桑干河流域典型粮果农田土壤水盐氮分布特征

Distribution Characteristics of Soil Water, Salt and Nitrogen in Typical Grain and Fruit Farmland in Sanggan River Basin

桑干河流域是建设首都水源涵养功能区和生态环境支撑区的主要流域,针对目前流域内面源污染和土壤退化等生态问题,探究不同农田系统土壤水盐氮分布特征对于区域科学管理土地资源和调控水盐肥具有重要意义。以桑干河流域3种典型的农田利用方式(杏园、雨养玉米和灌溉玉米)为研究对象,通过野外取样与试验分析对不同农田利用方式土壤剖面水、盐和硝态氮分布规律进行研究,进而明晰土壤盐氮潜在淋溶风险。结果表明:①不同农田类型中灌溉玉米土壤含水率和电导率均值最高,杏园含水率最低,而电导率接近于雨养玉米。②土壤盐分离子组成以Na^(+)和SO_(4)^(2-)为主,K^(+)、Mg^(2+)和Cl^(-)相对较少,灌溉玉米中Na^(+)、K^(+)和Mg^(2+)均显著高于杏园。③土壤水盐分布因农田利用方式的不同而存在明显差异且分布复杂,杏园土壤电导率与盐分离子垂直分布呈橄榄形,雨养玉米SO_(4)^(2-)和电导率表现为中上多、底部少,灌溉玉米Na^(+)呈S形波动。④灌溉玉米NO_(3)^(-)-N平均累积含量明显高于雨养玉米和杏园,剖面分布为上下多、中间少的特点,且深层土壤NO_(3)^(-)-N均值达14.6 mg/kg,具有潜在的硝态氮淋溶风险。⑤不同利用方式土壤Mg^(2+)和SO_(4)^(2-)分别与含水率和电导率呈极显著正相关,其是控制区域水盐变化的重要因子。综上,不同农田利用方式对土壤水盐氮分布特征影响差异明显,灌溉玉米土壤水盐氮含量明显最高,需采取合理的水肥管理措施,减缓环境污染风险。

The Sanggan River Basin is located in the construction area of the capital water conservation area and eco-environment supporting area.However in the past decades,Sanggan River Basin was suffering severe non-point source pollution and ecological degradation.Exploring the mechanisms of changes in soil water,salt and nitrogen distributions in different farmland systems is critical for mitigating regional ecological crisis.In this syudy,three typical farmland use patterns (apricot garden,rain-fed corn and irrigated corn) in Sanggan River Basin were taken as the research objects,the distribution laws of water,salt and nitrate in soil profiles of different farmland use patterns were studied through the field sampling and experimental analysis.The aim was to clarify the potential leaching risks of soil salt and nitrogen.The results showed that:①The average values of soil water content and electrical conductivity of irrigated corn farmland were the highest in different farmland use types,while the moisture content of apricot orchard was the lowest,and the electrical conductivity was close to that of rain-fed corn.②Na^(+)and SO_(4)^(2-)were the main components of soil salt ions,while K+,Mg^(2+)and Cl^(-)were relatively few.Na^(+),K+and Mg^(2+)in irrigated corn were significantly higher than those in apricot garden.③The distribution laws of soil water and salt were obviously different with complex distributions,and this was mainly due to different farmland management patterns.The vertical distributions of soil electrical conductivity and salt ions in apricot orchards were olive-shaped,that of SO_(4)^(2-)and electrical conductivity in rain-fed corn was higher in the middle and upper part,but less in the bottom,and Na^(+)in the soil of irrigated corn was S-shaped.④The average cumulative content of NO_(3)^(-)-N in irrigated corn was significantly higher than that in rain-fed corn and apricot garden,and the profile distribution was characterized by more from top to bottom and less in the middle.The average NO_(3)^(-)-N in deep soil reached 14.6 mg/kg,which had potential nitrate leaching risk.⑤Mg^(2+)and SO_(4)^(2-)in different land use types were positively correlated with water content and electrical conductivity,respectively,indicating that they were important factors to control regional water and salt changes.To sum up,different farmland uses patterns have obvious differences on soil water,salt and nitrogen distribution characteristics,and the content of water,salt and nitrogen is obviously the highest in irrigated corn soil,so it is necessary to take reasonable water and fertilizer management measures to mitigate environmental pollution risks.