滨海土壤因长期受到海水浸渍、泥沙淤积而形成，除存在盐碱胁迫较大、矿质养分偏低等不利因素外，在土壤微生物方面还存在结构单一、区系紊乱等问题。在该类土壤中直接种植粮食或饲料作物很难形成较高的生物量和有效产量，因此有必要根据“生物质添加、有机酸辅助及微生物促进”原则设计外源复合型盐碱土改良剂，综合分析其对土壤盐碱降低及养分活化，进而促进作物生产的效应和机理。本试验采用盆栽土培的方式并结合实验室分析开展研究，试验用土取自江苏省盐城东台条子泥垦区，供试甜高粱（Sorghum bicolor L.）品种为“大力士”（Hunnigreen）。试验设计有机酸、生物材料及复合微生物3个处理因素，其中有机酸设2种类型：柠檬酸（C）、富里酸（F），生物材料设2种类型：松针（PN）、牛粪（DM），复合微生物制剂设3种类型：巨大芽孢杆菌+哈茨木霉菌（MT）、枯草芽孢杆菌+黑曲霉菌（SA）以及短小芽孢杆菌+淡紫拟青霉菌（PP），对照（CK）为不施用改良剂种植的甜高粱。在植物出苗后的20 d、40 d和60 d采集植物样品，在30 d、60 d和90 d采集土壤样品，测定甜高粱生长指标和生理生化指标，滨海盐碱土壤理化和盐碱指标以及细菌群落特征，探讨有机酸生物材料与复合微生物制剂对甜高粱生长性能和盐碱土壤降盐培肥的综合效果，确定滨海盐碱地的有机酸生物材料和复合微生物最佳复配组合。主要研究结果如下：

1.有机酸、生物材料接种复合微生物制剂，能够显著缓解甜高粱的盐碱胁迫效应，从而获得较高的生物产量。其中，较不施添加剂处理（CK）相比，有机酸、生物材料配施复合微生物制剂的甜高粱株高、茎粗、鲜重、根长与生物量显著提高（P＜0.05），最高增幅达424.18%，根系活力、抗氧化酶活性、叶绿素和脯氨酸的含量显著提高（P＜0.05），最高增幅达208.94%，丙二醛含量显著降低、超氧阴离子自由基产生速率显著变慢（P＜0.05），最高降幅达90.00%。以柠檬酸+松针+巨大芽孢杆菌+哈茨木霉菌（CPN+MT）处理对甜高粱生长20 d和40 d的各指标影响最显著，而到达60 d后，以富里酸+松针+短小芽孢杆菌+淡紫拟青霉菌（FPN+PP）处理对甜高粱生长性能提升效果最好。

2.不同有机酸、生物材料接种复合微生物制剂处理较CK均能显著降低土壤酸碱度、盐度以及电导率（P＜0.05），最大降幅达21.2%，改善了土壤理化性质并提高土壤肥力，显著提升土壤含水量并降低容重（P＜0.05），显著增加土壤有效磷和碱解氮含量（P＜0.05），最大增幅达394.38%，最大降幅达20.92%，土壤根际酶活性显著提高（P＜0.05），最高增幅达331.45%，其中以CPN+MT处理在20 d和40 d土壤盐分降低、土壤物理结构改善、肥力和酶活性提升效果最佳，但在60 d时，其作用效果低于FPN+PP处理。

3.有机酸、生物材料接种复合微生物的甜高粱根际土壤细菌群落隶属于51个门，147个纲，312个目，463个科，682个属。甜高粱根际土壤Alpha多样性中的Chao1指数、Shannon指数（Shannon-Wiener）和Faith_pd指数（Faith’s Phylogenetic Diversity）指数存在显著差异（P＜0.05），其中FPN+PP处理的Chao1指数和Shannon指数最高，CPN+MT的Faith_pd指数最高，Beta多样性存在显著差异（P＜0.05），且与CK差异最大的是CPN+SA处理。不同处理均对细菌群落组成结构产生影响，优势细菌门主要是变形菌门（Proteobacteria）和酸杆菌门（Acidobacteriota），其中，FPN+PP处理对Proteobacteria的丰度提升最大，FDM+SA对Acidobacteriota的丰度提升最大，而不同处理的绿弯菌门（Chloroflexi）丰度较CK均下降。此外，甜高粱根际土壤理化性质与其细菌群落的多样性及其在门水平上的丰度密切相关。

总之，CPN+MT处理可有效调控滨海盐碱地的理化性质，显著优化土壤盐分分布与速效养分，为甜高粱幼苗期提供良好的立地条件。FPN+PP处理具备持续改良土壤的功效，不仅能优化微生物群落结构，还可确保滩涂种植的甜高粱在生育中后期保持稳健生长态势，最终实现生物产量的显著提升。因此，在滨海盐碱地区，可依据耐盐牧草的生长特性，采用CPN+MT处理提升刈割型饲草的鲜重产出，运用FPN+PP处理有效促进青贮、籽粒型牧草的干物质积累，从而为高效生产的饲草种植体系构建及滩涂盐碱土地资源高效利用奠定实践基础与科学依据。

