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16 October 2025, Volume 58 Issue 20

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Intelligent Monitoring and Ecological Utilization of Saline-Alkaline Land

MEI XuRong, LI YuYi, WU WenBin, WU XuePing

Scientia Agricultura Sinica. 2025, 58(20):  4039-4046.  doi:10.3864/j.issn.0578-1752.2025.20.001

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REVIEW

Research on Ecological Protection Strategy for Comprehensive Utilization of Saline-Alkali Soil in China

LÜ GuoHua, WANG QingSuo, SONG JiaShen, LI YuYi, MEI XuRong

Scientia Agricultura Sinica. 2025, 58(20):  4047-4053.  doi:10.3864/j.issn.0578-1752.2025.20.002

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This study provided a systematic review of the ecological issues arising from the development of saline-alkali land in China. These included secondary salinization, the formation of groundwater depression cones, wetland shrinkage and functional degradation, and reduction in natural vegetation, as well as high remediation costs and pollution risks. In addition, it clarified the technological development pathways for the comprehensive utilization of saline-alkali land. These pathways encompassed four major directions: targeted strategies under a systematic management approach, cost-effective remediation under new ecological requirements, dual-force development through land-crop synergy, and specialized agriculture aligned with the broader concept of food. Furthermore, the study proposed an integrated strategy to strengthen the comprehensive management of saline-alkali lands, including emphasizing zonal rehabilitation of saline-alkali farmland, establishing a collaborative innovation system, and advancing fundamental theories and key technologies for sustainable utilization. It also recommended developing a tiered land-use model to support pilot programs for reserve resources and cultivated land, promoting specialized agriculture, enhancing productive capacity, advancing water-adapted planting, fostering innovation in water-saving agricultural technology, and strengthening ecological monitoring and impact assessment. This study provided the theoretical foundation and strategic support for ecological protection in the comprehensive utilization of saline-alkali land in China.

INTELLIGENT MONITORING OF SALINE-ALKALI LAND

Construction of Salinity Prediction Model Based on Optimal Selection of Soil Hyperspectral Characteristic Bands

LI MingLi, WEN CaiYun, MA DongHao, LI CunJun, WANG YuWen, KANG Lu, LU Miao

Scientia Agricultura Sinica. 2025, 58(20):  4054-4069.  doi:10.3864/j.issn.0578-1752.2025.20.003

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【Objective】Soil salinization is a key environmental problem threatening the sustainable development of agriculture in arid areas, leading to the deterioration of soil structure, crop yield reduction and ecosystem degradation. The purpose of this study is to use spectral transformation, band selection and a variety of machine learning methods to build a soil salinity prediction model, which can quickly and accurately estimate soil salinity, and provide technical support for the scientific management of salinized farmland.【Method】Taking farmland soil in Dalate Banner as the research object, soil samples were collected systematically and their electrical conductivity (EC) and spectral reflectance data were measured. Firstly, Savitzky-Golay (S-G) filter was used to smooth the original spectrum (R). On this basis, 12 kinds of spectral transformation processing including reciprocal, logarithmic, first-order differential and second-order differential were carried out to mine the hidden spectral features. Then, the correlation analysis (CA) and least angle regression (LAR) methods were used to reduce the feature dimension, and the competitive adaptive reweighted sampling (CARS) algorithm was combined to further screen the sensitive feature bands. Finally, partial least squares regression (PLSR), support vector machine (SVM), back propagation neural network (BPNN) and random forest (RF) models were constructed based on the optimal features. The performance of the model was comprehensively evaluated by determination coefficient (R²) and root mean square error (RMSE), and the modeling effects of feature sets in different algorithms were compared.【Result】After spectral transformation, the correlation coefficients of the original spectrum were improved in varying degrees, indicating that spectral transformation could significantly enhance the correlation between soil salinity and spectral characteristics; When CARS was used for feature band optimization, LAR had better feature dimension reduction effect than CA; The reciprocal logarithmic first-order differential (ATFD) combined with PLSR model performed best, and its validation set accuracy was R²=0.81, RMSE=2.04 dS·m^-1; The comparison of different modeling methods showed that the performance of PLSR prediction model was better than the other three models (BPNN/RF/SVM), indicating that PLSR model was more suitable for the prediction of soil salinity in this region.【Conclusion】The hyperspectral prediction model of soil salinity based on ATFD-LAR-CARS-PLSR has high accuracy and optimal prediction ability, which proves that hyperspectral technology combined with multi-dimensional feature optimization can effectively realize the prediction of soil salinity in arid areas.

Spatial Prediction of Deep Soil Salinization Based on Layered Modeling Using UAV Imagery

LEI MingKuo, ZHA Yan, WANG Li, CHENG Gang, WEN CaiYun, YIN ZuoTang, LU Miao

Scientia Agricultura Sinica. 2025, 58(20):  4070-4084.  doi:10.3864/j.issn.0578-1752.2025.20.004

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【Background】Soil salinization severely constrains crop growth and ecological balance, and its accurate monitoring is essential for saline-alkali land reclamation, yield forecasting, and precision farmland management. Driven by natural and anthropogenic factors, salinization is governed by the redistribution of water and salt within the soil profile, exhibiting pronounced vertical migration and strong spatial heterogeneity. Although unmanned aerial vehicle (UAV) remote sensing is now widely used for field-scale salinity mapping, it essentially captures surface information and fails to characterize salt gradients in deeper layers. 【Objective】To develop a UAV-image-based, layer-specific modeling framework that integrates machine learning with Kriging interpolation for high-resolution 3-D mapping of subsurface soil salinity.【Method】Firstly, the UAV was equipped with multispectral sensors to obtain high-resolution images of the test field, and the soil salinity data at different depths were measured synchronously, supplemented by real-time dynamic differential positioning technology to ensure spatial accuracy. Then, a spectral feature set including the red-edge band was constructed, and the feature optimization was carried out based on the random forest algorithm. On this basis, machine learning and Kriging interpolation method were combined to establish a stratified soil salinity prediction model and generate a high-resolution salinity distribution map. Finally, the advantages of the proposed method in the spatial representation of deep salinization were verified by comparing it with the cubic fitting depth function prediction method.【Result】The prediction accuracy R² of each depth of deep soil salinization spatial prediction by the mixed model hierarchical modeling was 0.68 (0-10 cm), 0.51 (10-20 cm), 0.58 (20-40 cm), 0.56 (40-60 cm) and 0.52 (60-80 cm), respectively, and the prediction effect of 0-10 cm surface layer was the best. The red-edged salinity index was an important predictor at all depths, which verified the applicability and effectiveness of the constructed red-edged index. By comparing the prediction results of the mixed model with the cubic fitting depth function, the spatial prediction accuracy of deep soil salinization in the layered model of the mixed model was higher, and it could more truly reflect the salinization degree at different depths in the experimental area.【Conclusion】UAV remote sensing technology is the best in shallow (0-10 cm) soil salinity prediction, and the prediction accuracy of soil properties decreases with the increase of depth, and the depth accuracy still needs to be improved. From the prediction results, the average soil salinity gradually increases with the increase of depth, indicating that there is an accumulation phenomenon of salt in the soil profile. Compared with the cubic fitting depth function method, the hybrid model based on random forest stratification modeling and Kriging residual correction shows higher spatial prediction accuracy in each soil layer, which is more reasonable and practical, and provides a scientific basis for dynamic monitoring of regional soil salinization and accurate layered soil salinity mapping.

