节水灌溉、树脂包膜尿素和脲酶/硝化抑制剂对双季稻温室气体减排的协同作用

【目的】研究薄浅湿晒节水灌溉技术的减排增产效果及其与新型氮肥和添加剂的协同作用,提出增产与减排双赢的水氮管理措施。【方法】以江汉平原双季稻为研究对象,设置4种不同水氮管理措施:1普通尿素+常规灌溉(U+CI),作为对照(CK);2普通尿素+薄浅湿晒节水灌溉(U+SI);3树脂包膜控释尿素+薄浅湿晒节水灌溉(CRU+SI);4碧晶尿素(含0.5%硝化抑制剂2-氯-6-三氯甲基吡啶)+氢醌+薄浅湿晒节水灌溉(NU+HQ+SI)。采用静态箱-气象色谱法进行稻田温室气体连续监测,分析不同水氮管理措施的CH_4和N_2O排放量、基于CH_4和N_2O的综合温室效应。水稻收获后统计产量,计算各处理单位产量的排放量(GHGI)。【结果】薄浅湿晒节水灌溉有效抑制了特别是水稻生育后期的CH_4排放峰,导致早稻和晚稻U+SI处理的CH_4排放量极显著地小于U+CI处理(P0.01),且晚稻的减排幅度更大。节水灌溉条件下,施用树脂包膜控释尿素、碧晶尿素混施氢醌比普通尿素进一步减少CH_4排放量,CRU+SI和NU+HQ+SI处理的两季水稻CH_4排放总量分别是U+SI处理的60%和73%。薄浅湿晒节水灌溉促进了稻田N_2O的排放,早稻和晚稻U+SI处理的N_2O排放量分别比U+CI处理显著增加了34%和39%(P0.05)。节水灌溉条件下,相比普通尿素,碧晶尿素混施氢醌、树脂包膜控释尿素处理的N_2O排放量呈现减少的趋势,尤其以碧晶尿素混施氢醌处理的控制效果更好。综合早稻和晚稻2个季节,薄浅湿晒节水灌溉下CH_4和N_2O排放此消彼长,但CH_4减排量大于N_2O增排量。总体而言,薄浅湿晒节水灌溉具有减少稻田综合温室效应的作用,减排效果视不同氮肥种类而不同,以树脂包膜控释尿素的减排效果最高为49%,其次为碧晶尿素混施氢醌,减排幅度达46%,普通尿素最低为28%。同时,施用树脂包膜控释尿素、碧晶尿素混施氢醌更有利于增加水稻产量,降低排放强度。【结论】薄浅湿晒节水灌溉具有减排稳产的良好效果,薄浅湿晒节水灌溉结合施用树脂包膜控释尿素和添加脲酶/硝化抑制剂能进一步增加水稻产量和减少稻田温室气体排放,可作为水稻生产减排增效的推广技术。

Synergistic Effects of Water-Saving Irrigation,Polymer-Coated Nitrogen Fertilizer and Urease/Nitrification Inhibitor on Mitigation of Greenhouse Gas Emissions from the Double Rice Cropping System

【Objective】Optimization of water and nitrogen management measures has a great significance for rice yield improvement and greenhouse gas emission reduction in paddy fields. To establish water and fertilization management regimes with effects on yield promotion and greenhouse gas mitigation, a new water-saving irrigation technique, “thin and shallow alternate wetting drying”, was investigated in the double rice cropping system. Synergistic effects of water-saving irrigation and new types of nitrogen fertilizer on rice yield and greenhouse gas emissions were evaluated. 【Method】The study focused on double rice cropping system in the Jianghan Plain, Hubei province, Central China. Greenhouse gas emissions were observed from four different treatments: U＋CI: urea with conventional traditional irrigation, as the control (CK); U＋SI: urea with “thin and shallow alternate wetting drying” water-saving irrigation; CRU＋SI: polymer-coated urea with “thin and shallow alternate wetting drying” water-saving irrigation; NU＋HQ＋SI: nitrapyrin crystal urea with hydroquinone and “thin and shallow alternate wetting drying” water-saving irrigation. Measurements were taken using the automatic static chamber-GC (gas chromatography) method. CH₄ and N₂O emissions, and total CO₂-eq (CH₄＋N₂O, on a 100a horizon) of each treatment were analyzed. Rice yield per plot and greenhouse gas intensity (GHGI) were calculated after harvesting. 【Result】The “thin and shallow alternate wetting drying” water-saving irrigation technique diminished CH₄ emission fluxes during the early and late rice seasons, especially at the reproductive stage, resulted in lower CH₄ emissions for U＋SI compared to U＋CI (P<0.01). The reduction in CH₄ emissions in the late rice season was greater than in the early rice season. By using water-saving irrigation techniques, pronounced differences in CH₄ emissions were identified among polymer-coated urea, nitrapyrin crystal urea with hydroquinone and urea treatments. Total CH₄ emissions during two rice seasons from CRU＋SI and NU＋HQ＋SI were 60% and 73% of emissions from the U＋SI treatment, respectively. “Thin and shallow alternate wetting drying” water-saving irrigation increased N₂O emissions in paddy fields. Compared to U＋CI, the U＋SI treatment significantly increased N₂O emissions in the early and late rice seasons by 34% and 39%, respectively (P<0.05). Compared to urea, N₂O emissions from nitrapyrin crystal urea with hydroquinone and polymer-coated urea treatments were decreased. The effect of nitrapyrin crystal urea with hydroquinone on the control of N₂O emissions was superior to that of the other two nitrogen fertilizers. A trade-off was identified between CH₄ and N₂O emissions under “thin and shallow alternate wetting drying” irrigation, but the effect on the reduction of CH₄ emissions was greater than the increase in N₂O emissions. Overall, “thin and shallow alternate wetting drying” irrigation can reduce total greenhouse gas emissions, with the strength of the mitigation effect depending on the type of nitrogen fertilizer used. Polymer-coated urea had the greatest mitigation effect, reducing total CO_2-eq emissions by 49%, followed by nitrapyrin crystal urea with hydroquinone (46%) and urea (28%). Furthermore, polymer-coated urea and nitrapyrin crystal urea with hydroquinone were more beneficial for rice yield promotion and decreased greenhouse gas intensity of rice production. 【Conclusion】The results suggest that “thin and shallow alternate wetting drying” water-saving irrigation has good effects on yield maintenance and GHG abatement. The combined application of water-saving irrigation and polymer-coated urea or nitrapyrin crystal urea with hydroquinone could further increase rice yield and reduce greenhouse gas emissions. Thus, these water and nitrogen management measures deserved wider extension in order to simultaneously increase grain yield and decrease global warming effects.