【摘要】 【目的】东北地区春玉米生产中过量施用氮肥的现象普遍存在,导致氮肥利用效率下降,氮素污染严重。有关施氮对东北春玉米土壤矿质氮累积特性影响的研究鲜有报道。本文利用春玉米土壤矿质氮累积量及氮代谢关键酶活性对施氮的响应行为,探寻春玉米的合理施氮量。【方法】采用田间试验和室内分析相结合的方法研究春玉米土壤矿质氮累积量及氮代谢关键酶活性对施氮的响应行为。设计6个施氮水平(N 0、60、120、180、240和300kg/hm2)。自播种开始,每隔15 d分层采集0—120 cm土样一次,共取样10次,进行相关指标的测定与计算。收获时,选择代表性的春玉米进行考种测产。【结果】春玉米产量随施氮量增加显著增加,当施氮量高于N 240 kg/hm2时,产量有减少的趋势。土壤中累积的矿质氮以硝态氮为主,其变化行为受施氮量和生育时期的双重制约。土壤硝态氮累积量随施氮量的增加和生育时期的推进均显著增加。受氮肥追施的影响,拔节大喇叭口期和抽雄期0—60 cm土层铵态氮累积量与苗期和成熟期相比显著增加;从苗期到抽雄期,0—60 cm土层的硝态氮累积量显著增加,而60 cm以下土层无规律性变化。除成熟期外,其他3个生育时期土壤硝态氮累积量均随施氮量的增加显著增加,而随着土层的加深呈降低趋势。与施氮量低的处理(无硝态氮累积峰)相比,N240和N300处理的硝态氮累积峰从拔节期的20—60 cm迁移到抽雄期的80—100 cm,说明过量施氮增加了硝态氮淋溶损失的风险,对环境形成一定的威胁。土壤脲酶和硝酸还原酶活性均随着施氮量的增加先增加后降低,均随着生育时期的推进呈波浪式变化,峰值出现在拔节期抽雄期,这与土壤中铵态氮和硝态氮累积量的变化趋势相一致。【结论】综合考虑春玉米产量性状、矿质氮累积量、氮代谢关键酶活性和经济效益,初步认为,在本试验条件下,春玉米的适宜施氮量在179 209 kg/hm2之间,且在生产上应用该施氮量可以实现氮肥用量降低、产量增加、氮肥效率提高及生态环境保护的协调一致。更多还原

【Abstract】 【Objectives】Nitrogen fertilization( N) is ubiquitously over-applied in the spring maize production in Northeast China,inducing decreased N use efficiency and serious environmental N pollution. Little information about the effects of N fertilization on soil mineral N( Nmin) accumulation characteristics has been reported in this area. The behaviors of soil Nminaccumulation characteristics and the activities of some key enzymes regulating N metabolism are affected by N fertilization. A reasonable N rate is needed for spring maize production.【Methods】Through a two-year field experiment and laboratory analysis,the behaviors of soil Nminaccumulation and theactivities of key enzymes regulating N metabolism were studied under different N fertilizer rates. Based on the survey of fertilization levels in test area,six levels of N application rates( N0,60,120,180,240 and 300 kg / ha)were designed. Soil samples were collected in 0-120 cm layer every 15 days since sowing stage,with a total of 10 samplings,and maize yield were investigated at maturity. 【Results 】The yields of spring maize increased significantly with increasing of N application rate,once the rate exceed N 240 kg / ha,the yields begin to decline.The dynamics of soil NO-3-N is influenced by both the N rates and growing stages. Because of topdressing of N fertilizer,the NH+4-N accumulation in 60 cm soil layer at the jointing to the big trumpet and tasseling stage is significantly higher than at seeding and maturity stage. The NO-3-N accumulation in 0-60 cm soil layer increases significantly from seeding to tasseling stage,and fluctuates below 60 cm soil layer. Except for maturity,NO-3-N accumulation is significantly increased with the increased N application rate,and decreased with increasing of soil depth. There is no accumulation peak appeared through the soil layer under lower N application rate,they move from 20-60 cm at jointing stage to 80- 100 cm soil layer at tasseling stage under N 240 and N 300 treatments,indicating the high NO-3-N leaching risks caused by excessive N fertilization. Both the activities of soil urease and nitrate reductase are increased with the increase of N application rate,and the highest level are at the jointing to tasseling stage,synchronized with the accumulation trend of soil ammonium N and nitrate N. 【Conclusions 】Considering comprehensively,the reasonable N application rate should be in the range of N 179-209 kg / ha under the experimental conditions. With this rate,the grain yield increase,N use efficiency and environmental safety can be synchronized realized.更多还原