BREEDING OF SALT-ALKALI TOLERANT VARIETIES

Identification of Salt Tolerance in Maize Natural Populations at the Seedling Stage and Analysis of Salt Tolerance-Associated Genes

WU ShuYu, HENG YanFang, YU TaiFei, WANG ShiJia, YU SiJia, LI Yuan, HU Zheng, ZHANG Hui, SUN XianJun, LI Liang, JIANG QiYan

Scientia Agricultura Sinica. 2025, 58(20):  4085-4099.  doi:10.3864/j.issn.0578-1752.2025.20.005

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【Objective】Soil salinization significantly impairs the growth and development of maize, resulting in reduced yields. Investigating the salt tolerance of various maize inbred lines and identifying favorable allelic variants associated with salt tolerance can provide valuable SNP markers and candidate gene resources for salt-tolerant maize varieties.【Method】This study utilized a natural population comprising 238 inbred maize lines as experimental materials. Twenty-day-old maize seedlings at the three-leaf stage were subjected to treatment with a 300 mmol·L^-1 NaCl solution, and changes in biomass, moisture contents as well as salt damage phenotypes were evaluated after 40 days of salt stress. A genome-wide association study (GWAS) was subsequently performed to identify favorable allelic variants associated with salt tolerance in maize.【Result】Through salt tolerance assessment of a maize natural population at the seedling stage, the materials were categorized into five distinct salt tolerance grades based on the salt damage rate: 22 highly tolerant materials (Grade 1), 93 tolerant materials (Grade 2), 62 moderately tolerant materials (Grade 3), 41 salt-sensitive materials (Grade 4), and 20 highly sensitive materials (Grade 5). The number of materials with different salt tolerance levels shows a normal distribution characteristic, with high-tolerance and highly sensitive materials comprising 17.6% of the total, while intermediate-grade materials accounted for 82.4%. Statistical analysis revealed that the salt damage rate was significantly and negatively correlated with the fresh weight, dry weight, and moisture content of plants under salt stress. The investigated traits exhibited considerable variability, indicating substantial differences among the genotypes. Genome-wide association analysis identified a total of 40 SNP loci associated with maize salt tolerance. Further investigation revealed one significantly associated SNP locus on chromosome 1 and another on chromosome 10. Analysis of the candidate genes within the 100 Kb confidence interval upstream and downstream of these two loci identified a total of 18 functional genes, including 9 genes with functional annotations and 9 genes with unknown functions.【Conclusion】22 first-class salt-tolerant maize inbred line materials were selected from a natural population consisting of 238 lines. 40 SNP loci associated with salt tolerance in maize seedlings were identified, among which two key SNPs showed significant association with the trait. Two salt tolerance-related candidate genes, ZmSTYK46 and Zm00001eb004810, were identified. ZmSTYK46 encodes a serine/threonine protein kinase, while the function of Zm00001eb004810 remains unknown.

Evaluation of Salt Tolerance in Newly Developed Zhongdan Series Maize Hybrid Varieties and Their Parental Inbred Lines

QU HaiYue, HAN JieNan, LI Ran, ZHANG Ze, LIU QianQian, HAO ZhuanFang, WENG JianFeng, ZHANG DeGui, ZHOU ZhiQiang, XU ZhenNan, RONG ZiGuo, WANG JuYing, YONG HongJun, LI MingShun

Scientia Agricultura Sinica. 2025, 58(20):  4100-4116.  doi:10.3864/j.issn.0578-1752.2025.20.006

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【Objective】The aim of the present study was to explore the correlation between seedling-stage salt tolerance in newly developed maize hybrids and salt tolerance in their parental inbred lines, evaluate the full growth-stage salt tolerance of hybrids with high seedling-stage salt tolerance, and provide resources and data support for development of maize hybrids suitable for saline-alkaline soils.【Method】Sixteen hybrid varieties and 30 parental inbred lines were used as materials for evaluating seedling-stage salt tolerance in 2024. The experiments were conducted in greenhouses at the Institute of Crop Science, Chinese Academy of Agricultural Sciences. Two treatments were applied: CK (control) and SA (salt stress treatment). Seedling-stage salt tolerance and correlation analyses were performed by measuring seedling height and biomass. Salt-tolerant hybrids were selected, and leaf yellowing percentage and sodium ion (Na⁺) content were analyzed in the latest developed leaves to further validate their salt tolerance. Additionally, salt tolerance during the germination stage was tested in hybrid varieties Zhongdan 1130, Zhongdan 1112, and Zhongdan 1118, and yield measurements were carried out in saline-alkaline soils of Dongying City, Shandong Province.【Result】Under 350 mmol·L^-1 NaCl stress, seedling height, fresh weight, and dry weight of the 16 hybrid varieties decreased by 53.73%-74.65% when compared with those in the control. Seven hybrids, including Zhengdan 958, Zhongdan 1130, Zhongdan 1112, and Zhongdan 1118, exhibited significantly higher morphological indices and salt tolerance coefficients than the average, demonstrating high salt tolerance. Under 250 mmol·L^-1 NaCl stress, salt tolerance was validated for some hybrids. Zhengdan 958 and Zhongdan 1130 exhibited significantly lower leaf yellowing percentages and Na⁺ contents in their aboveground parts than the salt-sensitive hybrids Zhongdan 153 and Zhongdan 123. Correlation analysis between the salt tolerance of the hybrids and those of their parental lines revealed that the salt tolerance coefficient of the aboveground fresh weight and seedling condition under salt stress of hybrids was significantly correlated with maternal line seedling condition (P<0.05). Kompetitive allele specific PCR analysis indicated no correlation between salt tolerance of hybrids and number of favorable allelic variations at the four salt tolerance loci in the parental inbred lines. In situ trials in moderately saline-alkaline soils throughout the entire growth stage showed that Zhongdan 1130 had a yield of 6 577.50-8 034.71 kg per hectare, which was 14.35%-20.99% higher than that of Zhengdan 958. Zhongdan 1112 yielded 6 415.11-7 720.73 per hectare, with either no yield reduction or an increase of 7.22%-34.22% when compared to that of Zhengdan 958. Zhongdan 1118 yielded 6 075.45-6 958.35 kg per hectare, with a yield increase of 5.62%-10.33% when compared to that of Zhengdan 958. 【Conclusion】Salt tolerance of maize hybrids is correlated with that of parental lines; however, the correlation is significant only with the seedling condition of the maternal line. The number of favorable allelic variations in the salt-tolerance genes SOS1, HKT2, HAK4, and HKT1;2 in the parental lines was not significantly correlated with the salt tolerance of the hybrids. The newly developed hybrid Zhongdan 1130, which has high seedling-stage salt tolerance, exhibited a stable yield increase of > 14.35% in saline-alkaline soils in Shandong compared to that of Zhengdan 958, making it a suitable, high-yielding, salt-tolerant variety for adoption in the Huang-Huai-Hai region.

