Search Results (34)

This study addresses secondary soil salinization driven by shallow groundwater in the Yanqi Basin of southern Xinjiang, focusing on subsurface drainage system (SDS) optimization for salt regulation and oil sunflower productivity improvement in severe saline–alkali soils. Through controlled field experiments conducted (May–October 2024), we evaluated five SDS configurations: control (CK, no drainage) and four drain spacing/depth combinations (20/40 m × 1.2/1.5 m). Comprehensive monitoring revealed distinct spatiotemporal patterns, with surface salt accumulation (0–20 cm: 18.59–32.94 g·kg⁻¹) consistently exceeding subsurface levels (>20–200 cm: 6.79–17.69 g·kg⁻¹). The A3 configuration (20 m spacing, 1.5 m depth) demonstrated optimal root zone desalination (0–60 cm: 14.118 g·kg⁻¹), achieving 39.02% salinity reduction compared to CK (p < 0.01). Multivariate analysis revealed strong depth-dependent inverse correlations between groundwater level and soil salinity (R² = 0.529–0.919), with burial depth exhibiting 1.7-fold greater regulatory influence than spacing parameters (p < 0.01). Crop performance followed salinity gradients (A3 > A1 > A4 > A2 > CK), showing significant yield improvements across all SDS treatments versus CK (p < 0.05). Multi-criteria optimization integrating TOPSIS modeling and genetic algorithms identified A3 as the Pareto-optimal solution. The optimized configuration (20 m spacing, 1.5 m depth) effectively stabilized aquifer dynamics, reduced topsoil salinization (0–60 cm), and enhanced crop adaptability in silt loam soils. This research establishes an engineering framework for sustainable saline–alkali soil remediation in arid basin agroecosystems, providing critical insights for water–soil management in similar ecoregions. Full article

In arid regions, soil salinization and inefficient water use are major challenges to sustainable agricultural development. Optimizing subsurface drainage system layouts is critical for improving saline soil reclamation efficiency. This study conducted field experiments from 2023 to 2024 to evaluate the effects of varying subsurface drainage configurations—specifically, burial depths (1.0–1.5 m) and pipe spacings (20–40 m)—on drainage and salt removal efficiency in silty loam soils of southern Xinjiang, aiming to develop an optimized scheme balancing water conservation and desalination. Five treatments (A1–A5) were established to measure evaporation, drainage, and salt discharge during both spring and winter irrigation. These variables were analyzed using a water balance model and multifactorial ANOVA to quantify the interactive effects of drainage depth and spacing. The results indicated that treatment A5 (1.5 m depth, 20 m spacing) outperformed all the others in terms of both the drainage-to-irrigation ratio (R_d/i) and the drainage salt efficiency coefficient (DSEC), with a two-year average R_d/i of 32.35% across two spring and two winter irrigation events, and a mean DSEC of 3.28 kg·m⁻³. The 1.5 m burial depth significantly improved salt leaching efficiency by increasing the salt control volume and reducing capillary rise. The main effect of burial depth on both R_d/i and DSEC was highly significant (p < 0.01), whereas the effect of spacing was not statistically significant (p > 0.05). Although the limited experimental duration and the use of a single soil type may affect the generalizability of the findings, the recommended configuration (1.5 m burial depth, 20 m spacing) shows strong potential for broader application in silty loam regions of southern Xinjiang and provides technical support for subsurface drainage projects aimed at reclaiming saline soils in arid regions. Full article

