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Studies on the solubilizing mechanisms by crops for the unavailable soil nutrients and its application to the cropping systems

作物对土壤不可利用养分的增溶机制及其在耕作系统中的应用研究

基本信息

批准号：
16580045
负责人：
MATSUMOTO Shingo
金额：
$ 2.37万
依托单位：
Shimane University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Within the Norg in soil, the available Norg is considered to be a fraction of easily mineralizable Norg. This Norg can be estimated based on the amount of released inorganic N when a soil is incubated under paddy and/or upland conditions at an appropriate temperature. However, incubation methods are time-consuming, and several methods of chemical extraction have thus been developed as substitutes for the incubation methods in many countries. The solubilization of organic nitrogen (Norg) in soil was examined by using organic acids often present in root exudates. The organic acids tested were classified into two groups depending on their solubilizing ability for Norg in a soil sample. Oxalate, malonate, tartarate, citrate and malate could dissolve Norg by increasing their concentrations, while succinate and glutarate could not dissolve Norg even when their concentrations were increased. The amount of organic N extracted with oxalate, malonate, tartarate, citrate and malate showed a strong correlation with the sum of the amounts of Al and Fe in the extracts. Therefore, it was assumed that the solubilizing ability may be attributed to the structure of these organic acids that can form stable chelate compounds with Al and Fe (oxalate, malonate, tartarate, citrate and malate). Furthermore, the amount of 20 mM citrate-extractable Norg (CEON), which was the highest among the organic acids tested, showed a strong correlation with both that of 67mM phosphate buffer, which is now being widely used as an index for estimating soil N availability in Japan, and N mineralized using an incubation method in 46 soil samples belonging to different soil types. These results suggested that CEON might be an important constituent of mineralizable Norg in soil. Therefore, organic acids secreted by crops play a role in the solubilization of available Norg surrounding the crop rhizosphere.

在土壤中的Norg中，可用的Norg被认为是容易矿化的Norg的一小部分。在适当的温度下，土壤在水田和/或旱地条件下孵育时，可以根据无机氮的释放量来估计该Norg。然而，孵育法耗时长，因此在许多国家开发了几种化学提取方法作为孵育法的替代品。利用根系分泌物中常见的有机酸，研究了土壤中有机氮（Norg）的增溶作用。所测试的有机酸根据其在土壤样品中溶解Norg的能力分为两组。草酸盐、丙二酸盐、酒石酸盐、柠檬酸盐和苹果酸盐均能随浓度的增加而溶解Norg，而琥珀酸盐和戊二酸盐则不能随浓度的增加而溶解Norg。草酸盐、丙二酸盐、酒石酸盐、柠檬酸盐和苹果酸盐提取的有机N含量与提取液中Al和Fe含量的总和有较强的相关性。因此，我们认为这种增溶能力可能归因于这些有机酸的结构，它们可以与Al和Fe形成稳定的螯合化合物（草酸盐、丙二酸盐、酒石酸盐、柠檬酸盐和苹果酸盐）。此外，20 mM柠檬酸盐可提取Norg （CEON）的量是所测有机酸中最高的，与67mM磷酸盐缓冲液（目前在日本被广泛用作估算土壤N有效性的指标）的量和46个不同土壤类型土壤样品中用孵育法矿化N的量有很强的相关性。这些结果表明，CEON可能是土壤中可矿化Norg的重要组成部分。因此，作物分泌的有机酸在作物根际周围有效氮的增溶中起作用。