不同管理方式对夏玉米氮素吸收、分配及去向的影响

【目的】本文利用15N同位素示踪技术探讨传统(CT)和优化(YH)两种管理方式对夏玉米氮素吸收、分配及去向的影响。分析目标产量下化肥氮的变化,解析夏玉米花前、花后氮素利用及转移规律,探讨肥料氮、土壤氮与作物氮之间的关系,为该地区夏玉米的科学合理施氮提供合理依据。【方法】在传统和优化两种管理方式定位试验中设置15N微区,采用将15N标记的尿素表施的方法,分析植株和土壤样品。新鲜土壤用1 mol/L KCl浸提,滤液用TRACCS 2000型流动分析仪测定土壤的NH+4-N和NO-3-N含量。15N标记的土壤和植物全氮的测定用烘干样(过0.15 mm筛),然后用美国THERMO finnigan公司生产的稳定同位素质谱仪DeltaplusXP进行测定。【结果】在该试验条件下,优化方式下夏玉米籽粒产量和总吸氮量显著高于传统方式,分别增加12%和10%。作物收获后,优化方式的15N吸收量及利用率显著高于传统方式,利用率分别为20.81%、32.54%。夏玉米各器官中氮素的积累量和向籽粒中的转移量土壤氮显著高于肥料氮,传统方式籽粒中氮素的57.73%、优化方式籽粒中氮素的45.15%来自各器官的转移,近一半的氮素是在花后积累的,基施高氮对作物生长作用不大。开花期土壤表层硝态氮含量传统方式显著高于优化方式,收获后有所降低,而土壤深层含量明显增加,有向下淋洗的趋势。夏玉米收获后,传统方式各土层的原子百分超均高于优化方式,而且在20—40 cm处出现了明显的15N累积峰,与开花期相比,40 cm以下土层的原子百分超明显增大,氮肥随水向下淋洗强烈。夏玉米收获后传统方式土壤氮素残留率高达56.18%,表现为土壤残留损失作物吸收;优化方式则表现为土壤残留作物吸收损失。【结论】在优化方式中夏玉米施氮量为N 185 kg/hm2时,玉米达到高产水平且氮肥的利用率高。适当减少施氮量及增加后期追肥次数可实现夏玉米的高产和肥料的高效利用。

Effects of different management patterns on uptake,distribution and fate of nitrogen in summer maize

【Objectives】 A field experiment was conducted to determine effects of different management patterns on uptake, distribution and fate of nitrogen in summer maize. We indicated impacts of optimizing management pattern on“N uptake-soil residues-loss”, explored nitrogen accumulation and transport at the anthesis and maturity stages, and identified fate of nitrogen. The study can provide theoretical and technical supports for local agricultural development. 【Methods】 Two management patterns i.e., conventional pattern (CT) and optimized pattern (YH) in nitrogen and water management] were designed through establishing ¹⁵N-micropolt experiments in the field. We analyzed characteristics and nitrogen utilization by measuring the soil and plant samples. Soil samples were extracted with 1 mol/L KCl, and analyzed for NH⁺₄-N and NO^-₃-N using continuous flow analysis (TRAACS 2000) in laboratory. The samples were dried and sieved through a 0.15 mm mesh. They were taken for determination of ¹⁵N using the Delta ^plusXP. 【Results】The differences of grain yield and total nitrogen uptake between the optimized and conventional patterns are significant. As to the conventional pattern, the grain yield and nitrogen uptake are 12% and 10% lower than those of the optimized patterns, respectively. The rate of ¹⁵N utilization of the conventional patterns (20.81%) is significantly lower than that of the optimized patterns (32.54%). The contents of accumulated nitrogen in the crop aboveground organs and the contents of transferred nitrogen to the grain of soil nitrogen are significantly higher than those of fertilizer nitrogen. About half of nitrogen content in seed comes from the accumulation after the flowering. The transport contribution rates by organs of the conventional and optimized patterns are 57.73% and 45.15%, respectively. The nitrate and marked ¹⁵N accumulation amounts in the soil surface at the period of the anthesis under the conventional patterns are higher than those under the optimized patterns, and after the harvest the ¹⁵N content of the conventional pattern with soil depth is increased for the first and then decreased, with the accumulation peak in 20-40 cm. The residual nitrogen rate in soil of the conventional pattern is up to 56.18%. The fate of nitrogen fertilizer is as follows: soil residual> loss > crop uptake. As to the optimized treatment, the fate of nitrogen fertilizer is as follows: soil residual> crop uptake > loss. 【Conclusions】It can be reached high level of grain yield and efficiency of nitrogen with nitrogen controlled at around 185 kg/ha. Thus, less nitrogen and more times of fertilization at late growth stage not only raise the efficiency of nitrogen fertilizer but also increase food production.