不同水平氮添加下华北盐渍化草地根际土壤阴阳离子特征

Characteristics of anion and cation in rhizosphere soil of saline grassland in North China under different nitrogen addition levels

以华北农牧交错带重度盐渍化赖草草地为对象,研究不同水平氮处理(0、1、2、4、8、16、24、32 g N·m^(-2)·a^(-1))下根际土壤、非根际土壤以及根际与非根际混合土壤的阴阳离子含量,分析外源氮输入影响盐渍化草地土壤理化特征的过程及机理。结果表明:随着氮添加量的增加,根际、混合和非根际土壤的pH值均显著降低,与对照相比,32 g N·m^(-2)·a^(-1)处理下3种土壤pH值分别下降1.2、0.9和0.6,根际土壤的pH值比非根际土壤降低0.44。根际、混合和非根际土壤的Na+含量显著降低,NO_(3)^(-)含量显著升高。与对照相比,32 g N·m^(-2)·a^(-1)处理下根际土壤Na+含量占可溶性总盐含量的比例减少14%,非根际土壤减少12%,而根际土壤的NO_(3)^(-)含量占可溶性总盐含量的比例增加了29%,非根际土壤增加26%。pH值与土壤NO_(3)^(-)含量呈显著负相关,与Na+含量呈显著正相关。32 g N·m^(-2)·a^(-1)处理下根际土壤的可溶性总盐含量比对照显著减少31.5%,氮沉降可以降低土壤pH值和根际土壤可溶性总盐含量,减轻盐碱胁迫。

We investigated the effects and mechanisms of nitrogen additions(0,1,2,4,8,16,24,32 g N·m^(-2)·a^(-1))on contents of anion and cation in rhizosphere soil,bulk soil,and mixed rhizosphere and bulk soil in the heavily salinized grassland in the agro-pastoral ecotone of North China.The results showed that pH of rhizosphere,mixed and bulk soils decreased significantly with the increases of nitrogen addition levels.Moreover,pH of three soil types under the 32 g N·m^(-2)·a^(-1)treatment decreased by 1.2,0.9,and 0.6,respectively,while pH of rhizosphere soil decreased by 0.44 compared with the bulk soil.Na+content of rhizosphere,mixed and bulk soils significantly decreased,while the NO_(3)^(-)content significantly increased.The proportion of Na+content in total soluble salt content in rhizosphere soil decreased by 14%and that in bulk soil decreased by 12%after the 32 g N·m^(-2)·a^(-1)addition.NO_(3)^(-)content increased by 29%in rhizosphere soil and by 26%in bulk soil.There was significant negative correlation between pH and NO_(3)^(-)content,and significant positive correlation between pH and Na+content.The total soluble salt content of rhizosphere soil under the 32 g N·m^(-2)·a^(-1)treatment was significantly reduced by 31.5%.Collectedly,nitrogen deposition could reduce soil pH and total soluble salt content of rhizosphere soil and alleviate saline-alkali stress.