Genetic Variation Analysis of New Germplasm with Combined High Yield and Salt Tolerance Developed from Derivative Materials of Pokkali

LIU ChunLei, WANG Juan

Scientia Agricultura Sinica. 2025, 58(20):  4117-4130.  doi:10.3864/j.issn.0578-1752.2025.20.007

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【Objective】This study aimed to elucidate the genetic basis of high yield and salt tolerance in rice through comparative genomic analysis of the salt-tolerant paternal parent Pokkali-D (Pokkali-Dwarf), the high-yielding maternal parent Huazhan, and their derived line Zhongyandao 16. The findings provide a theoretical foundation and genetic resources for the molecular breeding of salt-tolerant rice. 【Method】A new germplasm named Zhongyandao 16, which combines salt tolerance and high yield, was developed by crossing the salt-tolerant parent Pokkali-D with the high-yielding parent Huazhan. The salt tolerance of Zhongyandao 16 was evaluated based on seedling survival rate under salt stress (120 mmol·L^-¹ NaCl) and yield performance in a saline field (0.4% salinity). To further investigate the genetic basis of its superior traits, whole-genome resequencing of Pokkali-D, Huazhan and Zhongyandao 16 was conducted. Genetic variants inherited from both parents, as well as unique variants present in Zhongyandao 16, were screened through variant detection. High-impact variants (causing frameshifts or premature termination of translation) and moderate-impact variants (resulting in amino acid changes) were annotated for the affected genes. 【Result】Under 120 mmol·L^-1 NaCl stress, the seedling survival rate of Zhongyandao 16 was similar to that of Pokkali-D and significantly higher than that of Huazhan. Under normal field conditions, the yield of Zhongyandao 16 was comparable to Huazhan and significantly higher than Pokkali-D. Under 0.4% salinity field conditions, Zhongyandao 16 exhibited significantly higher yield than both parents, demonstrating a combination of salt tolerance and high yield. Comparative genomic analysis against the Nipponbare reference genome showed that Zhongyandao 16 shared 86 716 identical variants with Huazhan, among which high- and moderate-impact variants were annotated to 1 629 genes. It also shared 21 623 identical variants with Pokkali-D, with high- and moderate-impact variants annotated to 443 genes. Additionally, Zhongyandao 16 carried 372 unique variants, with high- and moderate-impact variants annotated to 11 genes. Functional screening of these 2 083 genes identified 16 involved in salt stress regulation (12 derived from Huazhan, 4 from Pokkali-D), 48 associated with yield-related traits (36 from Huazhan, 12 from Pokkali-D), and 3 modulated both yield and salt tolerance (2 from Huazhan, 1 from Pokkali-D). Notably, salt-tolerance alleles from Pokkali-D including OsPRPL18, OsSTLK, STH1, OsLPR2, and OsLPR5, as well as those from Huazhan, such as OsSAP4, OsY3IP1, OsABI5 and OsHKT1;5, were pyramided in Zhongyandao 16. 【Conclusion】By pyramiding yield-related genes from Huazhan and salt-tolerance alleles from Pokkali-D, Zhongyandao 16 combines high yield and salt tolerance. This demonstrates that introducing key salt-tolerant alleles from Pokkali-D into the high-yielding Huazhan background can effectively enhance salt tolerance without compromising yield.

SOIL MICROORGANISMS

Isolation and Identification of Rhizosphere Growth-Promoting Bacteria of Myroides odoratimimus PJ-3 and Their Salt/ Alkali-Tolerance and Growth-Promoting Effects on Maize

WU DongMing, XU Jing, YUAN JiaMei, WANG KeXuan, LI YuYi, HE Ping, ZHANG JianFeng, SONG DaLi, GAO Miao, ZHOU Wei

Scientia Agricultura Sinica. 2025, 58(20):  4131-4143.  doi:10.3864/j.issn.0578-1752.2025.20.008

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【Objective】Soil salinization is a significant limiting factor for global agricultural production and food security. Based on the mutualistic symbiotic relationships between rhizosphere beneficial bacteria (PGPR) and plants, this study aimed to screen out PGPR strains that possessed multiple functions, such as salt tolerance, alkali tolerance, and promoting growth, with the salt-stressed soil from maize rhizosphere. The study would provide raw materials and theoretical basis for the development of microbial agents for salt-alkali soil improvement and support the comprehensive management of salt-alkali land. 【Method】The PGPR strains were isolated by using the dilution plate coating method. The isolates were identified through morphological and microscopic observation, Biolog Gen III microplate analysis, and 16S rRNA gene sequencing. A microcosmic experiment was employed to assess the salt-alkali tolerance and plant growth promotion potential (PGP) of the PGPR strains. 【Result】23 PGPR isolates were screened and obtained, and the PJ-3 isolate exhibited the optimal salt-alkali tolerance and PGP potential. It was identified as Myroides odoratimimus with the attributes of Gram-negative. Specifically, the strain PJ-3 possessed a robust fructose-glycolytic pathway and lactic acid-pyruvate and phosphosugar transformation systems, enabling tolerance to extreme saline-alkaline conditions of up to 5% NaCl with a pH of 11. Pot experiments further demonstrated that under moderate saline-alkaline stress, the strain PJ-3 significantly increased maize germination rate of maize by 70% and promoted plant height, leaf length, leaf width, aboveground fresh weight, and belowground fresh weight by over 50%. Further analysis revealed that its superior tolerance and PGP mechanisms included the secretion of proteases, siderophores, and the plant hormone IAA (indole-3-acetic acid), activation of reactive oxygen species (ROS) scavenging by antioxidant enzymes SOD (superoxide dismutase) and CAT (catalase) in maize. Moreover, it could stimulate the conservative growth strategy in roots, with the enchantment in root surface area, root tip number, branching frequency and root vigor. As a result, these positive effects improved the improved chlorophyll a-dominated photosynthesis. 【Conclusion】Collectively, it was the first to report that Myroides odoratimimus PJ-3 possesses multiple novel functions, including remarkable salt tolerance, alkali tolerance, and the promotion of both aboveground and belowground development in maize. It demonstrated broad application potential for the integrated management of saline-alkaline lands and agricultural development.

