甘肃河西绿洲灌区盐渍化环境加重玉米缺锌的机理研究

Zn-deficiency of maize is very general in salt-affected soil in Hexi Oasis irrigation area of Gansu, but it differs in different typical saline soil. There are two main situations, the one is zinc is still deficient while the content of soil available zinc is higher than the Zn-deficiency critical value, the other is application of zinc fertilizer is ineffective in the low content of soil available zinc. Project applicants consider it is possible that soil salinity and its ions involves in the transformation and transportation of Zn Speciation in Soil, reduces the content of active zinc in soil and inhibits maize on the absorption of zinc. The project takes different typical salt-affected soil as the research object, adopting the method of combining the field investigation, pot experiment and analysis indoor, studies the distribution characteristics of Zn Speciation and the contribution of available zinc in salt-affected soil, and effects of soil salinity on transformation and availability of soil zinc and exogenous zinc, and rules of maize on soil available zinc transportation from roots to the grand parts on salt stress, to find out mechanisms of maize on aggravating Zn-deficiency in salt-affected soil in Oasis area. This project breaks the limitation that a single ion affects crop Zn-deficiency, pays more attention to the overall impact of salinization environment, is expected to get a breakthrough of the other nonspecial ions on influence Zn-deficiency of maize. Research results have not only scientific significance on enhancing soil-plant zinc nutrition theory, but also important guidance on reasonable supply of zinc fertilizer in salt-affected soil in Hexi Oasis irrigation area of Gansu.

甘肃河西绿洲灌区盐渍化土壤上玉米缺锌现象非常普遍，但不同类型盐渍土上的缺锌情况不同，主要表现为有效锌含量高于缺锌临界值仍缺锌和有效锌含量虽低但施用锌肥无效两种。项目申请者认为，可能是土壤盐分及其离子参与了锌形态转化和转运，降低了土壤中活性锌含量、抑制了玉米对锌的吸收。本项目采用野外调查、盆栽试验和室内分析相结合的方法，以不同类型盐渍化耕地土壤为研究对象，进行盐渍化土壤中锌形态分布特征及其对有效锌的贡献、土壤盐分对土壤锌和外源锌形态转化及有效性的影响、盐分胁迫下土壤有效锌从玉米根系向地上部转运的规律研究，旨在揭示河西绿洲灌区盐渍化环境加重玉米缺锌的机理。本项目突破了单一离子影响作物缺锌研究的局限，更注重盐渍化环境的总体影响，有望在其它非专性离子影响玉米缺锌方面取得突破。研究成果不仅对丰富土壤-植物锌营养理论有重要科学意义，而且对绿洲灌区盐渍化土壤上合理施用锌肥也有重要指导作用。

甘肃河西绿洲灌区玉米缺锌症状非常普遍，而且不同类型、不同程度盐渍化土壤中有效锌含量和植株缺锌率的差异也较大。针对这一现象，我们以甘肃省河西绿洲灌区不同类型盐渍化耕地土壤为研究对象，采用典型调查取样、盆栽试验、室内分析相结合的方法，深入探讨了绿洲灌区盐渍化环境加重玉米缺锌的机理。主要得到以下结论：①研究区土壤中的有效锌含量介于0.289～0.736mg.kg-1之间，平均为0.473 mg.kg-1。土壤有效锌含量与HCO3-、Mg2+、Na+含量呈极显著负相关，与Cl-、Ca2+、K+含量呈显著负相关，与SO42-含量之间的相关性不显著。②Mg2+对土壤有效锌含量表现出强烈的直接和间接负效应，HCO3-表现出很大的直接负效应和强烈的间接正效应，Cl-、K+和Na+对土壤有效锌含量均表现出较强的直接和间接负效应，SO42-表现出较弱的直接和间接正效应，Ca2+表现出较弱的直接和间接负效应。Mg2+、HCO3-和Na+通过直接作用和间接作用成为影响土壤有效锌含量变化的三个主导因素，对决定系数R2的贡献超过了68%；③RES-Zn是绿洲盐化潮土区最主要的锌形态，占到了全锌含量的79.43%；其次是COFe-Zn，占12.05%；第三是AOFe-Zn，占5.21%；第四是WBO-Zn，占1.23%；土壤中DTPA-Zn与CAB-Zn和OxMn-Zn含量呈显著正相关，与Ex-Zn、WBO-Zn、SBO-Zn、COFe-Zn、Total-Zn含量呈正相关关系，与AOFe-Zn、RES-Zn含量呈负相关关系。④绿洲盐化潮土上的玉米缺锌问题与土壤含镁量水平密切相关，随着施镁量的增加，玉米幼苗的生长受到抑制，达到515 mg/kg时表现出明显的镁中毒症状和典型缺锌症状，株高、干重、叶片中的叶绿素含量和SOD、POD、CAT活性都显著降低，MDA含量显著增加。施镁抑制了玉米幼苗对锌的吸收，但对茎叶的抑制程度明显高于根系，导致玉米根系的锌含量和吸收量都普遍高于茎叶，锌从根系向地上部的转运率显著降低；施镁降低了土壤有效锌含量，用量达到515 mg/kg时，土壤有效锌含量已超过了土壤缺锌临界值。本研究结果不仅对丰富植物锌营养学理论具有重要的科学意义，而且对于盐渍土上锌肥的合理施用，并使盐渍土在施用锌肥中得到改良有重要的指导作用。