تأثیر ضربه قطرات باران بر هدررفت خاک از نوار‌های کشت در خاک‌های با بافت مختلف

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه خاکشناسی، دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران

2 گروه خاکشناسی، دانشکده کشاورزی، دانشگاه زنجان، شهر زنجان، ایران

چکیده

ضعف پوشش گیاهی روی سطح و محتوای اندک ماده آلی خاک از عواملی هستند که حساسیت خاک­های مناطق نیمه­خشک به فرسایش خاک در نوارهای کشت را افزایش می­دهند. این پژوهش با هدف بررسی اثر ضربه قطرات باران بر رواناب و هدررفت خاک از شیارها در خاک‌های با بافت مختلف در منطقه نیمه‌خشک اجرا شد. نمونه­های خاک از بافت­های غالب خاک­ در دامنه­های تحت فرسایش شیاری در استان زنجان تهیه شدند. برای این منظور، سه خاک با بافت مختلف ( لوم‌رسی، لوم‌سیلتی و لوم‌شنی) در فلومی به طول 1 متر و عرض 6/0 متر با سه تکرار در شیب یکنواخت 10 درصد تحت باران شبیه‌سازی شده بررسی شدند. هر یک از خاک‌ها در دو حالت بارندگی: زیر ضربه مستقیم قطرات و بدون ضربه قطرات باران تحت بارانی با شدت 50 میلی‌متر در ساعت به مدت 30 دقیقه قرار گرفتند. تولید رواناب و هدررفت خاک از شیارها در زمان­های مختلف اندازه­گیری شد. نتایج نشان داد تولید رواناب و هدررفت خاک تحت تأثیر ضربه قطرات باران قرار گرفت ( 01/0p <). بیش­ترین و کم­ترین تأثیر ضربه قطرات باران بر تولید رواناب به­ترتیب در خاک لوم‌رسی ( 95/2 برابر) و لوم‌شنی (02/2 برابر) بود. از نظر هدررفت، خاک لوم‌شنی حساس‌ترین خاک به اثر ضربه قطرات باران (66/3 برابر) و خاک لوم‌رسی مقاوم‌ترین ( 47/2 برابر) بود. تولید رواناب طی زمان در شیارها تحت ضربه قطرات باران از روند افزایشی پیروی کرد در حالی که تغییرات زمانی هدررفت خاک الگوی نامنظمی داشت. این مطالعه نشان داد که تولید رواناب در شیارها تحت بارندگی به شدت تحت تأثیر توزیع اندازه ذرات خاک است در حالی که هدررفت خاک از شیارها به پایداری ساختمان خاک وابسته است. بنابراین نگهداری پوشش سطح خاک نقشی مؤثر در جلوگیری از هدررفت خاک از شیارها تحت بارندگی دارد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The Effect of Raindrops Impact on Soil Loss from Cultivated Farrows in Different Soils

نویسندگان [English]

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

Poor vegetation cover on the surface and lower content of soil organic matter are main factors influencing the sensitivity of soils to erosion from cultivation strips in semi-arid regions. The aim of this study was to investigate the effect of raindrops impact on runoff and soil loss from rills in different soil textures in the semi-arid region. Soil samples were taken from dominant soil textures in hillslopes affected by rill erosion in Zanjan province. For this purpose, three soils with different textures (clay loam, silty loam and sandy loam) were examined with three replications in a flume with 1 m in length and 0.6 m in width and 10% slope under simulated rainfall. Each soil sample was subjected under direct and non-direct raindrop impact with an intensity of 50 mm/h for 30 minutes. Runoff production and soil loss from the rills were measured at a time-scale of 5-min to reach a steady state runoff flow. The results showed that runoff production and soil loss were affected by raindrop impact (p < 0.01). The highest and the lowest impact of raindrops on runoff production were found in clay loam (2.95 times) and sandy loam (2.02 times), respectively. In terms of soil loss, sandy loam was the most sensitive to raindrop impact (3.66 times), whereas clay loam was the most resistant soil (2.47 times) to raindrop impact. An increasing trend was observed in runoff production during rainfall time, while soil loss varied irregularly in the rills. This study revealed that runoff production is significantly affected by the distribution of particle size, while soil loss is remarkably dependent on the aggregate stability. Therefore, maintaining soil surface cover plays an effective role in preventing soil loss by raindrop impact in the rainfed furrows.

کلیدواژه‌ها [English]

  • Rill detachment
  • . Runoff
  • rainfall intensity
  • soil physical properties
  • Soil loss
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