宁夏银北地区是黄河中上游半干旱盐碱区的一个代表区域。银北地区是宁夏盐渍化土壤的集中地，银北地区的土壤盐渍化严重制约了其农业的发展。提升盐碱地改良技术水平，有助于提高土壤地力，降低盐碱化程度，促进粮食生产稳定发展，建设现代生态农业。近年来学术上对盐碱地改良技术的研究主要有单一措施和综合措施两种模式，而不同区域的盐碱地成因存在差异，单一措施很难确保在降低土壤pH和碱化度的同时实现对耕地肥力的提升，达到改良盐碱地的目的，因此设计综合改良模式，在改良盐碱地的同时实现对耕地肥力的提升才是更加符合农业生产实际的举措。

本文选取宁夏贺兰县为研究区，首先设计出四种符合当地现状的综合改良模式，分别是：磷石膏+有机肥+深耕深松（G1   ）、磷石膏+有机肥+秸秆还田（G2    ）、深耕深松+秸秆还田+磷石膏（G3）、深耕深松+秸秆还田+有机肥（G4   ），并对四种改良模式以对照试验的原则一一进行空间配套，其次通过物联网水盐动态监测、取土化验、抽样调查等多种手段对每种综合模式作用下的盐碱地土壤指标数据进行采集，使用特尔斐法构建出基于层次分析法的盐碱地改良效果评价模型，进一步对四种不同改良模式的改良效果进行模型运算，最后按照综合评价指数找出了最适合该区域的综合改良模式，为当地盐碱地标准化治理技术的推广提供了支撑。

本文主要研究成果如下：

（1）分析四种改良模式对于土壤盐基离子情况的改变，可以发现四种措施对八大盐基离子含量的改变情况不一，施用磷石膏的措施G1、G2、G3对SO₄^2-和Ca²⁺含量有促进作用，对Na⁺含量等有抑制作用，原因磷石膏施用会增加土壤中钙离子含量，与钠离子发生反应，生成Na₂SO₄随水运动排除土壤，从而降低土壤Na⁺含量。由于研究区盐碱地形成的主要原因是Na⁺盐，因此Na⁺含量的降低能一定程度上体现出改良效果的优劣。而四种模式在0-20cm土层土壤盐基离子的增减幅度要明显高于20-50cm，又说明土壤盐基离子空间变异性很大，并且在表层土壤中这种变异性更加明显。

（2）分析四种改良模式对于土壤pH和含盐量的影响，可发现四种改良模式在0-20cm、20-50cm土层均能不同程度降低土壤的pH值和含盐量，在改良效果方面四种改良模式排序为G2>G1>G3>G4，其中G2模式在0-20cm和20-50cm分别对改良效果评价得分情况贡献37.24%和20.52%的增长率，优于其他三种改良模式，且四种模式在0-20cm的改良效率均高于20-50cm，这说明改良措施在浅土层效果要优于深土层。

（3）分析四种改良模式对于土壤养分情况的改变，可以发现四种改良模式都有不同程度提升土壤养分的效果，而且提升土壤养分主要由施用有机肥和采用秸秆还田来决定，因此在四种综合改良措施中，同时包含有机肥和秸秆还田的改良措施对土壤养分的提升情况要明显高于只含有两者中一种的组合模式，G2和G4对土壤养分的改良情况要高于G1和G3也是因为这个原因。此外根据改良措施组合情况及综合指数提升效率，由G2和G4还可以分析出施用磷石膏相对深耕深松在养分提高方面效果更好，由G1和G3可以分析出有机肥在提升土壤养分方面效果要优于秸秆还田。

（4）采用层次分析法对四种改良模式进行综合评价，根据评价结果可知，采用磷石膏+有机肥+秸秆还田(G2)的综合模式对贺兰县盐碱地改良效果最好。G2模式不但提升土壤肥力强，对pH值和全盐含量的降低也明显高于其他三种模式。通过产量验证法、对比验证法和专家验证法三种方式对综合改良模式评价结果进行验证，发现评价结果与贺兰县盐碱地改良效果的实际情况相吻合。

（5）经过综合分析可知，G2对于盐碱土的改良效果最好。因此建议在宁夏回族自治区贺兰县使用磷石膏+有机肥+秸秆还田的改良模式进行盐碱土改良。该结论对宁夏回族自治区银北地区盐碱地改良具备一定参考价值。