Coastal mudflats are formed by long-term seawater impregnation and sedimentation, and in addition to the unfavorable factors such as high saline and alkaline stress and low mineral nutrients, there are also the problems of single structure and disorganization of soil microorganisms. It is difficult to form high biomass and effective yield by directly planting food or feed crops in such soils, so it is necessary to design exogenous compound saline-alkaline soil conditioner according to the principle of “biomass addition, organic acid assistance and microbial promotion”, and comprehensively analyze its effect on soil salinity reduction and nutrient activation, and then promote crop production. This study used pot experiments and laboratory analyses to investigate these effects. The soil used in the experiment was taken from Yancheng, Jiangsu Province, Dongtai, Tiaozini Wetlands. The sweet sorghum (Sorghum bicolor L.) variety for the test was “Hunnigreen”. Three treatment factors were designed. Among them, there were 2 types of organic acids: citric acid (C) and fulvic acid (F), 2 types of bio-based materials: pine needle (PN) and dairy manure (DM), and 3 types of composite microbial agents: Priestia megaterium + Trichoderma harzianum (MT), Bacillus subtilis + Aspergillus niger (SA), and Bacillus pumilus + Paecilomyces lilacinus (PP). The control (CK) was sweet sorghum grown without amendments. Plant samples were collected on 20, 40 and 60 d after the emergence of plants, and soil samples were collected on 30, 60 and 90 d after the emergence of sweet sorghum. The growth and physiological and biochemical indexes of sweet sorghum, the physicochemical saline-alkali indices and bacterial community characteristics of coastal saline-alkali soil were determined. The effects of organic acid biomaterials inoculating composite microorganisms on the growth performance of sweet sorghum and salt reduction and fertilizer cultivation in saline-alkali soil were evaluated. The optimum combination of organic acid biomaterials and composite microorganisms in coastal saline-alkali land was determined. The main results were as follows:

1. The application of organic acid, biomaterials with inoculated composite microorganisms were able to attenuate the effects of salinity and alkali stress in sweet sorghum, which resulted in a reorganization of plant morphology, leading to higher biomass yields. Among them, compared with no additive treatment (CK), plant height, stem diameter, singe plant fresh weight, root length and single plant biomas of sweet sorghum treated with organic acid, biomaterials combined with composite microbial agents, were significantly increased (P＜0.05). The highest increase was 424.18%. Root activity, antioxidant enzyme activity, chlorophyll and proline contents were significantly increased (P＜0.05), with the highest increase of 208.94%. The content of malondialdehyde was significantly decreased, and the production rate of superoxide anion radical was significantly slowed down (P＜0.05), with the highest decrease of 90.00%. Among them, citric acid+pine needle+P. megaterium+T. harzianum (CPN+MT) treatment had demonstrated the most significant effect on the growth indexes of sweet sorghum by 20 and 40 d, whereas fulvic acid+pine needle+B. pumilus+P. lilacinus (FPN+PP) treatment had established the best growth performance by the 60 d observation period.

2. Compared with CK, organic acids, biomaterials, and composite microorganisms had significantly reduced soil pH, salinity, and conductivity (P＜0.05) and had achieved a peak reduction of 21.2%. It improved soil physicochemical properties and soil fertility, significantly increased soil moisture content and decreased soil bulk density (P＜0.05), and significantly increased soil available phosphorus and alkali-hydrolyzed nitrogen contents (P＜0.05). The maximum increase was 394.38%, the maximum decrease was 20.92%. Soil rhizosphere enzyme activity was significantly increased (P＜0.05), and the maximum increase was 331.45%. Among them, CPN+MT treatment had the best effect on soil salinity reduction, soil physical structure improvement, fertility and enzyme activity improvement at 20 and 40 d. But at 60 d, the impact of FPN+PP treatment was less pronounced than that of FPN+PP treatment.

3. The rhizosphere soil bacterial communities of sweet sorghum supplemented with organic acids, biomaterials and composite microorganisms belonged to 51 phyla, 147 classes, 312 orders, 463 families and 682 genera. There were significant differences in Chao1 index, Shannon index (Shannon-Wiener) and Faith_pd index (Faith’s Phylogenetic Diversity) in sweet sorghum rhizosphere soil Alpha diversity (P＜0.05). Among them, the Chao1 index and Shannon index of FPN+PP treatment were the highest. Faith_pd index of CPN+MT treatment was the highest. There was a significant difference in Beta diversity (P＜0.05). The bacterial community of CPN+SA treatment was the most different from CK. Different treatments influenced the composition and structure of bacterial populations. The dominant bacterial phyla were Proteobacteria and Acidobacteriota. Proteobacteria abundance increased the most with FPN+PP treatment, while Acidobacteriota abundance improved the most with FDM+SA. When compared to CK, the abundance of Chloroflexi declined in various treatments. Moreover, the diversity and phyla-level abundance of bacterial communities in the sweet sorghum rhizosphere soil were significantly associated with its physical and chemical characteristics.

In conclusion, CPN+MT treatment effectively regulated the physical and chemical properties of coastal saline-alkali land, significantly optimized the distribution of soil salt and available nutrients, and provided favorable site conditions for the seedling stage of sweet sorghum. FPN+PP treatment was effective in continuously improving the soil. It not only optimized the microbial community structure but also ensured that sweet sorghum grown on tidal flats maintained a stable growth trend in the middle and later stages of growth, ultimately achieving a significant increase in biological yield. Therefore, in coastal saline-alkali areas, based on the growth characteristics of salt-tolerant forage grasses, CPN+MT treatment was adopted to increase the fresh weight yield of moat-type forage grasses, and FPN+PP treatment was used to effectively promote the dry matter accumulation of silage and grain-type forage grasses. Thus, a practical foundation and scientific basis was laid for the construction of an efficient forage planting system and the efficient utilization of saline-alkali land resources in tidal flats.