اثر سیستم آبیاری و سطح کود نیتروژن بر توزیع نیترات در خاکرخ با استفاده از تکنیک ردیابی ایزوتوپ نیتروژن-15

نوع مقاله : کاربردی

نویسندگان

1 دانش‌آموخته کارشناسی ارشد گروه علوم خاک، دانشگاه شاهد، تهران، ایران

2 دانشیار گروه علوم خاک، دانشگاه شاهد، تهران، ایران

10.22055/agen.2021.35100.1585

چکیده

به‌منظور بررسی تاثیر سیستم آبیاری و سطح کود نیتروژن بر الگوی توزیع نیترات در اعماق خاک، آزمایشی در قالب طرح بلوک‌های کامل تصادفی، به‌صورت کرت‌های دو بار خرد شده در سه تکرار در مزرعه پژوهشکده کشاورزی هسته-ای تحت کشت گوجه‌فرنگی انجام شد. سیستم‌های آبیاری جویچه‌ای و قطره‌ای (فاکتور اصلی)، تیمار کودی (100 و 200 Kg ha-1) از منبع کود اوره (فاکتور فرعی اول) و عمق نمونه‌برداری( 15، 30 و60 سانتی‌متر)، (فاکتور فرعی دوم) بودند. جهت ردیابی نیتروژن، از کود اوره نشاندار استفاده شد. سه عصاره‌گیر در اعماق 15، 30 و 60 سانتیمتر در کرتچه ایزوتوپی نصب و عصاره‌گیری صورت گرفت. غلظت نیترات محلول خاک توسط دستگاه اسپکتروفتومتر و نسبت ایزوتوپی نیتروژن-15 به نیتروژن-14، توسط دستگاه اسپکترومتر جرمی اندازه‌گیری شد. نتایج نشان داد مقدار نیترات در سیستم کودآبیاری قطره‌ای و آبیاری جویچه‌ای در سطح کود 100 کیلوگرم در هکتار و عمق 60 سانتی‌متر به‌ترتیب 73/1 و 90/44 میلی‌گرم در لیتر بود. از مجموع نیتروژن نیتراتی موجود در لایه 60-0 سانتی‌متر در سیستم کودآبیاری قطره‌ای(62، 29 و 9 درصد) و آبیاری جویچه‌ای(10، 34 و 56 درصد)، به‌ترتیب در اعماق 15، 30 و 60 سانتی‌متر مشاهده شد. داده‌های نیتروژن-15 نشان داد که از مجموع نیتروژن نیتراتی در سیستم کودآبیاری قطره‌ای (20 و 80 درصد) و آبیاری جویچه‌ای، (77 و 23 درصد) به‌ترتیب از منبع کود نشاندار نیتروژن-15 و منبع خاک بود. سیستم کودآبیاری قطره‌ای و سطح کودی 100 کیلوگرم نیتروژن در هکتار، به‌عنوان بهترین روش آبیاری و بهترین سطح کودی مناسب از جهت کاهش تلفات آبشویی نیترات در شرایط این تحقیق بود.

کلیدواژه‌ها


عنوان مقاله [English]

Effect of Irrigation System and Nitrogen Fertilizer Level on Nitrate Distribution in Soil Using Nitrogen-15 Isotope Tracking Technique

نویسندگان [English]

  • Ali Khorasani 1
  • abdolamir Bosatni 2
1 M.Sc. Graduate, Department of Soil Science, Shahed University, Tehran, Iran
2 Associate Professor, Department of Soil Science, Shahed University, Tehran, Iran
چکیده [English]

Assessment of Irrigation System and Nitrogen Fertilizer Level on Nitrate Distribution in Soil Using Nitrogen-15 Isotope Tracking Technique