Characterization and Utilization of Rhizosphere Microbiota from Wild Plants in Lalu Wetland in Xizang for Alleviating Saline-Alkali Stress in Maize

YANG Fu, WEI ShanJun, ZHANG XiaoXia, ZHANG LinMin, LIU HongXiu, LI YiJun, TONG YaPing

Scientia Agricultura Sinica. 2025, 58(20):  4144-4157.  doi:10.3864/j.issn.0578-1752.2025.20.009

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【Objective】Soil salinization poses a significant constraint on global agricultural development. However, microorganisms have shown the potential to mitigate salt stress in plants, and long-term intensive cultivation often leads to the unbalance of the beneficial microbial communities in agricultural soils. Isolating plant growth-promoting bacteria from the rhizosphere of wild plants in less disturbed habitats and introducing them into saline-alkali farmland offers a promising strategy to enhance crop tolerance to salt-alkali stress. 【Method】Isolation and culture of rhizospheric bacteria were performed using samples from five wetland plant species collected in the Lalu Wetland National Nature Reserve, Tibet. The isolates were preliminarily identified based on 16S rRNA gene sequencing. Functional characterization was further carried out using specific identification media. Finally, pot experiments were conducted to assess the effects of the selected promising microbial strains on the growth of maize seedlings. 【Result】A total of 260 strains were isolated from the rhizosphere soil of Erigeron canadensis, Galinsoga parviflora, Datura stramonium, Taraxacum mongolicum and Astragalus membranaceus, including 14 species and 21 potential novel species, and the dominant genus was Acinetobacter. 34 strains exhibiting inorganic phosphate-solubilizing capabilities and 47 strains demonstrating siderophore- producing functions were isolated through screening. Among them, strains 3-210 and 3-218 were identified as potential novel species of the genus Flavobacterium through genome analysis, and one key gene for plant hormone signal transduction GS2 was predicted. FeGenie predicted 50 and 71 iron related genes, respectively. No virulence factor genes related to the pathogenic process were detected. At the same time, the results of the pot experiment showed that inoculation of these two strains could improve the agronomic traits, such as plant height and stem diameter of maize seedlings. 3-210 treatment significantly increased the catalase activity and free proline content in leaves, and 3-218 group had significantly higher activities of the catalase and peroxide. 【Conclusion】The rhizospheric soils of plants in the Lalu Wetland National Nature Reserve, Tibet, harbored abundant functional bacterial resources, including multiple strains capable of siderophore production and phosphate solubilization. Notably, two potential novel species of the genus Flavobacterium demonstrated the ability to enhance saline-alkali stress tolerance in maize seedlings.

ECOLOGICAL UTILIZATION OF SALINE-ALKALI LAND

Intelligent Drip Irrigation Water-Fertilizer Coupling Regime Realizes Synergistic Improvement of Soil Water Conservation, Salt Control and Sunflower Yield and Quality

HAN ZheQun, SU Ying, GAO QiQi, LIU MeiYing, JIA AngYuan, ZHANG HaiRui, NAN ShanShan, XU QinZheng, WANG Qiang, WANG LiJun, WU XuePing

Scientia Agricultura Sinica. 2025, 58(20):  4158-4177.  doi:10.3864/j.issn.0578-1752.2025.20.010

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【Objective】In response to the issues of low soil fertility and water-salt imbalance constraining sunflower production in the saline-alkali soils of the Yellow River Irrigation Area (YRIA) in Inner Mongolia, this study investigated the regulatory effects of an intelligent drip irrigation-based water-fertilizer coupling regime on the saline-alkaline soil properties, as well as on sunflower growth and yield.【Method】Based on a two-year field study, this research employed a two-factor split-plot design conducted in Dalate Banner, Inner Mongolia, during 2023-2024. Sunflower was used as the test crop, with two irrigation methods, including surface irrigation and drip irrigation-assigned to the main plots, and four fertilization regimes applied in the sub-plots: chemical fertilizer alone (F), chemical fertilizer plus straw incorporation (FS), chemical fertilizer combined with cow manure (FM), and chemical fertilizer supplemented with high-carbon basal fertilizer (FH). The study evaluated the effects of different water-fertilizer management strategies on soil physicochemical properties, sunflower yield and quality, as well as nutrient physiological efficiency.【Result】Based on the two-year experimental period, the intelligent drip irrigation coupled with integrated water-fertilization practice significantly reduced soil electrical conductivity (EC) in the 0-40 cm layer by 41.2%, increased soil moisture content by 15.0%, elevated nitrate nitrogen (NO₃^--N) content by 37.8%, and enhanced soil organic carbon (SOC) content by 10.8%, compared with traditional flood irrigation with conventional fertilization. Under traditional flood irrigation, the application of organic amendments significantly decreased EC by 7.3%-27.0% and reduced pH by 0.08-0.51 units relative to the chemical-fertilizer-only (F) treatment, while increasing SOC by 3.8%-13.0%, NO₃^--N by 9.2%-58.2%, available phosphorus (AP) by 32.2%-62.7%, and available potassium (AK) by 12.4%-22.7% in the 0-40 cm soil layer. Under intelligent drip irrigation, organic amendments led to a reduction in EC by 3.7%-28.5% and increased in SOC by 4.3%-9.5%, NO₃^--N by 17.2%-61.4%, AP by 20.3%-48.8%, and AK by 3.6%-26.6%, compared with F treatment. In terms of crop performance, integrated intelligent drip irrigation with fertigation significantly enhanced sunflower plant height and stem diameter by 16.7% and 85.4%, respectively, over traditional flood irrigation. Nitrogen physiological efficiency (NPE) and phosphorus physiological efficiency (PPE) increased by 26.6% and 34.1%, respectively; biomass yield and grain yield rose by 12.8% and 89.5%, respectively; and water use efficiency (WUE) improved by 67.7%. Under traditional flood irrigation, organic amendments significantly raised plant height by 16.7%-17.5%, PPE by 27.1%, biomass yield by 37.0%-43.9%, grain yield by 6.0%-25.2%, WUE by 6.0%-25.2%, kernel percentage by 13.0%-17.9%, and grain fat content by 9.7% compared with F treatment. Under intelligent drip irrigation, organic amendments significantly improved plant height by 7.6%, NPE by 15.2%-17.2%, PPE by 17.2%, biomass yield by 23.7%, grain yield by 4.6%-20.4%, WUE by 4.6%-20.4%, kernel percentage by 6.2%-10.2%, and grain fat content by 3.3% relative to F treatment. Mantel analysis indicated that biomass yield and grain yield were significantly positively correlated with soil water content, SOC, plant height, stem diameter, NPE, and PPE (P<0.01), and significantly negatively correlated with pH and EC. In summary, the combined application of intelligent drip irrigation with water-fertilizer integration, particularly in conjunction with cow manure or high-carbon basal fertilizer, demonstrated the most favorable outcomes, representing the most suitable water and fertilizer management strategy for saline-alkali soils in the Yellow River irrigation area. 【Conclusion】 The integrated water-fertilizer regime under smart drip irrigation, combined with organic amendments, enhanced saline-alkali soil quality and sunflower productivity by effectively reducing soil salinity, improving nutrient availability, and increasing crop physiological efficiency.

