while the urea added with dicyandiamide treatment could reduce total GHG emissions, GHG emission per unit of yield, and per 10 000 yuan by 36.5%, 38.6%, and 45.9% respectively. Production of fertilizers, especially nitrogen fertilizer, makes the greatest contribution to total GHG emissions for maize cultivation, accounting for 42.4%-55.0% of the total GHG emissions from the four treatments, followed by fertilizer application, accounting for 20.8%-26.1% of the total GHG emissions from the four treatments. In order to ensure grain output and economic benefits, two fertilization treatments, sulfur coated urea treatment and urea added with dicyandiamide treatment, resulted in relatively low total emissions and emission intensity. They can be recommended as options to mitigate GHG emissions from maize production.