水肥用量对玉米季土壤CO2排放的综合影响

为揭示水肥用量对农田生态系统土壤CO_2排放的综合影响,试验设高水W1(90 mm)、中水W0.85(76.5 mm)、低水W0.7(63 mm)这3个灌水水平,300、255、210和0 kg·hm~(-2)这4个施氮水平和90、76.5、63和0 kg·hm~(-2)这4个施磷水平,采用静态暗箱-气相色谱法对夏玉米地土壤CO_2排放进行原位观测,分析土壤CO_2排放对水肥调控的动态响应.结果表明,玉米季农田土壤CO_2排放呈双峰曲线,主峰值出现在拔节期至抽雄期,次峰出现在抽雄至灌浆期,其他阶段排放通量较低.W1在高肥F1(N 300 kg·hm~(-2),P2O590 kg·hm~(-2))和低肥F0.7(N 210 kg·hm~(-2),P2O563 kg·hm~(-2))水平下全生育期土壤CO_2平均排放通量均显著高于W0.7(P0.05);中肥F0.85(N 255 kg·hm~(-2),P2O576.5 kg·hm~(-2))和F0.7水平下,W0.85与W0.7差异不显著(P0.05).W1水平下,F1比F0.7显著增大14.82%(P0.05);W0.85水平下,F0.85比F0.7显著增大8.03%(P0.05);而W0.7水平下各施肥水平间无显著性差异.单施氮(N 210 kg·hm~(-2))或磷(P2O563 kg·hm~(-2))、氮磷配施(N 210 kg·hm~(-2)、P2O563kg·hm~(-2))较不施肥处理分别显著增加23.70%、19.00%和12.30%,且氮磷交互作用极显著(P0.01).方差分析表明,供应水平相差15%时,水肥交互作用对全生育期土壤CO_2平均排放通量影响不显著(P0.05),而对土壤CO_2累计排放量影响显著(P0.05);供应水平相差30%时水肥交互作用对全生育期土壤CO_2平均排放通量和累计排放量均影响显著(P0.05).可见,灌水量、施氮量、施磷量单因素均显著促进土壤CO_2排放,而氮磷配施起抑制作用.土壤CO_2排放与水、肥供应水平均有密切关系,水肥交互显著促进了土壤CO_2排放,通过水肥联合调控可有效调节土壤CO_2排放.

Comprehensive Effects of the Application of Water and Fertilizer Amount on CO2 Emission from Soils of Summer-maize Field

Field experiments were conducted to determine the effects of water and fertilizer amount on soil CO₂ emissions by using the method of static chamber/gas chromatography in summer maize farmland ecosystem. Three factors (three irrigation levels including 90 mm, 76.5 mm and 63 mm, four nitrogen fertilizer levels including 300 kg·hm^-2, 255 kg·hm^-2, 210 kg·hm^-2 and 0 kg·hm^-2, and four phosphate fertilizer levels including 90 kg·hm^-2, 76.5 kg·hm^-2, 63 kg·hm^-2 and 0 kg·hm^-2) were designed in the experiment. The results showed that soil CO₂ emission under different water and fertilizer conditions showed obvious seasonal fluctuation, the main and secondary peak appeared at jointing to tasseling stage and tasseling to grouting stage. The soil CO₂ emissions were relevant to the supply levels of fertilizer and irrigation. In the high fertilizer F₁ (N 300 kg·hm^-2, P₂O₅ 90 kg·hm^-2) and low fertilizer F_0.7 (N 210 kg·hm^-2, P₂O₅ 63 kg·hm^-2) conditions, average soil CO₂ emissions flux during the whole growth period of high water W₁ (90 mm) was significantly higher than that of low water W_0.7 (63 mm); the difference of soil CO₂ emissions between medium water level W_0.85 (76.5 mm) and low water level was not significant under medium and low nutrient condition F_0.85 (N 255 kg·hm^-2, P₂O₅ 76.5 kg·hm^-2). Soil CO₂ emissions intensity of high fertilizer F₁ was significantly larger (by 14.82%) than that of low fertilizer F_0.7 under high water supply W₁ (P<0.05), and that of F_0.85 was significantly bigger (by 8.03%) than that of F_0.7 in the medium water supply(P<0.05), while the difference between treatments at low water level was not significant(P>0.05). Compared with nonfertilized treatment, soil CO₂ cumulative emissions of the whole growth period with application of nitrogen fertilizer (210 kg·hm^-2), phosphate fertilizer (63 kg·hm^-2) and nitrogen mixed with phosphate fertilizer (210 kg·hm^-2, 63 kg·hm^-2) were significantly increased by 23.70%, 19.00% and 12.30%, respectively. And interaction effects between nitrogen and phosphorus fertilizer were extremely significant (P<0.01). Variance analysis of the interaction of water and fertilizer showed that the average soil CO₂ fluxes of the whole growth period were not statistically significant but cumulative emissions of soil CO₂ were significant (P<0.05) when the difference of supply level was 15%. In addition, soil CO₂ flux and cumulative emission in the whole growth period were significant when supply differed by 30%. Obviously, soil CO₂ emissions were promoted significantly by application of irrigation amount, nitrogen fertilizer, phosphorus rate and water and fertilizer interaction, while it was inhibited by nitrogen mixed with phosphorus. It was effective to regulate soil CO₂ emission by water and fertilizer controlling measures.