As extreme rainfall events become more frequent, leading to increased waterlogging hazards, it is crucial to explore various drainage methods that can alleviate the adverse effects of waterlogging on crop growth, thus addressing challenges related to global food security. Field experiments were carried out to evaluate the impacts of different drainage technologies on waterlogging mitigation, rice growth, dry matter accumulation, and yield. The experimental setup included varying straw blind ditch spacings (2, 3, 4, and 5 m) and subsurface pipe drainage spacings (6, 9, and 12 m), with surface drainage serving as the control (CK). The findings revealed that, in comparison to pipe drainage treatments, blind ditch treatments enhanced subsurface drainage volume by 15.1%. Regarding groundwater levels and soil moisture, the soil moisture in the 0–90 cm soil layer and groundwater levels under the blind ditch treatments were 11.3% and 6.1% lower than those under the CK as well as 22.0% and 23.9% lower than the pipe drainage treatments, respectively. Subsurface drainage treatments led to significant improvements in rice yield, with blind ditch and pipe drainage treatments increasing the yield by 8.0% and 6.0% compared to the CK. Rice yields initially increased before decreasing as burial spacing reduced. The S3 treatment resulted in yield increases of 14.4%, 8.6%, and 10.7% over the S2, S4, and S5 treatments, respectively. The G9 treatment produced 3.6% and 10.4% higher yields compared to the G6 and G12 treatments. The highest rice yield, 7.501 Mg·ha⁻¹, was achieved with a blind ditch spacing of 3 m. Compared to the S4 and S5 treatments, the yield per hectare for the S3 treatment was higher by 0.592 Mg and 0.726 Mg, while the input cost was higher by CNY 3038 and 4560, respectively. Path analysis indicated that root biomass made the largest direct contribution (0.517) to the increase in rice yield. Subsurface drainage contributed to the regulation of soil moisture, reducing leaf biomass while increasing stem biomass, which enabled the blind ditch treatments to produce optimal rice yield. These results provide a scientific basis for agricultural drainage in waterlogged areas. Full article

The salt distribution characteristics in arid areas are directly related to the sustainable development of agriculture. We study the characteristics of spatial changes of soil water and salt in farmland under the full anniversary of different culvert pipe arrangements and optimize the salt drainage parameters of underground drains suitable for the local area so as to promote the management of saline and alkaline land in Xinjiang. A subsurface drainpipe salinity test was conducted in the Yanqi Basin (Bayingoleng Mongolian Autonomous Prefecture, Xinjiang Uygur Autonomous Region, China) to analyze changes in soil water and salt dynamics before and after irrigation-induced salt flushing, assessing the impact of drainpipe deployment parameters. It was found that at a 1.4 m depth of burial, the maximum desalination rates of soil in different soil layers from the subsurface drainpipes in 20, 30, and 40 m spacing plots were 78.28%, 50.91%, and 54.52%, respectively. At a 1.6 m depth of burial, the maximum desalination rates of soil in different soil layers from the subsurface drainpipes in 20, 30, and 40 m spacing plots were 70.94%, 61.27%, and 44.12%. Reasonable deployment of subsurface drainpipes can effectively reduce soil salinity, increase the desalination rate, and improve soil water salinity condition. This study reveals the influence of the laying parameters of subsurface drainpipes on soil water salinity distribution characteristics in arid zones, which provides theoretical support and practical guidance for the management of soil salinization in arid zones. Full article

Groundwater conditions are crucial for understanding the evolution of soil salinization. The installation of subsurface pipes significantly alters both the distribution of water and salt in the soil and the groundwater depth; these dynamics and their interrelationships warrant further investigation. To clarify the relationship between groundwater dynamics and changes in water and salt in soil under subsurface pipe salt drainage conditions in the Yinchuan region of Ningxia, groundwater observation wells and soil sample monitoring points were established in Pingluo County. A combined approach of in situ monitoring and laboratory testing was employed to analyze changes in groundwater depth and salinity and their effects on water and salt in soil. The findings revealed that changes in groundwater depth and salinity exhibited clear seasonal patterns. The groundwater depth was deepest at 1.97 m in October and shallowest at 1.62 m in July. The salinity was highest at 22.28 g/L in April and lowest at 18.24 g/L in August. In summer, the groundwater was shallower and had lower salinity, while in other seasons, it was deeper with higher salinity. Soil salinity was lowest in July at 4.58 g/kg and highest in April at over 5.5 g/kg. It decreased with increasing groundwater depth, demonstrating a linear relationship. Additionally, soil salinity and groundwater salinity exhibited synchronous fluctuations, exhibiting an exponential relationship. Based on these observations, a model was developed to describe the relationship among groundwater salinity, groundwater depth, and soil salinity under subsurface pipe salt drainage conditions in the Yinbei region of Ningxia. This model was validated against measured data, yielding a correlation coefficient R² of 0.7238. These findings provide a reference for analyzing the relationship between soil salinity and groundwater in similar regions. Full article