The Effects of Biochar Combined with Fulvic Acid on the Physical and Chemical Properties, Enzyme Activities and Multifunctionality of Soil in Coastal Saline-Alkali Land

ZHANG HaiRui, JIA AngYuan, GAO QiQi, HAN ZheQun, NAN ShanShan, DUAN BiHua, WU XuePing

Scientia Agricultura Sinica. 2025, 58(20):  4178-4188.  doi:10.3864/j.issn.0578-1752.2025.20.011

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【Objective】This study aimed to explore the effects of biochar combined with fulvic acid on the improvement of coastal saline-alkali soil and its influence on soil multifunctionality (SMF), providing the theoretical support for the scientific application of biochar and fulvic acid.【Method】Based on a three-year field experimental study, four treatments were set up in the coastal saline-alkali land, including (control (CK), single application of 30 t·hm^-2 biochar (C₁), single application of 0.15 t·hm^-2 fulvic acid (H₁), and combined application of biochar and fulvic acid (C₁H₁). The soil physical and chemical properties and soil enzyme activities in the 0-10 cm, 10-20 cm soil layers and rhizosphere soil were determined, and the soil multifunctionality was calculated based on the average value method.【Result】The results showed that the combined application of biochar and fulvic acid could significantly improve the physical, chemical and biological properties of soil. Compared with CK, the soil bulk density under C₁H₁ treatment at 0-10 cm and 10-20 cm soil layers decreased by 9.2% and 11.2%, respectively; the saturated soil moisture content increased by 11.3% and 9.8%, respectively; the total soil porosity increased by 12.6% and 12.8%, respectively; the soil pH value decreased by 4.4% and 3.9%, respectively; the soil EC value decreased by 19.9% and 22.8%, respectively; the soil SOC increased by 44.6% and 44.7%, respectively; available phosphorus (AP) increased by 48.3% and 44.8%, respectively; the availability of potassium (AK) increased by 45.3% and 43.3%, respectively. The enzyme activity analysis revealed that C₁H₁ had the most significant promoting effect on the carbon-nitrogen cycle-related enzymes (β-glucosidase, cellobiose hydrolase, leucine aminopeptidase), with an increase ranging from 23.4% to 47%. Under the combined treatment of biochar and fulvic acid, the SMF index had the greatest increase, rising by 77.5%. 【Conclusion】The combined application of biochar and fulvic acid significantly enhanced soil multifunctionality by improving the pore structure of coastal saline-alkali land and increasing nutrient availability and enzyme activity.

Effects of Fertilization Management on Soil Carbon Fractions and Crop Yield of Post-Wheat Green Manure Rotation in Saline-Alkali Soils

YU Ru, LI YuYi, CAO JuFeng, MA Jun, CHANG FangDi, SONG JiaShen, ZHANG HongYuan, LI XiaoBin, LI HaoRuo, ZHANG Hua, WANG Jing

Scientia Agricultura Sinica. 2025, 58(20):  4189-4202.  doi:10.3864/j.issn.0578-1752.2025.20.012

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【Objective】This study was conducted to explore the effects of different chemical fertilizer optimization managements on the dynamics of soil organic carbon (SOC) fractions, soil carbon process, and subsequent spring wheat yield in a post-wheat green manure (hairy vetch, Vicia villosa Roth) rotation of saline-alkali soil in the Hetao Irrigation District. The aim was to identify effective fertilizer reduction pathways for synergistically enhancing soil carbon sequestration and productivity. 【Method】Based on a long-term filed experiment established in 2015 in Linhe District, Bayannaoer City, four treatments were set up by randomized block design, including CK (nitrogen, phosphorus and potassium fertilizer), K0G (nitrogen and phosphorus fertilizer), P0G (nitrogen and potassium fertilizer), and N0G (phosphorus and potassium fertilizer). SOC fractions and enzyme activities in 0-20 and 20-40 cm soil layers, and spring wheat yield were measured in 2023, and the soil carbon process index for soil carbon transformation intensity was also calculated. 【Result】(1) Compared with K0G and P0G treatments in 0-20 cm soil layer, N0G treatment (nitrogen fertilizer reduction) significantly reduced soil pH by 0.17 and 0.11 units, while significantly increasing available phosphorus (AP) content by 27.6% and 96.3%, respectively, and available potassium (AK) content by 26.5% and 46.3%, respectively. Compared with P0G, N0G treatment significantly increased AP and AK contents by 192.7% and 18.2% in 20-40 cm soil layer, respectively. (2) Compared with K0G and P0G treatments, N0G treatment significantly enhanced carbon-related enzyme activities in 0-40 cm soil layer: β-glucosidase (27.1% and 53.6%, respectively), xylanase (82.6% and 65.9%, respectively), and cellobiosidase (46.2% and 60.1%, respectively). (3) Compared with K0G and P0G, N0G treatments significantly increased labile organic carbon (LOC) by 25.7% and 26.3%, respectively, and particulate organic carbon (POC) contents by 50.0% and 48.8% in 0-40 cm, respectively. Compared with K0G, N0G significantly increased mineral-associated organic carbon (MAOC) content by 19.2% in 0-20 cm. SOC fractions showed significant positive correlations with soil nutrients and enzyme activities, but significant negative correlations with soil pH. (4) Spring wheat yield under CK, K0G, P0G and N0G treatments were 8.17, 7.76, 7.95 and 7.95 t·hm^-2, respectively. There was no significant difference between P0G, N0G and CK, except that K0G significantly reduced the yield by 5.1% compared with CK. Soil enzyme activities were the significant predictors of spring wheat yield. (5) N0G treatment exhibited higher carbon process index in both 0-40 cm layers, significantly exceeding K0G and P0G treatments. Spring wheat yield showed a significant positive correlation with the carbon process index in the 0-20 cm soil layer. 【Conclusion】N0G (multiple cropping of hairy vetch without nitrogen fertilizer after wheat) effectively reduced soil pH, activated carbon cycle-related enzyme activities, promoted organic carbon labile fractions accumulation, and enhanced carbon process index, ultimately increasing spring wheat yield of a wheat-green manure cropping system in the Hetao Irrigation District. Therefore, this approach was a viable fertilizer reduction strategy for harmonizing soil amelioration (pH reduction, C sequestration) with stable crop productivity in saline-alkali soil.

