بررسی مقاومت مکانیکی خاک تحت سطوح مختلف تیمارهای تراکم و سیمانی شدن و تأثیر توسعه ریشه ذرت و گندم بر آن در شرایط آزمایشگاهی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری، گروه علوم و مهندسی خاک، دانشکده مهندسی و فناوری کشاورزی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، کرج، ایران

2 دانشیار گروه علوم و مهندسی خاک، دانشکده مهندسی و فناوری کشاورزی، دانشکدگان کشاورزی و منابع، دانشگاه تهران، کرج، ایران

3 استاد گروه علوم و مهندسی خاک، دانشکده مهندسی و فناوری کشاورزی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، کرج، ایران

10.22059/ijswr.2022.335187.669152

چکیده

افزایش مقاومت مکانیکی خاک از طرفی سبب مستحکم­تر شدن خاک و ثبات آن در برابر عوامل بیرونی می­شود و از طرفی سبب محدودیت توسعه ریشه و فرایند جذب آب توسط ریشه از خاک اطراف آن می­گردد. در این مطالعه محدودیت­ها و مزایای احتمالی ناشی از مقاومت مکانیکی خاک در وضعیت بهینه رطوبتی بررسی شد. از دو عامل تراکم و سیمانی کردن به‌منظور افزایش مقاومت به فروروی خاک مرطوب استفاده شد و برای جلوگیری از اثرات نوسان رطوبت بر مقاومت مکانیکی اولیه خاک، از سامانه تثبیت مکش استفاده شد تا رطوبت خاک در مکش ماتریک 40 سانتی­متر (معادل با تخلخل تهویه­ای 10 درصد) تثبیت گردد. 132 واحد آزمایشی (گلدان) در سطوح مختلف تیمارهای تراکم (جرم مخصوص ظاهری معادل با 52/1، 56/1، 6/1، 66/1، 69/1 و 71/1 مگاگرم بر مترمکعب) و سیمان (سیمان اضافه شده معادل با صفر، 3/0، 6/0، 9/0، 2/1 و 5/1 درصد جرمی) اقدام به کشت گیاهان ذرت و گندم شد تا اثر احتمالی توسعه ریشه بر افزایش مقاومت مکانیکی اولیه خاک در قالب یک آزمایش فاکتوریل و طرح کامل تصادفی تعیین گردد. نتایج نشان داد که مقاومت مکانیکی خاک در اثر هر دو تیمار تراکم و سیمان از مقادیر کم تا مقادیر محدودکننده افزایش یافت و دامنه­ای از خاک­های سست تا مستحکم در اثر این دو تیمار ایجاد شد. مقاومت مکانیکی خاک در تیمار شاهد و برخی سطوح اولیه دو تیمار تراکم و سیمان در حد خاک­های سست قرار داشت ولی توسعه ریشه گیاه سبب شد استحکام خاک در تیمار شاهد و تراکم به مقدار قابل‌توجهی افزایش یابد. از طرفی توسعه ریشه سبب شد محدودیت خاک از نظر دردسترس‌بودن آب برای گیاه فراتر از حد بالای دامنه بحرانی (5/2 مگاپاسکال) قرار گیرد؛ بنابراین باتوجه‌به کارکرد مورد انتظار خاک، تغییرات مقاومت مکانیکی در اثر تراکم، سیمان و توسعه ریشه می­تواند به‌عنوان فرصت یا محدودیت عمل نماید.

کلیدواژه‌ها


عنوان مقاله [English]

Investigation of Soil Mechanical Resistance under Different Levels of Compaction and Cementation Treatments and the Effect of Maize and Wheat Root Development on It in Experimental Condition

نویسندگان [English]

  • Ehsan Ghezelbash 1
  • Mohammad Hosein Mohammadi 2
  • Mahdi Shorafa 3
1 Ph.D student, of Soil Science Department, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
2 Associated professor of Soil Science Department, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
3 Professor of Soil Science Department, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
چکیده [English]

Increasing the soil mechanical resistance firstly strengthens the soil and causes its stability against external factors, and on the other hand, restricts root development and the process of root water uptake from around soil. In this study, the limitations and possible benefits of soil mechanical resistance in an optimal moisture condition were investigated. Two factors of compaction and cementation were used to increase the soil mechanical resistance at wet soil and to prevent the effects of moisture fluctuation on the initial soil mechanical resistance, a suction buffer system was used to stabilize soil moisture at the matric suction of 40 cm (aeration porosity equal to 10%). 132 experimental units at different levels of compaction (bulk densities equal to 1.52, 1.56, 1.6, 1.66, 1.69, and 1.71 Mg.m-3) and cementation (added cement equal to 0, 0.3, 0.6, 0.9, 1.2 and 1.5 percentage) treatments, maize and wheat plants were cultivated to determine the possible effect of root development on increasing the initial soil mechanical resistance. The results showed that the soil mechanical resistance increased from low to restricting values due to both compaction and cementation treatments, and a range of loose to strong soils was created due to these two treatments. Soil mechanical resistance in the control treatment and some initial levels of the two compaction and cementation treatments were in the range of loose soils, but the root development caused a significant increase in soil strength in control and compacted treatments. On the other hand, root development caused the soil limitation in terms of soil water availability to exceed the critical limit (2.5 MPa). Therefore, according to the expected function of the soil, changes in mechanical strength due to compaction, cement, and root development can be considered as an opportunity or constraint.

کلیدواژه‌ها [English]

  • Threshold of soil mechanical resistance
  • water uptake
  • particle cementation
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