The study aims to explore saline drainage modeling in coastal saline soils, particularly focusing on subsurface pipe drainage in the Shanghai coastal area. Utilizing Hydrus-2D/3D-2.05 software, dynamic changes in soil–water–salt under various subsurface pipe laying conditions in forested areas were simulated to identify optimal schemes. Indoor and outdoor experiments demonstrated the Hydrus model’s ability to effectively simulate soil–water–salt transport processes under complex conditions. Subsequent simulations under different parameters of underground pipe laying, including burial depths (D = 0.5/0.7/0.9/1.1/1.3/1.5 m) and pipe diameters (Ø = 8/10/12 cm), further corroborated model validation. Among the analyzed schemes, those with burial depths around 0.7 m and pipe diameters under 12 cm exhibited the most substantial salinity improvement. Regression analysis highlighted a significant impact of burial depth D on cumulative salt discharge, with a coefficient of 12.812, outweighing that of pipe diameter Ø. Furthermore, subsurface pipe laying schemes demonstrated long-term benefits and cost advantages, obviating the need for additional irrigation infrastructure. These findings underscore the significance of subsurface pipe drainage in enhancing soil quality, reducing construction expenses, and optimizing land utilization, providing a valuable foundation for the Shanghai Green Corridor development and related initiatives. Full article

Subsurface pipes covered with geotextiles and filters are essential for preventing clogging and ensuring efficient drainage. To address low salt discharge efficiency due to subsurface drainage pipes (SDPs) clogging easily, sand gravel, straw, and combined sand gravel–straw were set above SDPs, respectively, within a setting of uniform geotextiles. The influences of different filter materials on the drainage efficiency and salt discharge effect of the SDPs, as well as the effects of different filter materials on the salt drainage efficiency and anti-siltation effect of the SDPs were studied by performing simulation experiments in a laboratory. The results confirmed the following: (1) The salt removal rates of the SDPs externally wrapped with materials exceeded 95%. The subsurface pipe treated with the sand gravel filter material had the highest desalting rate (93.69%) and soil profiles with total salt contents that were 17.7% and 20.5% lower than those treated with the straw and combined sand gravel–straw materials, respectively. (2) The soil salinity of the sand gravel filter material around the SDPs was between 1.57 and 3.6 g/kg, and the drainage rate (R) was 0.97, so its salt-leaching effect was the best. (3) The sand gravel filter material increased the characteristic particle size of the soil above the SDP by 8.4%. It could effectively intercept coarse particles, release fine particles, and facilitate the formation of a highly permeable soil skeleton consisting of coarse particles, such as sand particles surrounding the soil. (4) The use of the straw filter material produced dense filter cake layers on the upstream surfaces of the geotextiles. When the sand gravel and combined sand gravel–straw filter materials were used, soil particles remained in the geotextile fiber structure, and a large number of pores were still retained. Therefore, the sand gravel filter material was the most suitable for the treatment of Yinbei saline–alkali soil in Ningxia Hui Autonomous Region. Full article

