紫云英与化学氮肥配施对双季稻田CH_4与N_2O排放的影响

Effects of combined applying Chinese milk vetch and chemical fertilizers on CH_4 and N_2O emissions from double cropping paddy fields

【目的】冬季种植紫云英翻压还田对促进稻田养分循环和提高氮素利用效率具有重要意义,本文重点研究了紫云英还田与氮肥配施对稻田温室气体排放的影响。【方法】盆栽试验条件下,设置紫云英与氮肥配施6个处理:不施肥(CK);单施尿素(CF);单施紫云英(MV);1/4紫云英+3/4尿素(1/4 MV+3/4 CF);1/2紫云英+1/2尿素(1/2 MV+1/2 CF)和3/4紫云英+1/4尿素(3/4 MV+1/4 CF),除CK外,所有处理的施氮(N)量均为111.4 mg/kg干土。采用静态暗箱–气相色谱法,监测双季稻季节内稻田CH4和N_2O排放特征及其全球增温潜势(GWP)与单位粮食产量温室气体排放强度(GHGI)。【结果】1)不同处理稻季CH4排放规律基本一致,早稻和晚稻生长季各处理CH4排放均集中在分蘖期与抽穗期,其中早稻季CH4没有明显的排放峰,其最大值为5.69mg/(m^2·h);晚稻季有两个较为明显的排放峰,出现在水稻移栽初期以及晒田期,最大峰值分别为13.33mg/(m^2·h)和8.83 mg/(m^2·h);稻田CH_4累积排放量随紫云英施用比例的增加而增加。2)不同施肥处理下N_2O排放通量有较为明显的季节变化规律。早稻季N_2O最大峰值出现在播后第3天,为1092.2μg/(m^2·h);晚稻季N_2O排放主要集中在分蘖期和后期干湿交替阶段,最大峰值为795.7μg/(m^2·h);N_2O累积排放量随紫云英施用比例的增加而减小,且MV的N_2O累积排放量为负值。3)CF处理双季稻产量最高,显著高于CK、1/4 MV+3/4CF和MV;1/2 MV+1/2 CF处理双季稻产量显著高于CK和1/4 MV+3/4 CF;各处理对稻田GWP及GHGI的影响均不显著。【结论】通过不同配比紫云英与氮肥配施盆栽试验发现,与CF相比,紫云英与氮肥不同配比对于稻田GWP及GHGI并无显著影响。

【Objectives】Winter planting of Chinese milk vetch（Astragalus sinicus L.） for returning to fields is of significance for promoting paddy nutrient cycle and improving nitrogen use efficiency. The purpose of this paper was to investigate the greenhouse gas emissions in paddy fields of Astragalus sinicus straw and nitrogen fertilizers.【Methods】A pot experiment was conducted, and there were 6 Chinese milk vetch and fertilizer treatments, no fertilizer（CK）, single urea（CF）, single application of Chinese milk vetch（MV）, 1/4 Chinese milk vetch ＋ 3/4 urea（1/4 MV ＋ 3/4 CF）, 1/2 Chinese milk vetch ＋1/2 urea（1/2 MV ＋ 1/2 CF） and 3/4 Chinese milk vetch ＋1/4 urea（3/4 MV ＋1/4 CF）. Except for the CK, the nitrogen rate of other treatments was 111.4 mg/kg dry soil.Chromatographic determination of CH4 and N2O emission characteristics in double cropping rice season paddy field, global warming potential（GWP） and greenhouse gas emissions intensity per unit grain yield（GHGI） were measured using the static chamber gas method.【Results】1） The CH4 emission in different rice seasons was basically consistent in early rice and late rice growing seasons, and the CH4 emissions were concentrated in the tillering stage and the heading stage of early rice and late rice. The early rice season CH4 emission has no obvious emission peak, with the maximum value of 5.69 mg/（m^2·h）, and the late rice season emission had two obvious emission peaks, appeared at the early rice transplanting and field drying, with the maximum peak values of 13.33 mg/（m^2·h） and 8.83 mg/（m^2·h）. The cumulative CH4 emission was increased with the increase of milk vetch ratio.2） Under different fertilization treatments, the N2O emission flux had obvious seasonal variation pattern. The maximum peak value of N2O at the early season appeared in the third day after the sowing, and was 1092.2μg/（m^2·h）. The late rice season N2O emissions mainly concentrated in the tillering stage and the late stage of alternative drying and wetting, with the peak value of 795.7 μg/（m^2·h）, the cumulative N2O emission was decreased with the increase of the with milk vetch ratio, and the N2O cumulative emission of MV was negative. 3）The double rice total yield of the CF treatment was the highest, and significantly higher than those of the CK, 1/4 MV＋3/4 CF and MV, and the double rice total yield of the 1/2 MV＋1/2 CF was significantly higher than those of the CK and 1/4 MV＋3/4 CF. The effects of treatments on GWP and GHGI in paddy fields were not significant.【Conclusions】Compared with the CF, different ratios of Chinese milk vetch and nitrogen fertilizer had no significant effects on GWP and GHGI in paddy fields.