不同灌溉施肥措施对夏玉米-冬小麦农田N2O排放和产量的影响

为明确不同灌溉施肥措施下夏玉米-冬小麦轮作农田N_2O的排放特征,寻求既能减少N_2O排放又保证粮食产量的灌溉施肥方法,以华北地区夏玉米-冬小麦轮作农田为研究对象,利用静态暗箱-气相色谱法对土壤N_2O排放特征进行了周年(2015年6月15日-2016年6月12日)观测,探讨了常规施氮量(夏玉米:205.5 kg/hm2;冬小麦:250 kg/hm2)下传统灌溉施肥(FP100%)、滴灌+传统施肥(DN100%)、滴灌水肥一体化(FN100%)以及滴灌水肥一体化下不同施氮量(减氮60%(FN40%)、减氮30%(FN70%)、常规氮量(FN100%)和增氮30%(FN130%))下农田N_2O排放特征及土壤温湿度对农田N_2O排放的影响,另设滴灌+不施氮肥(CK)为对照。结果表明:在夏玉米-冬小麦轮作体系中小麦季农田土壤N_2O排放通量高于玉米季,夏玉米季土壤N_2O阶段排放峰值出现在拔节期和抽雄期;而冬小麦季土壤N_2O阶段排放峰值出现在冬前苗期和拔节期。与FP100%处理相比,FN40%处理在夏玉米和冬小麦季的N_2O平均排放通量分别降低了70.8%和66.7%,N_2O排放总量分别减少了58.7%和66.3%;整个轮作季周年产量没有显著减少,N_2O排放总量显著降低了62.9%(P0.05)。FN40%处理夏玉米季和冬小麦N_2O排放系数分别为0.06和0.01,显著低于其他施肥处理(P0.05)。土壤温湿度均影响农田N_2O排放,但不同处理在夏玉米和冬小麦生长季与土壤温度和土壤湿度的相关性并不相同。综合考虑N_2O排放量和作物产量,研究认为,在华北地区夏玉米-冬小麦轮作系统下,若采用滴灌,则根据作物需肥规律同时采用水肥一体化方式进行施肥才既有增产,又减少农田N_2O排放的效果,并且在滴灌水肥一体化技术下,减少60%施氮量在保障粮食产量的同时,可以有效地减少N_2O排放,是兼顾作物产量及大气环境的推荐管理措施。

Effect of different irrigation and fertilization managements on N2O emissions and yeild in summer maize-winter wheat field

Abstract: A winter wheat-summer maize cropping system has been the dominant system on the North China Plain (NCP) during the past three decades, accounting for approximately 50% of wheat production and 35% of maize production in China. Nitrogen (N) supplied through fertilization is one of the main plant nutrients affecting plant growth and plays a powerful role in the promotion of crop production. Traditional N application rates adopted by farmers to achieve high crop production range from 550 to 600 kg/hm2 for the winter wheat-summer maize cropping system in this region, which exceeds the crop N requirement. Furthermore, 50%-80% of the fertilizer is applied at planting. The application of excess inorganic N fertilizer, the broadcasting of N on the soil surface in a few split applications and flooding irrigation on the NCP have resulted in not only a low nitrogen use efficiency, but also a series of environmental problems, such as gaseous N losses.Drip fertigation is an effective approach for improving fertilizer use efficiency, as well as ecological environment. One-year experiment (from June 15, 2015 to June 12, 2016) at a summer maize-winter wheat field in NCP was performed to quantify N2O emissions from maize and wheat fields and evaluate N2O mitigation efficiency of alternative irrigation and fertilization managements by using the static opaque chamber method. We measured N2O emissions under 5 treatments, including no N fertilizer use (CK), drip irrigation + N broadcasting (DN100%), fertigation (FN100%), fertigation with N reduced by 60% (FN40%) and farmers'' traditional practice (FP100%). The cumulative N2O emission in wheat field was higher than that in maize field. The N2O peaks of maize were observed in jointing and tasseling stage, while that of wheat were observed in seedling and jointing stage. Compared with FP, the average N2O flux under the FN40% treatment was reduced by 70.8% and 66.7% and the cumulative N2O emissions by 58.7% and 66.3% in maize and wheat season, respectively; in addition,the annual cumulative N2O emissions were decreased by 62.9% and a stable grain yield was maintained. The emission factors under FN40% treatment were 0.06 and 0.01 for maize and wheat, respectively, which were significantly lower than other fertilization treatments. Both soil temperature and soil moisture could influence the N2O emissions in this study. However, there were different correlations in the different managements. This research indicates that N fertigation rates in a wheat-maize cropping system can be significantly reduced by 60% compared to FP100%, without negatively affecting grain yield, but decreasing N2O emissions.