نوع مقاله : مقالات پژوهشی
نویسندگان
1 گروه مهندسی طبیعت، دانشکده کشاورزی شیروان، دانشگاه بجنورد، ایران
2 دانشکده کشاورزی، دانشگاه شهید باهنر کرمان
چکیده
روش‌های نوین آبیاری در سطح مزرعه راهکاری کاربردی در مدیریت معضل کاهش منابع آب شیرین است. در بحث مدیریت منابع آب، نیاز به برآورد پارامترهای هیدرولیکی- فیزیکی خاک می‌باشد. در این پژوهش، با هدف مطالعه میزان کارایی الگوریتم لونبرگ – مارکواردت، به ارزیابی جریان غیراشباع آب تحت روش آبیاری سنتر پیوت، انتقال و آبشویی نیترات در سطح مزرعه یونجه چهار ساله در مدل HYDRUS-3D پرداخته شد. در این تحقیق پارامترهای حاکم بر میزان نفوذپذیری آب و انتقال املاح با استفاده از الگوریتم لونبرگ – مارکواردت در شرایط واقعی برآورد گردید. به منظور شبیه‌سازی روند تغییرات غلظت نیترات و آمونیوم در امتداد ستون خاک از ضریب جذب فروندلیچ بهره گرفته شد. نتایج شبیه‌سازی HYDRUS-3D، بیانگر دقت مدل در شبیه‌سازی جریان آب باcm3.cm-3 0057/0 = RMSE (خطای ریشه میانگین مربعات) و 98/0= NSE (ناش-ساتکلیف) و 98/0= NSE در لایه سطحی، و cm3.cm-3 0049/0= RMSE و 99/0= NSE در لایه عمقی خاک بود. میزان دقت مدل در بررسی روند تغییرات نیترات خاک نیز در دو لایه سطحی و عمقی به ترتیب برابر باcm3.cm-3 009/0= RMSE و 008/0 = RMSEبه دست آمد. همچنین در این تحقیق به بررسی روند جذب نیترات توسط گیاه طی چهارسال پرداخته شد که روند تغییرات بیانگر افزایش جذب نیترات در گیاه بود. براساس نتایج حاصله می‌توان ذکر نمود که الگوریتم لونبرگ – مارکواردت به‌خوبی توانسته روند تغییرات پارامترها را در مدل HYDRUS-3D تحت روش آبیاری سنترپیوت شبیه‌سازی نماید. از این رو می‌توان بیان نمود الگوریتم لونبرگ – مارکواردت قادر به برآورد تغییرات پارامترها تحت روش‌های نوین آبیاری حتی در مدل‌های چند بعدی نیز می‌باشد.
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
Study of Water Flow and Nitrate Transport under Center Pivot Irrigation Using the HYDRUS-3D Model.
نویسندگان [English]
- Vahidreza Jalali 1
- Samaneh Etminan 2
1 Department of Nature Engineering, Shirvan Faculty of Agriculture, University of Bojnord, Iran
2 , Faculty of Agriculture, Shahid Bahonar University of Kerman, Iran
چکیده [English]
Introduction
Climate change and drought events over the past decades have led to a decrease in surface and groundwater resources, particularly fresh water sources. On the other hand, the global population growth rate is increasing, which has resulted in a rising demand for food. One of the essential pillars of food security is providing adequate water resources for agricultural use. Therefore, in recent years, water resource management through various methods to enhance efficiency has been recognized as both a management and research challenge. Among the proposed management strategies is the use of saline water alongwith fresh water, combined with modern irrigation techniques at the farm scale. In this study, the impact of the center-pivot irrigation method using saline water sources on alfalfa farm performance over four consecutive years has been investigated. The effect of this management approach was analyzed using the HYDRUS-3D model, focusing on plant growth and yield, soil moisture variations, leaching rates, and nitrate accumulation within the farm.
Materials and Methods
In this study, a four-year-old alfalfa farm at Birjand University, covering an area of 3 hectares and irrigated using the center-pivot method, was selected. A one-meter-deep soil profile was excavated to examine changes in the soil's physical and chemical properties over time. Soil moisture was measured using Time Domain Reflectometry (TDR) at different depths and various irrigation intervals to assess root-zone moisture dynamics. Since the soil in the study area was deficient in organic matter, soil samples were collected before planting alfalfa. To ensure adequate phosphorus levels, diammonium phosphate fertilizer was applied during the tillering stage. Ammonium and nitrate concentrations were also analyzed by collecting soil samples at different depths over various periods and measuring them using a spectrophotometer. The Levenberg-Marquardt optimization algorithm was employed to estimate hydraulic parameters and solute transport characteristics. To model changes in ammonium and nitrate levels in the soil, the Freundlich adsorption coefficient was applied. For simulating variations in soil moisture, ammonium, nitrate, and plant growth trends in the second and fourth years, the HYDRUS-3D hydraulic model was utilized.
Results and Discussion
The accuracy and efficiency of the HYDRUS-3D model in analyzing soil variations in terms of water flow and solutes transport were assessed using two statistical indices: RMSE (Root Mean Square Error) and NSE (Nash-Sutcliffe Efficiency). The RMSE values Of calibration for soil moisture variations at three studied depths (0-40 cm, 40-60 cm, and 60-100 cm) were 0.0057, 0.0049, and 0.0044 cm3.cm-3 , respectively. The NSE values at these depths during the calibration phase were 0.91, 0.98, and 0.99, respectively. For the validation phase, the RMSE and NSE values at 0-40 cm were 0.0021 and 0.97 cm3.cm-3 , at 40-60 cm were 0.0038 and 0.99, and at 60-100 cm were 0.0029 and 0.99, respectively. Based on the results, the efficiency of the Levenberg-Marquardt optimization algorithm and the capability of the HYDRUS-3D model in simulating soil moisture dynamics in the plant root zone under center-pivot irrigation were verified. The RMSE values for ammonium simulation at the three depths during validation were 0.0055, 0.0003, and 0.0008 mg.l, while the NSE values were 0.97, 0.99, and 0.99, respectively. For nitrate concentration analysis at the same depths, the RMSE values were 0.009, 0.009, and 0.008 mg.l, while the NSE values were 0.99, 0.98, and 0.99, respectively. These findings confirm the effectiveness of the HYDRUS-3D model in estimating solute variations in soil. However, accuracy decreased with depth due to soil heterogeneity and unsaturated conditions, as the model assumes a homogeneous environment. Nitrate accumulation in plants showed an increasing trend as the plant growth period was increased. The measured nitrate concentration in two-year-old alfalfa was significantly lower than that in four-year-old alfalfa. Additionally, nitrate accumulation in the root zone of four-year-old plants was higher than the younger ones. This process is influenced by fertilization practices and the expansion of the root system in the fourth year, which enhances nutrient uptake efficiency.
Conclusion
Based on the statistical indices obtained from the simulation of soil variations using the HYDRUS-3D model compared to measured values, it can be concluded that the Levenberg-Marquardt optimization algorithm has provided an accurate and practical estimation of soil hydraulic parameters under the applied management conditions. Furthermore, the HYDRUS-3D model has effectively simulated long-term variations over a four-year period within this management framework. Therefore, both the optimization algorithm and the HYDRUS-3D model demonstrate sufficient capability for assessing soil moisture dynamics and solute variations under modern irrigation management techniques at the farm scale. These methods can serve as powerful tools for formulating management strategies and evaluating the outcomes of different irrigation practices.
کلیدواژه‌ها [English]
- Hydrous model
- Modern irrigation
- reverse solution
- soil salts
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