Winter Green Manure Enhances Soil Aggregation and Plant- and Microbial-Derived Carbon Sequestration in Coastal Saline-Alkali Soils

JIN XiaoYing, XIAO BingZheng, ZHANG TianJin, LIU ZhongKuan, FENG Wei, DU ZhangLiu

Scientia Agricultura Sinica. 2025, 58(20):  4203-4215.  doi:10.3864/j.issn.0578-1752.2025.20.013

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【Objective】This study aimed to investigate the characteristics of soil aggregation and molecular origins of soil organic matter (SOM) under winter green manure cropping systems, in order to establish a scientific foundation for organic matter sequestration and soil quality improvement in saline-alkali soils. 【Method】 The field experiment, initiated in 2019 in Huanghua County of Hebei Province, involved four treatments: winter fallow (CK), Orychophragmus violaceus (OV), Triticale (TG), and winter wheat (WW). The relative contributions of SOM from different origins and related factors were elucidated. Three biomarkers - lignin phenols, glomalin-related soil protein (GRSP), and microbial necromass carbon (MNC) - were conducted to quantitatively distinguish plant- and microbial-derived organic matter components. 【Result】 Green manure generally increased soil organic carbon (SOC) storage by 12.2%-21.8% (only TG showing significant difference) and total nitrogen storage by 22.5%-36.4% compared with CK. Additionally, green manure treatments enhanced the proportion of larger macroaggregates (>2-8 mm) by 1.9-6.2 times and smaller macroaggregates (0.25-2 mm) by 12.4%-74.6%, relative to CK. The OV, TG, and WW treatments increased the mean weight diameter of aggregates by 26.7%, 86.4%, and 113.8%, respectively, compared with CK. The OV, TG, and WW also exhibited a 16.3%, 57.3%, and 86.4% higher proportion of water-stable macroaggregates (>0.25 mm) than that under CK, respectively. Moreover, the OV enhanced concentrations of vanillyl by 37.7% and cinnamyl by 149.7%, compared with CK. The OV, TG, and WW treatments increased total lignin phenols by 74.6%, 32.9%, and 38.4%, respectively, relative to CK. Besides, TG had 36.5% higher easily extractable GRSP than that under CK. TG treatment increased total MNC by 60.6% compared with CK. Again, TG had higher contributions of bacterial necromass C (19%), fungal necromass C (38%), and microbial necromass C to SOC (57%), and the contributions of microbial-derived carbon to SOC was higher than that of plant-derived across green manure treatments. 【Conclusion】 It was concluded that adoption of winter green manure increased soil aggregation and promoted the accumulation of microbial-derived carbon, potentially boosting soil quality and C sequestration in the coastal saline soils.

Synergistic Effects of Post-Wheat Green Manure Rotation and Nitrogen Reduction in Saline-Alkali Soil on Wheat Yield, Environmental Footprint, and Economic Benefit

ZHANG MengXuan, CHANG FangDi, WEI HeYa, LI XiaoHong, WU LinMei, ZHANG HongYuan

Scientia Agricultura Sinica. 2025, 58(20):  4216-4230.  doi:10.3864/j.issn.0578-1752.2025.20.014

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【Objective】 This study aimed to investigate the impacts of post-wheat green manure rotation combined with nitrogen reduction on wheat yield, carbon and nitrogen footprints, and environmental-economic benefits in saline-alkali lands. It sought to drive the transition of agriculture in ecologically fragile regions from a "yield-oriented" model toward the coordinated achievement of three-dimensional goals-"resource conservation, environmental friendliness, and rational economic benefits", so as to provide a scientific basis and practical pathway for regional agricultural green transformation and efficient utilization of saline-alkali soils. 【Method】 A split-plot field experiment was conducted at the Yuanziqiao Experimental base of Bayannur Academy of Agricultural and Animal Sciences in the Hetao Irrigation District, Inner Mongolia. Main plots included green manure incorporation methods: green manure root stubble retention only (GMR) and full biomass incorporation (GMRS), while subplots comprised three nitrogen (N) application levels during the spring wheat season: conventional N (200 kg N·hm^-2, N100), 10% N reduction (180 kg N·hm^-2, N90), and 20% N reduction (160 kg N·hm^-2, N80), and a control with post-wheat fallow (CK) was established, totaling seven treatments. 【Result】 Compared with CK, green manure incorporation (GMR and GMRS) under reduced N regimes increased wheat yield by 6.2%-23.5%. The range of carbon and nitrogen footprints of wheat production under green manure rotation was 0.23-0.52 kg CO₂ eq·kg^-1 and 4.53-7.89 g N·kg^-1, respectively. Green manure treatments reduced carbon and nitrogen footprints by 13.0%-54.6% and 27.3%-47.6% relative to CK, respectively. The environmental damage cost under CK (caused by GHG emissions and reactive nitrogen losses) peaked at 5 053 CNY. Under N100, N90, and N80 regimes, GMRS increased damage costs by 5.0%, 7.7%, and 10.6% compared with GMR, respectively. Human health damage accounted for the largest proportion (47.1%-52.1%) of total costs. GMR significantly enhanced net ecosystem economic benefits by 6 742, 5 301, and 8 567 CNY (increases of 24.2%, 20.9%, and 35.9%) over GMRS, respectively, demonstrating superior economic-ecological synergies. 【Conclusion】 The post-wheat green manure system exhibited significant potential for environmentally friendly agriculture in saline-alkali ecosystems. Implementing “green manure incorporation + reduced N management,” particularly root stubble retention (GMR), ensures wheat yield, mitigated GHG and reactive nitrogen losses, increased economic returns, and provided a practical pathway toward sustainable intensification in ecologically vulnerable regions.

Effects of Calcium/Aluminum-Based Amendments on Saline-Alkali Soil Quality and Sunflower Yield in the Hetao Irrigation District

LI MingZhu, TIAN RongRong, LI Ran, WANG ShuJuan, WANG WeiNi, WANG Jing, LIU JunMei, LIU Jia, LI YuYi, XU LiZhen, LI Yan, ZHAO YongGan

Scientia Agricultura Sinica. 2025, 58(20):  4231-4245.  doi:10.3864/j.issn.0578-1752.2025.20.015

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【Objective】This study aimed to investigate the effects of calcium- and/or aluminum-based soil amendments on soil quality and sunflower yield in the Hetao Irrigation District of Inner Mongolia, China, so as to provide a theoretical support and technical guidance for the comprehensive governance of saline-alkali lands in the region.【Method】A two-year (2022-2023) field experiment was conducted in Ordos City, Inner Mongolia, with four treatments: control (CK), calcium-based amendment (Ca-based), aluminum-based amendment (Al-based), and calcium+aluminum-based amendment (Ca+Al-based). The experiment systematically assessed soil salinity indices and nutrient content in the 0-20 cm soil layer, as well as sunflower agronomic traits and grain yield at harvest. The soil quality index (SQI) was constructed using principal component analysis, and structural equation modeling was employed to reveal the effects of the amendments on SQI and sunflower yield. 【Result】Compared with CK, all three soil amendments improved the SQI and sunflower yield. Among the treatments, the Ca+Al-based amendment demonstrated the most promising results, specifically reducing soil pH by 0.09-0.24 units and sodium adsorption ratio by 14.3%-24.9%, and increasing soil available phosphorus by 72.7%-147.0% and nitrate nitrogen by 0.6%-89.6%. Consequently, it increased the SQI by 51.0%-58.0% and sunflower seed yield by 30.0%-51.4% compared with CK. The Ca-based treatment was less pronounced, with SQI increasing by 36.3%-51.0% and yield increasing only in 2022 (29.3%). Notably, soil electrical conductivity increased by 16.0%-70.4% under the Ca-based and Ca+Al-based treatments, primarily due to an increase in water-soluble Ca²⁺, Mg²⁺, and SO₄^2- concentrations, and did not lead to salt damage in plants. In addition, structural equation modeling revealed that the amendments exerted their effects by directly regulating soil salinity and nutrient indices, which indirectly increased SQI and yield. Furthermore, the contribution of soil salinity reduction to yield (79.2%) was greater than that of nutrient improvement (20.8%). 【Conclusion】The Ca+Al-based amendment demonstrated a synergistic effect in significantly improving soil quality and sunflower yield, making it a suitable option for further application in the Hetao Irrigation District of Inner Mongolia and similar ecological regions.

