减量施氮与秸秆添加对设施菜田N_2O的减排效应

Reduction of N Fertilizer and Addition of Crop Residues Can Reduce N_2O Emission in Greenhouse Field

采用静态箱–气相色谱法,在宁夏灌区设施菜田研究了不施肥(CK)、单施有机肥(M)、常规施肥(CON)、减量优化化肥(OPT)、优化化肥+调节土壤碳氮比(OPT+C/N) 5种施肥方式对春茬黄瓜和夏休闲期土壤N_2O排放通量、累积排放量和排放系数的影响。结果表明:各施肥处理土壤N_2O排放通量高峰一般出现在黄瓜滴灌施肥或夏休闲期漫灌后第1天或第3天。春茬黄瓜基肥、追肥和夏休闲期,OPT、OPT+C/N处理土壤N_2O排放通量较CON处理分别降低了3.6%～47.2%、5.9%～49.9%和14.7%～46.6%。春茬黄瓜季和夏休闲期各施肥处理的N_2O累积排放量分别为2.05～9.98kg/hm^2和3.55～7.23 kg/hm^2,OPT、OPT+C/N处理较CON处理分别降低了26.2%～34.3%和29.6%～33.7%。春茬黄瓜当季肥料的N_2O排放系数为0.43%～0.71%,而春茬黄瓜–夏休闲期总排放系数为0.54%～1.04%。N_2O总排放量与施氮量呈显著正相关(R^2=0.778);N_2O排放通量与5cm表层地温呈显著或极显著相关(R^2=0.47～0.68),与0～20cm土壤含水量呈极显著相关(R^2=0.63～0.88)。因此,相对于农民常规施氮方式,减施50%化肥氮量或减氮配合添加7.5 t/hm^2的小麦秸秆来调节土壤碳氮比都能达到设施菜田土壤N_2O的减排目标。

Using the static chamber-gas chromatograph method, a field experiment was conducted to investigate the effects of no any fertilizers (CK), single application of manure (M), conventional fertilization (CON), optimum fertilization by reduction of chemical fertilizers (OPT), and basis of OPT + regulation soil C/N ratio by addition of crop residues (OPT + C/N) on soil N2O emission flux, ratios and amounts of N2O emission during spring cucumber season and summer fallow in the Yellow River irrigation region of Ningxia. The results indicated that peaks of soil N2O emission flux under different fertilization were generally happened in the first or third days after drip fertigation in the cucumber season and flood irrigation in the summer fallow. After base fertilization, topdressing of spring cucumber and during summer fallow, soil N2O emission flux in treatments OPT and OPT + C/N were decreased by 3.6%– 47.2%, 5.9%– 49.9%, and 14.7%– 46.6% compared to treatment CON, respectively. Accumulation amounts of N2O emission under different fertilization in spring cucumber season and summer fallow were ranged from 2.05~9.98 and 3.55~7.23kg/hm^2, respectively;compared to treatment CON, those in treatments OPT and OPT + C/N were decreased by 26.2%– 34.3% and 29.6%– 33.7%, respectively. Ratios of N2O emission from application fertilizers in spring cucumber were ranged within 0.43%– 0.71%, and the total ratios of N2O emission were ranged within 0.54%- 1.04% during spring cucumber-summer fallow. Significant linear positive correlation was found between N application rate and total amount of N2O emission (R^2 = 0.778);Soil N2O emission fluxes under different fertilization treatments were significantly or extremely significantly positively correlated with 5cm of topsoil temperature (R^2 = 0.47 – 0.68), and extremely significantly positively correlated with 0 – 20cm of soil moisture (R^2= 0.63 – 0.88). Therefore, compared to the conventional application of N fertilizer by the local farmers, both reducing synthetic N fertilizer by 50% or reducing N fertilizer combined with adding 7.5 t/hm2 wheat residues to regulate soil C/N ratio could obtain the goal of reducing N2O emission in the greenhouse field.