作 者 ：姜慧敏,李树山,张建峰,杨俊诚,李玲玲,张水勤,郭俊娒,刘恋,谢义琴,王峰源
期 刊 ：植物营养与肥料学报 2014年 20卷 6期 页码：1421-1430
Keywords:15Nlabeled, soilorganicNfraction, transformationandrelationship,
摘 要 ：【目的】本研究旨在探明外源化肥氮在土壤不同有机氮库中的动态转化及关系,为实现化肥氮素养分高效利用的有效调控提供理论依据。【方法】利用15N示踪技术(15N标记尿素,丰度10.3%),以江西红壤性水稻土为研究对象,通过土壤培养试验,研究农民习惯施肥水平下,水稻不同生育期外源化肥氮在土壤有机氮库(氨基酸态氮、 氨基糖态氮、 酸解铵态氮、 酸解未知氮和非酸解有机氮)中的转化及关系。采用通径分析方法,评估来自外源化肥氮的有机氮各组分之间的转化关系。【结果】 1)土壤中氨基酸态氮和氨基糖态氮中来自外源的化肥氮(氨基酸态氮-15N和氨基糖态氮-15N)含量从分蘖期到拔节期显著升高(P<0.05),从拔节期到灌浆期显著降低(P<0.05),全生育期两个组分中来自外源化肥氮的含量最高值分别为26.5和8.4 mg/kg,均出现在分蘖期和拔节期之间;酸解性铵态氮中来自外源的化肥氮(酸解性铵态氮-15N)含量从分蘖期到成熟期逐渐降低,全生育期的动态转化符合指数递减方程;酸解未知态氮中来自外源的化肥氮(酸解未知态氮-15N)含量随着生育期的延长逐渐达到动态平衡,最大值接近12.8 mg/kg;非酸解性有机氮中来自外源的化肥氮(非酸解性有机氮-15N)含量在全生育期的变化符合对称方程,最低值7.9 mg/kg出现在拔节期和灌浆期之间。2)在水稻营养生长阶段的分蘖期和拔节期,外源化肥氮分别以酸解性铵态氮和氨基酸态氮为主要方式结合到土壤有机氮库中,其含量分别占施入化肥氮的21.5%和14.8%;在水稻营养生长和生殖生长并进阶段(灌浆期)和生殖生长阶段(成熟期),外源化肥氮主要结合到非酸解性有机氮库中,分别占施入化肥氮的8.7%和12.7%。3)土壤各有机氮库中来自外源的化肥氮之间存在相互转化的关系,酸解性铵态氮库起到了“暂时库”的作用,生育前期在土壤中固持氮,当可利用性氮受限时,又可以作为有效氮库释放氮供作物吸收;在整个生长期中氨基酸态氮库对外源化肥氮的转化积累起到了“过渡库”的作用,固持在氨基酸中的化肥氮可以转化成酸解性铵态氮和氨基糖态氮。4)灌浆期和成熟期植物吸收的来自外源的化肥氮与氨基酸态氮-15N和酸解铵态氮-15N的关系更密切。【结论】外源化肥氮在土壤中转化的过程中酸解性铵态氮起到了“暂时库”的作用,氨基酸态氮起到了“过渡库”的作用,非酸解性有机氮可作为氮素的“稳定库”存在,外源氮在这几个主要的氮库中动态转换以保持土壤-作物体系中氮素的循环。
Abstract:【Objectives】 In this study, the transformation and relationship of external chemical N in soil organic nitrogen (SON) fractions were determined during one growing season of rice in order to provide a theoretical basis for reasonable fertilizer application and the effective adjustment to N fertilizer. 【Methods】 A pot experiment was carried out on a subtropical paddy soil in Jiangxi province, and a total N 180.0 kg/ha (15N labeled urea, atom 10.3%) was applied to a rice crop during one growing season under the conventional farmer practices. Distribution and dynamics of the chemical N fertilizer in different SON fractions (i.e., amino acid N, amino sugar N, hydrolysable ammonium N, hydrolyzable unknown N and acid insoluble N) were measured. Path analysis was used to evaluate the transformation process between SON derived from the fertilizer in soil-plant system.【Results】 1) The accumulation of fertilizer-derived N in different SON fractions was season-specific. The recovery contents of the fertilizer-derived N in soil amino acid N and amino sugar N at the jointing stage are significantly higher than those at the tillering stage (P<0.05). The enrichments of 15N are significantly declined from the jointing stage to filling stage (P<0.05). The dynamics of enrichment of 15N in soil amino acid N and amino sugar N during the growing season can be fitted as a Gauss equation, the maximum contents are 26.5 and 8.4 mg/kg, respectively, which are found between the tillering stage and jointing stage. The enrichment of 15N in hydrolysable ammonium N is declined gradually from the tillering stage to harvest stage, and the dynamics of the enrichment of 15N in soil hydrolysable ammonium N could be expressed as an exponential decline equation. The enrichment of 15N in hydrolyzable unknown N is gradually in a dynamical equilibrium from the tillering stage to harvest stage, and the dynamics of the enrichment of 15N in soil hydrolysable unknown N can be fitted as an exponential equation. The enrichment of 15N in acid insoluble N can be fitted as a symmetry equation, and the minimum of the enrichment of 15N is 7.9 mg/kg, which is found between the jointing stage and filling stage. 2) At the tillering stage and jointing stage of rice, preferential enrichment of 15N is found in soil hydrolysable ammonium N and amino acid N, accounting for 21.5% and 14.8% of the total N of the chemical N fertilizer, respectively. The accumulation of residual fertilizer-derived N in acid insoluble N is higher at the filling and harvest stages, accounting for 8.7% and 12.7% of the total N of the chemical N fertilizer, respectively. 3) The path analysis indicates that the hydrolysable ammonium N is a temporary pool for rapid chemical N fertilizer retention and is apt to release N for crop uptake simultaneously. In contrast, the amino acid N could serve as a transitional pool of available N in soil system through transferring into hydrolysable ammonium N and amino sugar N. 4) The fertilizer-derived N in hydrolysable ammonium N and amino acid N are closely related to fertilizer-derived N in crop uptake. 【Conclusions】 In a plant-soil system, the fertilizer N cycling during a growing season is closely related to temporal patterns of fertilizer N transformation into different SON fractions. The fertilizer-derived N can be derived into three pools with different availabilities. The hydrolysable ammonium N fraction can serve as a temporary pool containing readily available N to be released fast, while the amino acid N can be considered as a transitional pool for the transformation of the hydrolysable ammonium N and amino sugar N, and the acid insoluble N is tightly associated with fertilizer N stabilization. Importantly, there is an interim shift among the three substantial N pools to maintain soil N cycling and supply in a soil-plant system.
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