انتخاب‌پذیری ذرات خاک تحت‌تأثیر خصوصیات جریان در فرسایش شیاری

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم و مهندسی خاک دانشکده کشاورزی دانشگاه زنجان، زنجان، ایران

2 گروه علوم و مهندسی خاک-دانشکده کشاورزی-دانشگاه زنجان- زنجان- ایران

چکیده

فرسایش شیاری از اشکال مهم فرسایش آبی در دامنه­های تحت کشت می­باشد. شیارها مسیرهای جریان هستند که در اثر تمرکز جریان روی دامنه به وجود آمده و هدررفت خاک در آنها زیاد است. مقدار و نوع ذرات منتقله از شیارها یا انتخاب­پذیری ذرات تحت‌تأثیر عوامل گوناگون به­ویژه شدت جریان می­تواند قرار بگیرد. این پژوهش به‌منظور بررسی فرسایش شیاری و انتخاب­پذیری ذرات تحت‌تأثیر خصوصیات جریان انجام گرفت. آزمایش­های صحرایی در کشت­زاری دیم با شیب 10 درصد در شیارهای با طول شش متر تحت شدت­های مختلف جریان (2، 5/2، 3، 5/3 و 4 لیتر بر دقیقه) در قالب طرح بلوک کامل تصادفی با سه تکرار انجام شد. اندازه­گیری­ها با استفاده از جریانی با شدت 3 لیتر بر دقیقه در بازه­های زمانی 5 دقیقه به مدت 60 دقیقه انجام گرفت و دانه­بندی ذرات در کنار خصوصیات جریان در هر یک از شدت­های جریان تعیین شد. بر اساس نتایج، همبستگی معنی­داری بین شدت جریان و سایر خصوصیات جریان (سرعت جریان، قدرت جریان و تنش برشی)، فرسایش شیاری و انتخاب­پذیری ذرات وجود داشت. با افزایش شدت جریان، سایر خصوصیات جریان (سرعت جریان، قدرت جریان و تنش برشی) بیشتر شد و افزایش مقدار فرسایش شیاری را به دنبال داشت. همچنین انتخاب­پذیری ذرات رس و شن بیشتر شد، درحالی‌که انتخاب­پذیری ذرات سیلت کاهش یافت. سیلت حساس­ترین ذره به انتقال به‌وسیله جریان متمرکز بود؛ به­طوری که جریان­های با تنش برشی ضعیف نیز امکان انتقال آنها را داشتند. این پژوهش نشان داد که شدت جریان، مؤلفه مهم جریان در افزایش مقدار فرسایش شیاری و انتخاب­پذیری ذرات خاک است. 

کلیدواژه‌ها


عنوان مقاله [English]

The Selectivity of Soil Particles in Relation to Flow Characteristics in Rill Erosion

نویسندگان [English]

  • Ali Reza Vaezi 1
  • Leila Varghaei 2
1 Soil Science Department, Agriculture Faculty, University of Zanjan, Zanjan, Iran-
2 Soil Science Department, Agriculture Faculty, University of Zanjan, Zanjan, Iran-
چکیده [English]

Rill erosion is an important form of water erosion on cultivated slopes. Rills are flow paths that are created by concentrated flow on hillslope and causes higher rates of soil loss. The amount and type of particles transferred through the rills or the selectivity of the particles may be affected by various factors, especially the flow rate. This study was conducted to investigate the rill erosion and the particle selectivity under the flow characteristics. Field experiment was done in a rainfed land with a slope gradient of 10% in the rills/furrows with 6 m in long under different flow intensities (2, 2.5, 3, 3.5 and 4) using a randomized complete block with three replications. Field measurements were performed using a flow rate of 3 lit min-1 at intervals of 5-min for 60 min. Rill erosion and the particle selectivity were determined along with flow characteristics for various flow intensities. Significant correlations were found between flow intensity and flow characteristics (velocity, shear stress and power), rill erosion and the selectivity of particles. With an increase in flow rate, flow characteristics increased in the rills and enhanced rill erosion as well as the selectivity of sand and clay, whereas the selectivity of silt decreased in the rills. Silt showed the highest sensitivity to selection by concentrated flow, so that flows with lower shear stress could erode it from the rills. Wholly, this study revealed that the flow rate is the most flow characteristics influencing rill erosion and the selectivity of soil particles. 

کلیدواژه‌ها [English]

  • Particle size distribution
  • Shear stress
  • Concentrated flow
  • Flow rate
  • Flow power
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