In the middle and upper reaches of the Yellow River, Yinbei region of Ningxia is a representative region of a semi-arid saline-alkali region. Yinbei area is the concentration of salinized soil in Ningxia. The soil salinization in Yinbei area seriously restricts the development of its agriculture. Enhance the technical level of saline-alkali land improvement is helpful to improve soil fertility, reduce saline-alkali degree, promote the stable development of grain production and build modern ecological agriculture. In recent years, there are two modes of research on saline-alkali land amelioration: single measure and comprehensive measure. However, the causes of saline-alkali land in different regions are different, so it is difficult for a single measure to ensure the improvement of cultivated land fertility while reducing soil pH and alkalization degree, so as to achieve the purpose of saline-alkali land improvement. Therefore, it is more consistent with the actual agricultural production to design a comprehensive improvement mode to improve the saline-alkali land and improve the fertility of cultivated land at the same time.

This article selects the ningxia helan county as the study area. Firstly, four comprehensive improvement modes in line with the local situation were designed, which were: phosphogypsum + organic fertilizer + deep tillage and deep loosening (G1), phosphogypsum + organic fertilizer + straw returning to the field (G2), deep tillage and deep loosening + straw returning to the field + phosphogypsum (G3), deep tillage and deep loosening + straw returning to the field + organic fertilizer (G4). A nd the four improvement modes were matched in space one by one according to the principle of control experiment. Secondly through a variety of means such as iot water salt dynamic monitoring, soil testing, sampling survey, the soil index data of saline-alkali land under the action of each comprehensive mode were collected, using Delphi method to construct the evaluation model of saline-alkali land improvement effect based on analytic hierarchy process (ahp), of four different modified model for further improvement of model operation. Finally, according to the comprehensive evaluation index, we find out the most suitable comprehensive improvement mode for the region, which provides support for the promotion of the local saline-alkali land standardized treatment technology.

The main research results of this paper are as follows:

(1) By analyzing the changes of the four improvement modes on soil base ion, it can be found that the four measures have different changes on the contents of the eight base ions. Applying phosphogypsum measures G1, G2 and G3 can promote the contents of SO₄^2- and Ca²⁺, but inhibit the contents of Na⁺.The reason for this phenomenon is that CaSO₄, as the main component of phosphogypsum, will increase the content of Ca²⁺ in soil colloid after it is applied to the soil, and Ca²⁺ can react with the Na⁺ contained in soil colloid to form sulfate, and finally remove the soil with the movement of water, thus reducing the content of Na⁺ in the soil. Since the main reason for the formation of saline-alkali land in the study area is Na⁺ salt, the reduction of Na⁺ content can reflect the merits and demerits of the improvement effect to a certain extent. However, the increase and decrease of base ions in the 0-20cm soil layer of the four patterns were significantly higher than that in the 20-50cm soil layer^[1], it also indicates that the soil salt base ions have great spatial variability, and such variability was more obvious in the surface soil.

(2) By analyzing the influence of the four improvement modes on soil pH and salt content, it can be found that the four improvement modes can reduce soil pH and salt content to different degrees in 0-20cm and 20-50cm soil layer. In terms of improvement effect, the four improvement modes are ranked as G2>G1>G3>G4. Among them, G2 mode contributed 37.24% and 20.52% growth rates to the improvement effect evaluation score in 0-20cm and 20-50cm respectively, which was better than the other three improvement modes.

(3) By analyzing the changes of the four improvement modes on soil nutrients, it can be found that the four improvement modes all have different effects of improving soil nutrients, and the effects is mainly determined by the application of organic fertilizer and straw returning measures. Therefore, among the four kinds of comprehensive improvement measures, the comprehensive improvement measures that include both measures have significantly higher improvement of soil nutrients than other combination modes.

(4) Analytic Hierarchy Analysis (AHP) was used to make a comprehensive evaluation of the four improvement modes. According to the evaluation results, the comprehensive mode of phosphogypsum + organic fertilizer + straw returning (G2) had the best effect on the improvement of salt-alkali land in Helan County.G2 model not only improved soil fertility, but also significantly reduced pH value and total salt content than the other three models.The evaluation results of the comprehensive improvement model were verified by yield verification method, comparative verification method and expert verification method, and it was found that the evaluation results were consistent with the actual situation of the improvement effect of saline-alkali land in Helan County.

(5) Through comprehensive analysis, G2 has the best improvement effect on saline-alkali soil. Therefore, it is suggested to use the amelioration mode of phosphogypsum + organic fertilizer + straw returning to improve the saline-alkali soil in Helan County, Ningxia Hui Autonomous Region. This conclusion has certain reference value for the improvement of saline-alkali land in Yinbei area of Ningxia Hui Autonomous Region.