Mechanisms of Composite Interlayer in Regulating Water Infiltration, Evaporation, and Water-Salt Distribution in Saline-Alkali Soil

BAI XiaoLong, LIU Na, SONG JiaShen, WANG GuoLi, WANG WeiNi, LIU JunMei, LI YuYi

Scientia Agricultura Sinica. 2025, 58(20):  4246-4258.  doi:10.3864/j.issn.0578-1752.2025.20.016

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【Objective】This study aimed to investigate the regulatory mechanisms of different interlayer materials on water infiltration, evaporation, and water-salt distribution in saline-alkali soil, providing a theoretical basis for amelioration of saline-alkali soil. 【Method】A typical saline-alkali soil from Wuyuan, Inner Mongolia, was selected for laboratory soil column simulation experiments. Four treatments were established: CK (no interlayer), JG (straw interlayer), SC (mixed sand layer), and JS (combined mixed sand and straw interlayer), and the effects of composite and single interlayers on soil water infiltration processes, evaporation processes and salt variation patterns were investigated. 【Result】 When the wetting front moved to 40 cm, the interlayer treatment was 3.5%-10.6% longer than that under CK treatment, and 13.8%-55.2% longer than that under CK treatment when passing through the interlayer. The time of wetting front reaching the bottom of 100 cm under JG treatment was delayed by 780, 540, 120 min compared with CK, SC and JS treatment, respectively. After infiltration, the average soil water content under JG, SC and JS treatments in 0-40 cm soil layer was 22.9%, 18.7% and 21.9% higher than that under CK treatment, respectively. The soil salt content in the 0-40 cm soil layer was 18.6%-29.6% lower than that under CK treatment. The desalination rate under JS treatment in 40-70 cm soil layer was the highest, which was 49.4% lower than that under CK treatment. The salt content under each interlayer treatment in 70-100 cm soil layer was lower than that under CK treatment, and the decrease under JS treatment was the largest. During the continuous 45 d evaporation process, the interlayer significantly inhibited cumulative evaporation. The evaporation under CK treatment was 572 mm, and the evaporation under JG, SC and JS treatments decreased to 194, 235 and 205 mm, respectively, which was 66.1%, 58.9% and 64.2% lower than that under CK treatment, respectively. During the continuous evaporation process of 45 days, the water content of 0-100 cm profile of each treatment decreased with depth. In the 0-40 cm soil layer, the water content under CK treatment continued to decrease with the prolongation of evaporation time, and on the 15th, 30th and 45th days, the water content was 23.4%, 21.0% and 21.6%, respectively. The water content under JG, SC and JS treatments decreased by 14.6%-33.8%, 11.2%-17.0% and 14.9%-30.3% compared with CK treatment, respectively. The decrease of water content under JG and JS treatments was significantly greater than that under SC treatment. In the 45-60 cm soil layer, the water content under the interlayer treatment was higher than that under the CK treatment, and on the 15th day, the JG, SC and JS treatments increased by 4.8%, 3.7% and 5.4%, respectively. During the evaporation process, the salt content in the 0-100 cm profile of each treatment showed a 'low-high' distribution. In the 0-40 cm soil layer, the average soil salt content under JG, SC, and JS treatments was 35.0%-70.3%, 19.1%-51.4%, and 32.8%-62.7% lower than that under CK, respectively. In the 40-70 cm soil layer, the salt content of each treatment increased first and then decreased, and the JG, SC and JS treatments increased by 10.6%-14.4% compared with CK treatment. In the 70-100 cm soil layer, the average soil salt content under JG, SC and JS treatments was 8.4%-28.3% lower than that under CK treatment. 【Conclusion】 In summary, laying interlayers in saline-alkali soil could effectively regulate the distribution of water and salt. The effects of mixed sand layer and straw combined interlayer on inhibiting phreatic evaporation and salt return were better than that of single interlayer.

Effects of Ridge Tillage and Sowing in Furrow on Soil Water and Salt Dynamics and Maize Growth in Coastal Saline-Alkali Land

CHEN Jian, WU LiuGe, ZHANG Xin, DENG AiXing, SONG ZhenWei, ZHANG WeiJian, ZHENG ChengYan

Scientia Agricultura Sinica. 2025, 58(20):  4259-4271.  doi:10.3864/j.issn.0578-1752.2025.20.017

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【Objective】Studying the effects of different planting patterns on soil water-salt dynamics and maize yield could provide a theoretical basis for further enhancing the productivity of coastal saline-alkali lands. 【Method】 The experiment was conducted from 2022 to 2023 in the coastal saline-alkali soil of Dongying City, Shandong Province, using a split-plot design with two factors. The main plots consisted of two maize varieties: Zhongshi 8626 (V1) and Zhongdan 8922 (V2), while the subplots included three planting patterns: flat tillage (P1), ridge tillage and sowing on the ridge (P2), and ridge tillage and sowing in the furrow (P3). The study investigated the mechanisms by which ridge tillage and sowing in the furrow affects soil water-salt dynamics and maize yield. 【Result】 Compared with P1, P3 treatment increased soil water content in the 0-40 cm layer by 4.6% and reduced soil salt content by 10.3%, whereas P2 decreased water content by 4.8% and increased soil salt content by 11.8% during the maize seedling stage. The seedling emergence rate under P3 was 2.9% higher than that under P1. Ridge tillage and sowing in the furrow significantly improved topsoil water retention and reduced salinity, thereby enhancing maize emergence. At the silking stage, P3 increased root dry weight, root length, root surface area, and root volume by 18.5%, 21.1%, 23.1%, and 26.8%, respectively, compared with P1. At maturity stage, P3 increased dry matter accumulation, ear number, and kernels per spike by 10.2%, 3.1%, and 4.0%, respectively, compared with P1. The emergence rate of maize in V1 was 5.2% higher than that in V2. Compared with V1, V2 increased root dry weight, root length, root surface area, and root volume at the silking stage by 26.9%, 13.8%, 7.1%, and 26.0%, respectively. At maturity stage, V2 increased dry matter accumulation and 100-grain weight by 7.0% and 3.8%, respectively, compared with P1. However, V1 had 5.2% more ear numbers and 12.4% more kernels per spike than V2. In comparison with P1 and P2, P3 increased yield of V1 by 9.1% and 27.1%, respectively, while P3 increased yield of V2 by 10.7% and 19.0%, respectively. 【Conclusion】 Under the experimental conditions, the maize variety Zhongshi 8626 was selected and planted with ridge tillage and sowing in the furrow. This approach optimized soil water-salt dynamics, which contributed to higher seedling emergence rates, increased kernels per spike, enhanced harvest index, and improved grain yield.

