控释尿素对黄河故道沙性潮土N2O排放的影响

建立田间原位试验,采用静态箱-气相色谱法,研究了常规尿素及其与硫包膜和聚氨酯包膜控释尿素配施(比例分别为30%∶70%、 50%∶50%和70%∶30%)对黄河故道沙性潮土玉米生长季氧化亚氮(N_2O)排放的影响.研究发现:常规尿素处理N_2O排放量(以N计,下同)为1.78 kg·hm~(-2),排放系数为0.38%;与之相比,配施30%、 50%和70%硫包膜尿素处理的N_2O排放量分别降低了1.12%、 22.5%和11.2%,排放系数下降2.63%～26.3%.相反,配施聚氨酯包膜尿素处理增加N_2O排放量0.02～0.41 kg·hm~(-2),其中70%聚氨酯包膜尿素处理增幅最大,达到23.0%.回归分析表明,各处理N_2O排放通量与10 cm处土温、土壤NH~+_4-N和NO~-_3-N含量呈极显著正相关(P0.01),而与土壤孔隙含水量和溶解性有机碳含量无显著关系.与常规尿素相比, 50%常规尿素+50%硫包膜控释尿素处理玉米产量略有增加,而30%常规尿素+70%硫包膜尿素处理稍微降低了玉米产量,但不显著(P0.05).因此,控释肥减缓土壤N_2O排放以及对作物产量的影响主要受控于包衣材料.

Effects of Controlled-Release Urea Application on N2O Emission in Maize-Cultivated Sandy Loam Soil

A field experiment was conducted in maize-cultivated sandy loam soil in the old flooded area of the Yellow River to evaluate the responses of N₂O emissions to application of different type of controlled-release urea. An inorganic N fertilizer was applied at 270 kg·hm^-2 during the maize season. Urea was applied alone and in combination with sulfur-coated urea (SCU) or polyurethane-coated urea (PCU) at N ratios of 30%:70%, 50%:50%, and 70%:30%, respectively. Cumulative N₂O emission under urea treatment alone (CN) was 1.78 kg·hm^-2 with a N₂O emission factor of 0.38%. In comparison to CN, 70% urea+30% SCU, 50% urea+50% SCU, and 30% urea+70% SCU treatments reduced N₂O emission by 1.12%, 22.5%, and 11.2%, respectively. In contrast, application of urea in combination with PCU (with the proportion varied from 30%-70%) increased N₂O emission by 0.02-0.41 kg·hm^-2 compared with the CN, while 30% urea+70% PCU treatment showed a 23.0% increase. Regression analysis showed that N₂O flux was significantly (P<0.01) correlated with soil temperature at 10 cm depth and concentrations of soil NH₄⁺-N and NO₃^--N in all the treatments, but not with soil moisture or dissolved organic carbon concentration. Compared with the CN, the 50% urea+50% SCU and 50% urea+50% PCU treatments slightly, but not significantly, increased the maize yield, whereas the 30% urea+70% SCU treatment showed a reduction effect. Overall, the mitigation effect of controlled-release urea on N₂O emission may primarily depend on its coating material and application rate.