نوع مقاله : مقاله پژوهشی

نویسندگان

• مریم نوابیان ¹
• مصطفی جمشیدی اوانکی ²

¹ دانشیار گروه مهندسی آب، دانشکده علوم کشاورزی دانشگاه گیلان و عضو وابسته گروه آب و محیط زیست پژوهشکده حوضه آبی دریای خزر دانشگاه گیلان، گیلان، ایران.

² استادیار گروه مهندسی نساجی، دانشکده فنی دانشگاه گیلان، گیلان، ایران.

چکیده

اطلاع از وضعیت رطوبت خاک می‌تواند تاثیر بسزایی بر برنامه‌ریزی آبیاری و در نتیجه مدیریت آب بخش کشاورزی به عنوان بزرگ‌ترین مصرف‌کننده آب به همراه داشته باشد. اندازه‌گیری رطوبت خاک به روش بلوک‌ متخلخل مبتنی بر مقاومت‌سنجی جریان برق از جمله روش‌های اندازه‌گیری رطوبت است که توسعۀ دانش ساخت آن می‌تواند گام موثری در کاهش هزینه، افزایش دقت و سهولت اندازه‌گیری رطوبت و در نتیجه مدیریت مصرف آب کشاوری باشد. هدف از این پژوهش، بررسی خصوصیات الیاف شیشه‌ای حصیری بر دقت اندازه‌گیری رطوبت خاک به روش بلوک متخلخل است. در این راستا، از دو الیاف P200 و P186 در ساخت بلوک مبتنی بر سازۀ الیافی استفاده گردید و دقت اندازه‌گیری رطوبت توسط آن در 10 بافت خاک در سه تکرار بررسی شد. برای ارزیابی دقت بلوک‌ها، رطوبت اندازه‌گیری شده توسط آن‌ها با روش رطوبت وزنی مقایسه و شاخص‌های آماری R²، RMSE، nRMSE، MAE و D-index محاسبه شدند. نتایج نشان داد که بلوک‌های ساخته شده با هر دو الیاف دقت قابل قبول  در اندازه‌گیری رطوبت خاک دارند (R²=0.7-0.98، RMSE=0.05-0.07، nRMSE=16-20%، MAE=0.05-0.06 و D-index=0.94-0.95) اما الیاف P200 با خطای حدود 5 درصد،  دقت بیشتری به­دست داده است. این بلوک‌ها در بافت خاک متوسط با حداقل و حداکثر شن به­ترتیب 20 و 70 درصد و حداکثر رس 30 درصد، نسبت به سایر بافت‌ها دقت بیشتری (RMSE<0.06) نشان دادند. دقت بلوک‌ها در حد بالای رطوبت خاک کاهش یافت به‌طوری‌که در محدوده دقت 7 درصد قرار نگرفت. بنابراین، استفاده از آن‌ها برای دامنه رطوبت خاک 40-25 درصد وزنی پیشنهاد می‌شود.

کلیدواژه‌ها

• بافت خاک
• تراکم الیاف
• حسگر رطوبتی
• خیس‌شدگی الیاف

عنوان مقاله [English]

Effect of fiber-based Sensors Structure on Block Sensorein soil Moisture monitoring performance

نویسندگان [English]

• Maryam Navabian ¹
• Mostafa Jamshidi Avanaki ²

¹ Associated Prof. of Water Eng. Dep., Agricultural Sciences Faculty, University of Guilan and and Dept. of Water Eng. and Environment, University of Guilan, Rasht, Iran

² Assistant Professor of Fibrous Structures and Process Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran

چکیده [English]

Extended Abstract

Introduction

Knowledge of soil moisture status can significantly impact irrigation planning and, consequently, water management in the agricultural sector, which is the most expensive recipient of water resource allocation. Soil moisture measurement using the porous block method, based on electrical resistance measurement, is one of the techniques for assessing moisture levels. Developing an understanding of its construction can effectively reduce costs, increase accuracy, simplify moisture measurement, and achieve these goals. This study aims to enhance the understanding of soil moisture measurement through the development and assessment of porous blocks constructed with glass mat fibers, specifically P200 and P186 types.

Materials and Methods
In this regard, two types of glass fibers, P200 and P186, were used in the construction of a block with a fibrous structure. The accuracy of moisture measurement was then evaluated in 10 different soil textures. To prepare the soil, it was dried, pounded, and passed through a 2-mm sieve before being placed into a pot. After installing three replicates of each block in the pot, the soil was saturated. At various intervals until the soil dried, the electrical resistance of the block and the soil moisture were measured using the gravimetric method. To assess the accuracy of the blocks, the moisture readings from the blocks were compared with those obtained from the gravimetric method, and statistical indices such as R² (coefficient of determination), RMSE (root mean square error), nRMSE (normalized root mean square error), MAE (mean absolute error), and D-index (index of agreement) were calculated.

Results and Discussion
The results showed that ELE glass fibers absorbed 2.6 and 0.5 times more water than P200 and P186 fibers, respectively, over 180 seconds. A comparison of the fitting curves for the wicking behavior of the two fibers indicates that the quadratic curve provides a better fit than the linear curve. Additionally, the results showed that solution absorption in P186 decreased earlier than in P200. Therefore, it appears that P200 fibers are more effective at absorbing the solution and, subsequently, the water from the soil environment. The results also indicated that ELE and P200 fibers exhibited a similar decreasing trend in moisture over the first 15 minutes; however, after that point, the moisture reduction rate in P200 continued at a lower slope. P200 fibers demonstrated behavior more akin to ELE fibers during both moisture reduction and solution absorption. The findings reveal that the porous blocks constructed with P200 fibers achieved superior accuracy in measuring soil moisture, yielding an error margin of approximately 5%. Notably, the findings indicate that the P186 and P200 fibers exhibit optimal accuracy in medium soil textures, outperforming their performance in other soil types. Specifically, the P186 fibers achieve their highest accuracy in soil textures characterized by a sand content between 50-70% and clay content below 35%. Similarly, the P200 fibers also demonstrate robust accuracy within the same sand and clay content ranges, but they extend their effectiveness to include soils with sand content ranging from 20-50% and clay content around 28%. Conversely, the results suggest that both P200 and P186 fibers struggle with accuracy in soil textures that exhibit either high clay or high sand content. This highlights the importance of soil composition in the performance of these fibers for measuring soil moisture, indicating that they are less reliable in extreme soil conditions. Furthermore, the study highlighted a decline in measurement accuracy at elevated soil moisture levels, indicating that these blocks are most effective within a soil moisture range of 25-40% by weight.

Conclusion
In conclusion, this research underscores the potential of utilizing glass mat fibers in the construction of porous blocks to improve soil moisture measurement accuracy. By refining this methodology, the findings contribute valuable insights toward optimizing irrigation practices and advancing water management strategies in agriculture. Enhanced accuracy in moisture readings not only promotes efficient water usage but also supports sustainable agricultural practices, ultimately benefiting food production and environmental conservation efforts.

کلیدواژه‌ها [English]

• Fiber Density
• Moisture Sensor
• Soil Texture
• Wetting of Fiber