Introduction: Soil contamination is the presence, diffusion or fusion of foreign matter into the soil, altering its physical and chemical quality in a manner that is harmful to humans, plants and the environment. Soil nitrate pollution due to excessive use of nitrogen fertilizer and inappropriate irrigation causes nitrate accumulation under the active root zone and its movement to groundwater and endangers the environment. By labelling the soil with 15N-labelled nitrate or urea it is possible to trace the fate of fertilizer derived nitrate down the soil profile. This can be achieved by taking sequential by using suction cups to sample the nitrate in the soil solution. The purpose of this study was to investigate the effect of irrigation system and nitrogen fertilizer level on the amount and pattern of nitrate distribution in different soil depths.
Materials and Methods: The experiment was conducted in a randomized complete block design with a split plot in two plots and three replications on tomato plant in Agricultural Research Farm of Nuclear Science and Technology Research Institute. Furrow and drip irrigation systems as the main factor and fertilizer treatment (100 and 200 kg N/ha from urea fertilizer source), soil depths (including 15, 30 and 60 cm) and sampling time (Includes 28, 40, 61 and 80 days after plantin) were first, second and third sub-factors respectively. In order to trace nitrogen, CO(15NH2)2 urea fertilizer with enrichment of 4.634% was used. Three soil solution extractors were installed at depths of 15, 30 and 60 cm in each isotopic plot in each replication and extraction was performed 4 times. Soil solution nitrate and 15N/14N isotope ratio were measured by spectrophotometer and mass spectrometer respectively.
Results and Discussion: The highest soil nitrate-N (N-NO3) concentration(94.31 mg L-1) in furrow irrigation (Fertilizer level of 200 kg N ha-1, soil depth of 60 cm and third time of soil solution sampling) and its lowest concentration(1.73 mg l-1) in drip fertigation system (fertilizer level of 100 kg N ha-1, soil depth of 60 cm and fourth time of soil solution sampling) was observed. The results showed that the concentration of nitrate-N in the drip fertigation system was higher at a depth of 15 cm (active root depth) than at depths of 30 and 60 cm. The highest concentration of nitrate nitrogen derived from the source of nitrogen-15 (N-15NO3 dff)(88.82 mgl-1) in furrow irrigation (Fertilizer level of 200 kg N ha-1, soil depth of 60 cm and third time of soil solution sampling) and the lowest concentration (0.12 mgl-1) in drip irrigation fertilizer (fertilizer level of 100 kg N ha-1, soil depth of 30 cm and second time of soil solution sampling) was observed. Nitrate-N concentration derived from labeled fertilizer source in furrow irrigation at a depth of 60 cm (below the active root depth in furrow irrigation) was greater than the depths of 15 and 30 cm. the results also showed that The highest concentration(42.25 mgl-1) of nitrate-N derived from soil source in drip fertigation system (fertilizer level of 200 kg N ha-1, soil depth of 15 cm and first time of soil solution sampling) and the lowest concentration (0.29 mgl-1) in drip fertigation system (100 kg N ha-1, soil depth of 60 Cm and the fourth time of soil solution sampling) was observed.
Conclusion: The results showed that of the total nitrate nitrogen in the 0-60 cm depth, the values (62, 29 and 9%) in the drip and (10, 34 and 56%) in the furrow irrigation system in Depths of 15, 30 and 60 cm were observed respectively. Nitrogen-15 data showed that of the total soil nitrate nitrogen, the values of 20 and 80 percent in fertigation system and 77 and 23 percent in furrow irrigation system was observed from labeled fertilizer and soil source, respectively. increasing nitrate accumulation was observed in soil depth of 60 cm with increasing nitrogen application in furrow irrigation. The use of fertigation system was effective to prevent nitrogen loss from the active root zone of the plant. In general, fertigation system and fertilizer level of 100 kg N ha-1 was the best irrigation method and the best fertilizer level to reduce nitrate leaching losses in the conditions of this study.

کلیدواژه‌ها [English]

  • *Nitrogen-labeled fertilizer-15*
  • *Suction cup*
  • *Drip irrigation*
  • *Nitrate leaching*