Subsurface drainage pipes covered with filters and geotextiles are the key to preventing clogging and ensuring efficient drainage. To improve the salt discharge efficiency of these subsurface drainage pipes, different layers of geotextiles were set outside the pipes with the aid of uniform gravel filters. This paper reports our findings from laboratory simulation of subsurface drainage pipes and experiments. The study examined the influence of different layers of geotextiles on the drainage efficiency, salt discharge effects of subsurface drainage pipes, and the effect of superimposed geotextiles on the salt drainage efficiency as well as the anti-clogging effect of subsurface drainage pipes. The results are as follows: (1) The geotextile and filter material wrapped around the subsurface pipe facilitated the movement of water towards the subsurface pipe, which could promote the salt discharge of the subsurface pipe. However, in the single leaching experiment, the reduction in soil pH was not significant for different scenarios. (2) The salt removal rate of the geotextile-wrapped subsurface pipes was more than 95%. The salt removal rate of the double-layer geotextile scenario was the highest (96.7%), and the total salt content of soil profiles was 8.3% and 31.3% lower than those of the single-layer and triple-layer geotextile scenarios, respectively. The drainage efficiency of the double-layer geotextile scenario was the highest, and the salt distribution in the 0–60 cm profile was relatively uniform, ranging from 2.3 to 3.0 g∙kg⁻¹. (3) The clogging in the triple-layer geotextile scenario was caused by the geotextile, i.e., a dense filter cake layer formed on the surface of the geotextile. The clogging in the single-layer and double-layer geotextile scenarios was the clogging of the geotextile itself, i.e., soil particles retained in the fiber structure of geotextiles. (4) In the case of the single-layer and double-layer geotextile scenarios, the soil particles failed to completely clog the selected geotextiles, and there were still a large number of pores retained. The double-layer geotextiles integrate filtration, clogging prevention, and drainage promotion to provide the best salt drainage with the subsurface pipe. This study reveals the influence of the filter on soil water salt and salt discharge and provides a theoretical explanation and technical justification for the application of the subsurface pipes salt discharge technology in saline soil ameliorate. Full article

Subsurface drainage and organic fertilizer application are two important measures for improving saline–alkali soils, while the effects of different drainage spacings combined with organic fertilizer application amounts on alfalfa growth and coastal saline soil properties have seldom been evaluated. This study designed subsurface drainage pipes at four spacing distances, including 0 m (CK, without subsurface drainage), 6 m (S1), 12 m (S2), and 18 m (S3), and three organic fertilizer application amounts, including 3000 kg/ha (N1), 4500 kg/ha (N2), and 6000 kg/ha (N3), to observe the effects of different combinations of subsurface pipe spacings and organic fertilization amounts on alfalfa yield, quality, soil salinity, and nutrients. The results showed that the yield of alfalfa increased with higher fertilization amounts and smaller spacing between drainage pipes. The highest yield occurred in the S1N3 treatment, and the three batches reached 1268.5 kg/ha, 3168.0 kg/ha, and 2613.3 kg/ha, respectively, significantly (p < 0.05) higher than CK for all three batches. The increase in organic fertilizer amount resulted in an increase of 0.5–9.3% in the crude protein content, a decrease of 1.8–3.4% in the neutral detergent fiber content, and a decrease of 1.3–5.5% in the acid detergent fiber content for alfalfa plants. Under CK, the contents of quality indicators in alfalfa were the highest. For the drainage treatments, the quality indicator contents were overall at a higher level under S3. Subsurface drainage had a reduction effect on the salinity of all the 0–80 cm soils. For the surface soil, it was detected that smaller spacing was beneficial for reducing soil salt content, while higher fertilization amounts increased the salt content. S1 reduced the soil salt content by 36.3–46.1% compared to CK; however, N3 increased the salt content by 7.0–16.2% compared to the other two fertilization treatments. In addition, smaller spacing between the subsurface drainage pipes generally reduced the soil’s available nitrogen, and total nitrogen increased the C/N ratio but had no significant effect on the organic matter. It was concluded that the spacing between subsurface drainage pipes and the application amounts of organic fertilizer have remarkable impacts on alfalfa yield and quality, mainly by changing the soil salinity and nutrient status. Full article

