Evaluation of drainage systems performance using digital soil salinity mapping

Document Type : Research Paper

Authors

• Farhad Dehghani ¹
• Yosef Hasheminejhad ²
• Amir parnian ³
• Nadia Besharat ⁴

¹ Faculty member, National Salinity Research Center (NSRC), Agricultural Research, Education ‎and Extension ‎Organization (AREEO), Yazd, Iran

² Faculty member, Khorasan Razavi Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education ‎and Extension ‎Organization (AREEO), Mashhad, Iran

³ Faculty member, ‎National Salinity Research Center (NSRC), Agricultural Research, Education and Extension ‎Organization (AREEO), Yazd, Iran

⁴ ‎National Salinity Research Center (NSRC), Agricultural Research, Education ‎and Extension ‎Organization (AREEO), Yazd, Iran

Abstract

Keywords

• Drainage
• Electromagnetic Induction
• Evaluation
• Pistachio
• Salinity

Main Subjects

• ..

Introduction:

The effective management of soil salinity in the root zone is a critical factor for sustaining agricultural productivity in irrigated lands, particularly in arid and semi-arid regions. One robust method to assess the performance of agricultural drainage systems is to analyze their impact on soil salinity control. This study focused on evaluating the performance of the rehabilitated and modernized drainage systems in the Tanour-Lahour region, Yazd Province, using advanced spatial sampling and data analysis techniques.

Materials and Methods:

A Latin hypercube sampling (LHS) strategy was employed to enhance the efficiency and representativeness of the sampling process, allowing for the systematic collection of 147 soil samples, 28 water samples, and 225 electromagnetic conductivity (EM) readings across the study area. The LHS approach ensured comprehensive spatial coverage, reducing the potential bias associated with traditional random or grid sampling methods. Laboratory analysis was conducted on soil and water samples to measure salinity content and ionic composition, providing the basis for mapping soil salinity variations within the root zone. These maps were created through geostatistical interpolation methods, offering a visual and quantitative representation of salinity distribution in the study area.

Results and Discussion:

The results of this study demonstrated the significance of combining field measurements with indirect estimation techniques for assessing soil salinity. Regression analysis using both direct and inverse modeling approaches revealed that among the various electromagnetic device measurements, only the horizontal position measurements of apparent electrical conductivity (ECa) showed a significant correlation with the average root zone salinity. This finding underscores the importance of proper sensor orientation and the need for calibration in salinity assessment studies.

Traditional methods of salinity assessment, based solely on soil sampling and laboratory analysis, were found insufficient to provide an accurate and holistic view of salinity dynamics and the drainage system's performance. In contrast, the integration of indirect measurements, such as ECa data, with laboratory analyses offered a more comprehensive understanding of salinity levels and their spatial variability. This integrated approach provided better insights into the relationship between soil salinity, plant health, and the efficiency of the drainage system.

The study revealed significant spatial variability in soil salinity across the studied fields. In the middle lands, where the drainage system was well-maintained and fully functional, soil salinity levels were effectively controlled. In fact, in some areas, the soil electrical conductivity (ECe) was observed to be lower than the salinity of the irrigation water. This highlights the efficiency of the drainage system in preventing salt accumulation and maintaining favorable conditions for crop growth.

Conversely, in the marginal lands, where drainage relied solely on main ditches and lacked an integrated network of field drains, soil salinity levels were notably higher. This discrepancy between middle and marginal lands indicates the need for targeted drainage interventions in underperforming areas to enhance salinity control and ensure uniform field conditions.

Drainage water salinity showed a cumulative increase in downstream sections of the drainage network, with salinity levels in the collectors (P1 and P2) stabilizing around 20 dS/m and in the main drainage ditch (P3) reaching approximately 33 dS/m. Temporal analysis of the drainage water salinity indicated steady or quasi-steady conditions, reflecting the drainage system's long-term operation in the region. The stability of these values over time suggests that the system has reached a dynamic equilibrium, with consistent salt removal from the soil profile.

Implications for Drainage Management and Agricultural Practices

The findings of this study underscore the critical role of drainage systems in managing soil salinity in irrigated agricultural lands. The effectiveness of these systems is closely tied to their design, maintenance, and integration with irrigation management practices. Key recommendations based on this study include the following:

Enhancing Drainage Coverage: Marginal lands with inadequate drainage networks require the extension of field drains or improvements to existing infrastructure to achieve better salinity control.

Monitoring and Calibration: Regular monitoring of soil salinity using indirect methods, such as ECa measurements, is essential for identifying problematic areas and optimizing drainage system performance. Calibrating these measurements to local soil and water conditions will improve the accuracy of salinity assessments.

Balancing Irrigation and Drainage: Efficient irrigation management, coupled with effective drainage, is crucial for minimizing salt buildup in the root zone. Adjustments in irrigation scheduling and water quality monitoring can help maintain soil salinity within acceptable limits.

Promoting Adaptive Management: Given the dynamic nature of salinity processes, adaptive management strategies that incorporate real-time monitoring data and predictive models are recommended. These strategies should focus on mitigating risks associated with soil and water salinity, especially under changing climatic and hydrological conditions.

Conclusion:

This study highlights the importance of using a combination of traditional sampling, laboratory analysis, and advanced geophysical methods to assess the performance of drainage systems in controlling soil salinity. The integration of ECa measurements with soil salinity data provided valuable insights into the spatial variability of salinity and the impact of drainage systems on soil health. The results emphasize the need for targeted drainage interventions in underperforming areas, as well as the adoption of adaptive management practices to enhance agricultural sustainability in saline environments.

By addressing the specific challenges of soil and water salinity, the findings of this research contribute to the broader goal of improving land productivity and ensuring long-term sustainability in irrigated agriculture. Future studies should explore the integration of remote sensing technologies with field measurements to further enhance the efficiency and scalability of salinity assessment and management approaches.

Author Contributions:

All authors are contributing in data collection, analysis and performing the article.

Data Availability Statement:

Raw data were generated at National Salinity Research Center (NSRC). Derived data supporting the findings of this study are available from the corresponding author Farhad Dehghani, Ph.D., on request after the permission of the NSRC.

Acknowledgements:

The authors would like to thank the Deputy of Agro-Water and Soil of the Ministry of Agriculture-Jahad for project providing funding. 

Ethical considerations:

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest:

The author declares no conflict of interest.