Impacts of Secondary Salinization on Soil Quality and Cropland Productivity in the Yellow River Irrigation District

GAO QiQi, HAN ZheQun, ZHANG HaiRui, NAN ShanShan, HUANG YanYan, ZHU HengXia, WU XuePing

Scientia Agricultura Sinica. 2025, 58(20):  4272-4284.  doi:10.3864/j.issn.0578-1752.2025.20.018

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【Objective】This study aimed to explore the impact mechanism of soil secondary salinization on soil quality and cropland productivity, thereby providing a theoretical basis for improving saline-alkali soil and enhancing productivity in the Yellow River Irrigation District.【Method】In this study, typical saline-alkali cropland in Dalate Banner, Inner Mongolia was selected as the research area. Soil samples from the 0-20 cm soil layer were collected in May, July, and October 2023 using the systematic grid sampling method. A total of 17 soil indicators (encompassing physical, chemical, and microbial properties) were determined to analyze the spatiotemporal variation characteristics of soil salinization. The soil quality index (SQI) was evaluated by combining principal component analysis (PCA) with the weighting method. Additionally, linear regression, random forest model, and partial least squares path model (PLS-PM) were used to reveal the impact mechanism of soil salinization on the cropland productivity index (CPI).【Result】Soil secondary salinization indicators showed obvious spatial and temporal variability. Among them, soil electrical conductivity (EC) increased with the decrease of terrain, with the coefficient of spatial variation ranging from 29.2% to 61.2%. Moreover, the EC values in July and October increased by 82.6% and 161.6% respectively compared with those in May. The minimum data set for SQI constructed by PCA included mean weight diameter (MWD) of aggregates, available potassium (AK), and available phosphorus (AP). The average SQI in the study area was 0.50, and SQI<0.60 accounted for 77.1%, while the average CPI was 0.62, and CPI>0.80 accounted for 47.9%. Linear regression analysis showed that soil salinity indicators (especially EC) were negatively correlated with SQI and CPI, while SQI was significantly positively correlated with CPI (P<0.05). Random forest model results showed that EC in May had the greatest effect on SQI, and EC in July and October had the greatest effect on CPI. PLS-PM analysis revealed that soil secondary salinization indicators had a direct negative effect on CPI (standard path coefficient=-0.610, P<0.001) and an indirect effect through their negative impact on SQI (standard path coefficient=-0.694, P<0.001), with a total effect of -0.789.【Conclusion】Soil secondary salinization impaired cropland productivity through the dual pathways of direct salt toxicity and indirect reduction of soil quality. Therefore, a synergistic strategy of “salt control and quality enhancement” should be adopted to improve the productivity of salinized cropland in the Yellow River Irrigation District.

Effects of Groundwater Depth and Nitrogen Application on the Distribution of Soil Water and Salt and the Nutrient Absorption and Utilization of Winter Wheat

SHE YingJun, ZHOU ZiZhe, WU Ming, GUO Wei, SHI ChangJian, HU Chao, LI Ping

Scientia Agricultura Sinica. 2025, 58(20):  4285-4304.  doi:10.3864/j.issn.0578-1752.2025.20.019

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【Objective】This study aimed to explore the combined effects of groundwater depth (GWD) and nitrogen application on soil water and salt distribution, stratified residues of nitrogen and phosphorus, and nutrient absorption and utilization of winter wheat, and to determine the nitrogen (N) application threshold for shallow groundwater depth based on the salt balance of cultivated soil and stable crop yield. 【Method】A soil column simulation experiment was conducted with four GWD gradients (60, 90, 120, and 150 cm, labeled as G1, G2, G3, and G4) and four N application rates (0, 150, 240, and 300 kg·hm^-2, labeled as NF0, NF150, NF240, and NF300), resulting in 16 treatments. The experiment was carried out during the 2020-2021 and 2021-2022 winter wheat growing seasons to monitor and analyze the distribution of soil water and salt, the nitrogen and phosphorus content in different soil layers, and the nitrogen uptake and utilization of winter wheat under different GWD and N application combinations. 【Result】 Two years of data showed that increased application of N fertilizer exacerbated soil drought in the main root zone (0-60 cm soil layer, MRZ), especially, when the GWD was greater than G3, the soil moisture in the MRZ of the NF300 treatment was significantly reduced. Under N application of NF0-NF150, the electrical conductivity of the 0-20 cm and 20-60 cm soil layers showed a decreasing trend with increasing GWD, whereas under treatment of NF240-NF300, the electrical conductivity of the 20-60 cm soil layer in 2021-2022 and two-year salt accumulation significantly enlarged with increasing GWD. The N application of NF240-NF300 significantly augmented the salt content in the 0-20 cm soil layer at the depth of G3-G4, especially in the NF300 treatment where the soil conductivity of 0-20 cm soil layer exceeded the threshold (360.19-362.89 μs·cm^-1) and showed an obvious trend of alkalization. At the NF0-NF240 treatment, the average soil total nitrogen content under the MRZ of G3 and G4 treatments was the highest, while the total nitrogen and total phosphorus content were significantly reduced with increasing GWD under NF300 treatment. Among them, the average soil total nitrogen content under G1-G3 treatment was significantly higher than that under G4 treatment by 11.90% (P<0.05). Growing N fertilizer under G1-G2 depth was beneficial for increasing soil total nitrogen content, while soil total nitrogen content under NF150-NF240 treatment was the highest at the G4 depth. The soil total phosphorus content was the highest under the NF0-NF150 treatment with the G1-G4 depth. Increasing the GWD could promote the absorption of nitrogen by grains and the aboveground parts of plants under the NF0-NF240 treatment. However, with the continuous increase in N application rate and the superimposition of N application for groundwater control between years, the increase in the GWD was not conducive to the absorption of nitrogen by grains and the aboveground parts. Increased application of N fertilizer significantly promoted the N accumulation in grains and aboveground parts at the GWD of G1-G2. However, for the GWD of G3-G4, the N accumulation in grains and aboveground parts was the highest under the N application condition of NF150-NF240. Moreover, after continuous N application and groundwater control in 2021-2022, increased N fertilizer significantly reduced the nitrogen harvest index of winter wheat. 【Conclusion】 In conclusion, under the GWD of 120-150 cm, N application rate of 150-240 kg·hm^-2 was conducive to maintaining soil water-salt balance in the MRZ, enhancing N accumulation in aboveground parts and grains, and achieving both reduced N fertilizer input and improved efficiency while ensuring scientific management of the main root zone salinity.