有机、无机氮肥施用对苜蓿产量、土壤硝态氮和温室气体排放的影响

2012年5月—2014年6月,采用田间小区试验方法,研究了不同氮肥管理对N₂O与CH₄的排放、土壤硝态氮含量以及苜蓿干草产量的影响.试验共设5个处理:对照(CK)、单施尿素处理(100 kg N·hm^-2, CF)、尿素(100 kg N·hm^-2)与腐熟牛粪(60 kg N·hm^-2)混施处理(DM₁)、尿素(100 kg N·hm^-2)与沼液(60 kg N·hm^-2)混施处理(DT)及减量尿素(40 kg N·hm^-2)与牛粪(60 kg N·hm^-2)混施处理(DM₂).结果表明: 与CK相比,CF、DM₁、DT和DM₂处理苜蓿干草产量分别增加44.2%、38.9%、56.3%和30.6%,N₂O排放分别比对照增加52.2%、89.1%、133.7%和59.4%,但各施肥处理对甲烷吸收表现出不同程度的抑制作用.苜蓿生产中,尿素和牛粪处理N₂O-N排放与肥料氮素投入量比值(排放系数)为0.25%～0.28%,而沼液处理N₂O-N排放系数为0.64%,显著高于前者.苜蓿生产中,施用化肥或有机无机混施均能显著增加苜蓿干物质产量,土壤硝态氮深层淋洗风险较小,但增加了CO_2-equivalent净排放量.

Impacts of organic and inorganic fertilizations on alfalfa yield,soil nitrate and greenhouse gas emissions

Field plot experiment was carried out during May 2012 to June 2014 to investigate the impacts of nitrogen fertilizations on the emissions of nitrous oxide (N₂O) and methane (CH₄) from alfalfa field as well as the dry matter yield and soil nitrate contents. Five treatments including CK, urea (100 kg N·hm^-2, CF), urea (100 kg N·hm^-2) + dairy cattle manure (60 kg N·hm^-2) (DM₁), urea (100 kg N·hm^-2)+ digestate (60 kg N·hm^-2) (DT) and reduced urea (40 kg N·hm^-2)+ dairy cattle manure (60 kg N·hm^-2) (DM₂) were conducted. Results indicated that in comparison with CK, CF, DM₁, DT and DM₂ treatments significantly increased the dry matter yields of alfalfa by 44.2%, 38.9%, 56.3% and 30.6%, and increased the N₂O emissions by 52.2%,89.1%, 133.7% and 59.4%, respectively, whereas the oxidation of atmospheric CH₄ was reduced to different extents by these N management practices. The losses of N₂O-N originated from urea and dairy cattle manure N accounted for 0.25%-0.28% of their inputs, whereas a greater va-lue of 0.64% was observed for digestate N. Applying urea or organic N to alfalfa field could significantly increase the dry matter yield without significant NO₃^--N leaching, however, it would lead to higher net CO_2-equivalent emissions of producing 1 t dry matter of alfalfa.