Subsurface pipe drainage (SPD) is an important technique for the improvement of saline–alkali lands in China. Winter irrigation after crop harvest is a key measure used in the Yellow River irrigation area in northwest China to reduce soil salinity in the root zone of crops. To optimize winter irrigation under SPD, the calibrated HYDRUS-2D model was utilized in this study to investigate the effects of soil texture (clay loam, silt loam, loam, and sandy loam), initial soil salinity (1, 3, 5 g/kg), and the winter irrigation quotas (80, 100, 120, 150, 180 mm) on the rate of soil desalination. In this study, soil salinity levels during the stable production of common crops such as sunflower and corn in the Yinbei Irrigation District in Ningxia, China, were taken as the thresholds, efficient utilization of irrigation water was considered, and suitable crops and appropriate winter irrigation quotas for different soil textures and levels of soil salinity were proposed. Soil with a salt content of 1~3 g/kg is suitable for the planting of corn with 80 mm of irrigation water. Sandy loam soil with a salt content of 3~5 g/kg is suitable for sunflower–corn intercropping with 120 mm of irrigation water. Sandy loam soil with a salt content exceeding 5 g/kg is suitable for the planting of sunflower with 80 mm of irrigation water. Other types of soils need to be improved by reducing the spacing between subsurface pipes, using desulfurized gypsum, biochar, and other additives. People engaged in agriculture can utilize this research to determine the appropriate volumes of irrigation water, crop types, planting systems, and subsurface pipe parameters based on local conditions. Full article

Soil salinization affects more than 25% of land globally. Subsurface pipe drainage is known for its effectiveness in improving saline–alkali land. The red clay layer (RCL) hinders soil improvement in the Hetao Irrigation District of Inner Mongolia, China. The soil water and salt migration rules at different buried depths and RCL were studied based on the field subsurface pipe drainage test and simulation using the DRAINMOD-S model (Version 6.1). The following implications can be drawn from the results: (1) Although the RCL affected the accuracy of the model, the calibrated statistical results met the application requirements, and the DRAINMOD-S model can be used to analyze subsurface pipe drainage under different distribution conditions of the RCL. (2) The RCL can reduce the drainage efficiency of the subsurface pipe, specifically when the distribution is shallow. (3) The soil desalting rate increased with an increase in the buried depth of the subsurface pipe. The desalination effect of shallow soil was better than that of deep soil. The RCL reduced the drainage and salt removal efficiency of the subsurface pipe. Burying the subsurface pipe as far above the RCL as possible should be considered. Thus, it is feasible to apply the DRAINMOD-S model to relevant studies. Full article

Controlling drainage during the growth stage is one of the means to provide suitable water and fertilizer conditions for crops, alleviate environmental pollution, and increase crop yield. Therefore, in this study, we studied three drainage treatments: free drainage (FD) and growth-stage subsurface controlled drainage (CD) at depths of 40 cm (CWT1) and 70 cm (CWT2). We used the HYDRUS-2D model to simulate the dynamic changes of NO₃-N in the 0–100 cm soil layer as well as NO₃-N uptake by crops, leaching after irrigation and fertilization, and loss through subsurface pipes in 2020 (model calibration period) and 2021 (model validation period). The degree of agreement between the simulated and measured values was high, indicating a high simulation accuracy. CD increased the soil NO₃-N content and crop NO₃-N uptake, and decreased NO₃-N leaching and loss. We observed significant differences in the soil NO₃-N content after irrigation at the budding stage of oilseed sunflower between CD and FD, with the largest difference seen for the 0–40 cm soil layer. CD increased crop yield, and the average oilseed sunflower yield of the CWT1 and CWT2 treatments increased by 4.52% and 3.04% relative to the FD treatment (p < 0.05). CD also enhanced nitrogen use efficiency. In moderately salinized soil, CD at 40 cm (CWT1) reduced the nutrient difference in vertical and horizontal directions while retaining water and fertilizer. CWT1 stabilized the groundwater depth, reduced the hydraulic gradient of groundwater runoff, and decreased the drainage flow rate. The NO₃-N leaching and loss dropped, which promoted crop nitrogen uptake and utilization, improved nitrogen use efficiency, reduced nitrogen loss, and had a positive effect on protecting the soil and water environment. The results demonstrate that CD is a suitable drainage method for the experimental area. Full article

