不同水氮耦合管理下耕层土壤的氮动态

以中国科学院封丘农业生态试验站水氮耦合长期试验地为研究平台,采集了不同水氮耦合管理下耕层0～10 cm、10 ～ 20 cm和0～20 cm土壤,测定了六种形态的氮(无机氮、有机氮、酸解有机氮、酸解铵态氮、溶解性有机氮和微生物生物量氮)和三种与氮周转密切相关的生物性指标(脲酶活性、蛋白酶活性和硝化势).三因素方差分析结果表明,施氮和耕层深度对六种形态氮均有显著作用,而灌水对这六种形态氮无显著作用.单因素方差分析结果显示施氮明显提高了耕层0 ～ 20 cm土壤无机氮、有机氮、脲酶活性及硝化势,而对土壤酸解有机氮和酸解铵态氮无显著影响;六种形态的氮、蛋白酶活性及硝化势均不受灌水量的影响.不同水氮耦合管理下耕层0 ～ 10 cm土壤六种形态氮、脲酶活性、蛋白酶活性及硝化势几乎均明显地高于10～20 cm土壤.通过对不同水氮耦合管理下耕层土壤氮动态的研究,本研究得出最佳的水氮耦合管理模式是灌水至20 cm土层的田间持水量和每季施氮190 kg hm-2.

Dynamics of nitrogen in topsoil related to integrated water and nitrogen management

From the fields of a long-term (since 2005) experiment on integrated water and nitrogen management in Fengqiu National Agro-ecological Experiment Station, samples were taken of the soils in the cultivated layers (0~10 cm, 10~20 cm and 0~20 cm) of fields under different patterns of integrated water and nitrogen management after the harvest of summer maize in September, 2011 for analysis of six forms of nitrogen, i.e. inorganic nitrogen (IN), organic nitrogen (ON), dissolved organic nitrogen (DON), acidolytic organic nitrogen (AON), acidolytic ammonium nitrogen (AAN), microbial biomass nitrogen (MBN), and three biological indices that are closely related to N turnover, i.e. urease activity (URE), Protease activity (PRO) and nitrification potential (NP). Three-way ANOVA of the analytic results indicate that both nitrogen fertilization and topsoil depth had significant effects on the six forms of nitrogen, but irrigation had none. One-way ANOVA shows that nitrogen fertilization significantly increased soil IN, ON, URE and NP in the 0~20 cm topsoil, but had no such effect on soil AON and AAN and volume of irrigation had nothing to do with the six forms of nitrogen, PRO and NP. Regardless of patterns of integrated water and nitrogen management, the six forms of nitrogen, URE, PRO and NP were almost all considerably higher in the 0~10 cm topsoil than in the 10~20 cm topsoil. Through the experiment, it is found that irrigation to meet the field water-holding capacity in the 0~20 cm soil layer and nitrogen fertilization at a rate of 190 kg N hm-2 per crop season is the optimal patterns of integrated water and nitrogen management.