我国主要菜区耕层土壤盐分总量及离子组成

Total salt content and ion composition in tillage layer of soils in the main vegetable production regions of China

【目的】评价全国主要菜区温室、大棚和露地菜田土壤盐分及离子组成状况,为土壤次生盐渍化防治、蔬菜合理施肥和土壤可持续利用提供一定的理论依据。【方法】在我国北方3个区域(东北、华北、西北地区)和南方4个区域(华中、西南、华东、华南地区)主要蔬菜种植区不同栽培方式典型菜田耕层土壤展开调查,共采集501个土壤样品,分析了盐分总量及其离子组成。【结果】1)全国主要菜区设施(温室和大棚)菜田土壤盐分总量及其各离子含量(NO_3^-、SO_4^(2-)、Cl^-、Na^+、K^+、Ca^(2+)、Mg^(2+))均显著高于露地菜田土壤,盐分总量平均高69.3%,离子组成增加幅度在36.2%170.0%之间。2)设施菜田土壤次生盐渍化的土样数比例显著高于露地菜田土壤,但设施菜田土壤盐化程度总体上较轻,居于轻度盐化水平的比例占38.2%,处于中度盐化以上水平的比例仅占4.7%。3)设施菜田土壤盐分总量及主要盐分离子(NO_3^-、SO_4^(2-)和Ca^(2+))含量积累总体上随种植年限的延长呈先增后降并趋于平缓的变化趋势,在连续种植5 6年时达到高峰期,之后因采取的各种管理措施而有所降低,但仍显著高于露地菜田土壤。4)设施菜田土壤盐分离子组成以NO_3^-和SO_4^(2-)为主,其次是Ca^(2+),分别占盐分总量的27.9%、26.9%和15.3%。露地菜田土壤主要盐分离子组成总体上是SO_4^(2-)>NO_3^->Ca^(2+)、HCO_3^-,分别平均占盐分总量的29.0%、21.1%、16.1%和14.1%,但西北地区露地菜田土壤盐分离子组成以HCO_3^-为主,其次是SO_4^(2-)、NO_3^-和Ca^(2+)。【结论】设施菜田土壤次生盐渍化的土样数比例虽然显著高于露地菜田土壤,但土壤盐化程度总体上较轻,盐分离子主要是NO_3^-、SO_4^(2-)和Ca^(2+),NO_3^-、SO_4^(2-)含量大于Ca^(2+)含量;露地菜田主要盐分离子是SO_4^(2-)、NO_3^-、Ca^(2+)和HCO_3^-,含量为SO_4^(2-)>NO_3^->Ca^(2+)、HCO_3^-。

【Objectives】The investigation on the total salt content and the main ions will provide a scientific basis for prevention and remediation of secondary soil salinization caused by fertilization in vegetable production.【Methods】In this study,501 representative soil samples in plow layers were collected from the main vegetable production regions in the Northeastern,North,Northwestern,Southwestern,Central,East and South China. The total salt content and the ratio of main salt ions NO_3-,SO_4-（2-）,HCO_3-,Cl-,Na-＋,K-＋,Ca-（2＋） and Mg-（2＋） in the samples were analyzed.【Results】1） The contents of total salt and individual salt ions（ NO_3-,SO_4-（2-）,Cl-,Na-＋,K-＋,Ca-（2＋）and Mg-（2＋）） in the vegetable soils of greenhouse（with back wall and without back wall） were 69. 3%,36. 2% to 170% higher than those in open fields（ P 0. 05）,respectively. 2） The percentage of soil samples withtotal salt contents beyond the critical value of secondary salinization（ soil total salt content ≥ 2 g / kg） in the greenhouse vegetable fields was distinctly higher than in the open fields. The greenhouse vegetable fields were still in generally light degree of salinity,38. 2% of them belong to light salinity（ 2- 5 g / kg）,and 4. 7% belong to medium and above medium salinity（ ≥ 5 g / kg）. 3） The total salt contents and main ion composition（ NO_3-,SO_4-（2-）and Ca-（2＋）） in greenhouse vegetable soils tended to accumulate fast at first,and reached peaks in the 5th to 6th year of vegetable production,then slowed down and kept stable. 4） In greenhouse vegetable fields,NO_3-and SO_4-（2-）were the dominant ions,averagely accounting for 27. 9% and 26. 9% of the total salt content,respectively. The contribution of NO_3-and SO_4-（2-）to the total salt content varied in different greenhouse vegetable production regions.Ca2＋was the second main contributor to the total salt contents,averagely accounting for 15. 3%. In the open fields,the major salt ions were SO_4-（2-）,NO_3-,Ca-（2＋） and HCO_3-,their contribution to the total salt contents was generally in order of： SO_4-（2-） NO_3- Ca-（2＋） and HCO_3-,the SO_4-（2-）,NO_3-,Ca2＋and HCO_3-contents accounted for29. 0%,21. 1%,16. 1% and 14. 1% of the total salt content,respectively. In Northwestern China,HCO_3- was the major salt ion in open vegetable soils,followed by SO_4-（2-）,NO_3-and Ca-（2＋）. 【Conclusions 】 Although the percentage of soil samples with total salt contents beyond the critical value of secondary salinization was distinctly higher in greenhouse than in the open vegetable fields,the greenhouse vegetable fields were still in generally light degree of salinity. The major salt ions contribution to the total salt contents was generally in order of： NO_3-,SO_4-（2-）Ca-（2＋） for the greenhouse vegetable fields,and SO_4-（2-） NO_3- Ca2＋and HCO_3-for the open vegetable fields.