The subsurface pipe drainage project is essential in farmland drainage operations and is globally recognized as an effective saline–alkali land improvement measure owing to its efficient drainage capacity and low land occupation rate. This study aimed to establish enhanced methods for improving saline–alkali land by combining ditching with subsurface pipe drainage. The ditching was conducted at a depth of 60 cm based on the existing subsurface pipe arrangement. The calibrated DRAINMOD-S model was employed to simulate the test area with different ditching depths and subsurface pipe arrangement parameters. Furthermore, the law of soil water and salt transport in the subsurface pipe drainage system at different ditching depths was investigated. After ditching, the total unit drainage volume of leaching increased by an average of 14.65% over two years and the water storage of different soil layers in the different plots decreased by 1.37–1.48 mm on average. Ditching demonstrated a superior salt-leaching effect in areas with subsurface pipe layouts. The soil desalination rate of different soil layers increased by 6.40–13.40% on average, with a more significant impact on the surface soil desalination rate. The effect of the increased desalination rate was more apparent as the ditching depth increased. However, as the buried depth of the subsurface pipe increased, the relationship between the ditching depth and soil desalination rate became insignificant. Ditching improved the salt-leaching effect of subsurface pipe drainage projects, which can effectively reduce the cost of subsurface pipe burial, consequently promoting subsurface pipe use. Full article

The agricultural development of reclaimed coastal areas in Jiangsu Province is significantly hindered by high soil salinity and an inadequate irrigation and drainage infrastructure. Optimizing the layout of subsurface drainage systems has been identified as an effective means of reducing soil salinity, with the proper designation of engineering parameters being crucial. This study applied 12 treatments (T1–T12) consisting of four different spacings of subsurface drainage pipes (6 m, 11 m, 15 m, and no subsurface drainage pipes) and three observation wells at varying distances from the drainage outlet (5 m, 25 m, and 45 m). Results showed that all three subsurface pipe spacing treatments significantly reduced soil salinity compared to natural drainage, with a smaller subsurface pipe spacing treatment leading to better salt-reducing effects. The farther the distance from the measuring point to the drain, the higher the salinity. As the burial depth of the outlet decreased and spacing between the subsurface drainage pipes decreased, the salinization rate of the 0–60 cm soil layer was higher, while the salt accumulation in the 60–80 cm soil layer was more severe. Therefore, a subsurface drainage pipe spacing of 6 m and an outlet burial depth of 40 cm are recommended as more suitable choices to effectively control salt concentration in the soil. The research aimed to provide scientific reference data and technical support for the optimized design of subsurface drainage engineering parameters while promoting efficient desalination of saline-alkali areas worldwide. Full article

As an effective method to improve saline–alkali land, the drainage from subsurface pipes has been extensively studied in typical arid and semi-arid agricultural areas (Hetao Irrigation District). However, there are few studies on the improvement of subsurface pipe layout and the long-term soil salinization control in the process of leaching and soil amendment with subsurface pipes in this area. This study investigated the water and salt migration in the process of amending the heavy saline soil. Field experiments growing sunflowers and numerical model calculation were combined in this research. It was found in the field experiment that the salt concentration in the surface pipe drainage was positively correlated with the salt content in the soil and the depth of the pipe, while it was negatively correlated with the amount of irrigation water and the spacing of crops. Thus, the soil desalting rate (N) and salt control rate (SCR) were positively correlated with the depth of the pipe, and they were negatively correlated with the spacing. The leaching effect of irrigation would decrease when the soil salt content decreased. On the basis of field experiments, the DRAINMOD model and drainmod equation were used to calculate the water and salt migration in 38 different field plots during 2019 and 2020. When N was the same, the soil salinity in several plots with large burial depth could be controlled below the salt tolerance threshold of sunflowers during the growth period in the second year. The quantitative relationship between N and SCR, soil salt content before leaching, water amount of leaching, pipe spacing and buried depth was already established. These results can help develop strategies for desalination and salt control in the soil in the arid and semi-arid areas with the optimal layout of subsurface pipes. Full article