نوع مقاله : مقالات پژوهشی
نویسندگان
1 شهید چمران اهواز
2 اهواز
چکیده
خاک از جمله منابع طبیعی دیر تجدید شونده است که تخریب و یا حفاظت آن بستگی به نحوه استفاده و مدیریت اراضی دارد. مدیریتهای زراعی مختلف تأثیرات متفاوتی بر شاخصهای کیفی خاک میگذارند. در این تحقیق اثر مدیریتهای زراعیهای مختلف بر برخی از شاخصهای فیزیکی کیفیت خاک شامل مقدار مواد آلی، تخلخل، جرم مخصوص ظاهری، پایداری خاکدانه، ظرفیت آب قابل دسترس، مقاومت فروروی، هدایت هیدرولیکی اشباع و شیب منحنی رطوبتی در نقطه عطف) مورد بررسی قرار گرفت. بدین منظور سه مزرعه با مدیریتهای زراعی مختلف شامل سیستم تک کشتی-حذف بقایای گیاهی، تناوب زراعی- حذف بقایای گیاهی و تک کشتی-حفظ بقایا گیاهی در سطح انتخاب شدند. آزمایشی در قالب طرح آماری بلوکهای تصادفی با چهار تکرار صورت گرفت. نتایج تجزیه و تحلیل واریانس نشان داد که نوع مدیریت زراعی در سطح احتمال یک درصد بر همه پارامترهای فیزیکی مورد مطالعه اثر معنیدار داشت. نتایج مقایسه میانگین نشان داد که در روش مدیریت زراعی تک کشتی- حذف بقایای گیاهی، مقدار جرم مخصوص ظاهری (31/1 گرم بر سانتیمتر مکعب) و مقاومت فروروی خاک (40/0 مگاپاسکال) بیشتر از تیمارهای دیگر بود، در حالیکه بیشترین مقدار مواد آلی (038/1 %)، تخلخل (7/55 درصد)، میانگین وزنی قطر خاکدانه (04/1 میلیمتر)، شاخص پایداری خاکدانهها (28 درصد)، ظرفیت آب قابل دسترس (15/0 درصد)، هدایت هیدرولیکی اشباع (17/46 سانتیمتر بر ساعت) و شیب منحنی رطوبتی در نقطه عطف (053/0) در تیمار سیستم تک کشتی-با حفظ بقایای گیاهی مشاهده شد. به طور کلی نتایج این پژوهش نتایج نشان داد که سیستم تک کشتی-با حفظ بقایا گیاهی در افزایش کیفیت فیزیکی خاک نقشی بسزایی دارد.
کلیدواژهها
عنوان مقاله [English]
Effect of Different Agronomic Management on Some Physical Indicators of Soil Quality
نویسندگان [English]
- Arsalan Sadeghian 1
- gholamabbas sayyad 2
- Ahmad Farrokhian Firouzi 1
- Mojtaba Norouzi Masir 1
1 Shahid Chamran University of Ahvaz
2
چکیده [English]
Introduction: Soil is one of the renewable natural resources that take a long time to get renewed; its destruction or conservation depends on how land is used and managed. Soil quality refers to soil capacity in maintaining biological fertility, sustainability in plant production and yield. Maintaining soil quality is essential for sustainable food production and decomposition of organic wastes. Different agronomic managements have various effects on soil quality indicators. There are few published researches about the effect of various agronomic managements on soil quality indices in arid and semi-arid regions (such as Iran). Therefore, this study was conducted to investigate and compare the effects of three different agronomic management including crop rotation-crop residue removal, monoculture-crop residue removal and monoculture-crop residue retention systems on some physical indicators of soil quality.
Materials and Methods: In this research, three farms with three crop management systems including crop rotation-crop residue removal, monoculture-crop residue removal and monoculture-crop residue retention (10 ton per hectare) systems were investigated. In the monoculture-crop residue removal treatment, wheat was continuously cultivated for 8 years. In the rotation-crop residue removal system, wheat - mung bean were cultivated in rotation for 2 years. For the monoculture-crop residue retention system, wheat was planted for 10 years, after which the post-harvest residues were mixed with topsoil (0-15 cm). One hundred twenty soil samples (40 samples from each field) were prepared by systematic sampling from 0 to 15 cm depth. In order to investigate the effect of different agronomic management on soil physical quality, some indicators including soil organic matter, total porosity, bulk density, mean weight diameter of aggregates, aggregate stability, available water capacity, penetration resistance, saturated hydraulic conductivity, and slope of retention curve at inflection point (S-index) were measured. The experiment was conducted in a randomized complete block design with four replications. Also, the mean comparison was performed using Duncan's multiple range test.
Results and Discussion: The results of analysis of variance showed that the type of crop management had a significant effect (p<0.01) on organic matter, total porosity, bulk density, mean weight diameter of aggregates, aggregate stability, available water capacity, penetration resistance, saturated hydraulic conductivity and S-index. The results of mean comparison indicated that the monoculture-crop residue removal system resulted in a significant increase in bulk density (1.31 g cm-3) and soil penetration resistance (0.4 MPa) than other systems, while the highest organic matter content (1.038 %), porosity (55.7%), mean weight diameter (1.04 mm), aggregate stability index (28%), available water capacity (0.15%), saturated hydraulic conductivity (46.17 cm h-1) and S-index (0.053) was observed in the monoculture-crop residue retention system. The most measured values for soil quality indicators were more in monoculture-crop residual retention system compared with the other treatments. The amount of S-index of soils under monoculture-crop residual retention, crop rotation-crop residues removal, and monoculture-crop residual removal systems were 0.053, 0.032 and 0.019, respectively. The high S-index value of soil under monoculture-crop residual retention system can be attributed to its suitable amount of soil organic carbon and better soil structural quality. By contrast, in monoculture-crop residue removal system, elimination of organic matter had undesirable effect on soil porosity, and aggregate stability. Furthermore, the S-index values of the soils under crop rotation-crop residues removal, and monoculture-crop residual removal systems are below the Dexter’s soil quality index threshold (0.035); therefore, the results indicated that the soils are degraded.
Conclusion: The results of this study showed that crop management plays an important role in changing soil physical quality indicators. Among the studied crop managements, monoculture-crop residue retention management system showed more positive effects on soil physical parameters than the others. Retention of crop residues on soil surface increases the soil organic matter which in turn has positive effects on soil properties such as aggregate stability, saturated hydraulic conductivity, available water content and slope of retention curve at the inflection point. On the other hand, the monoculture-crop reside removal treatment, with less soil organic matter, had more undesirable effects on agronomic soils than other treatments. Based on the results, the effect of different agronomic management systems on improving soil physical quality indexes was in the following order: monoculture-crop residue retention >crop rotation-crop residue removal > monoculture-crop residue removal. According to the results, it can be concluded that soil organic matter is the central index of soil quality, which is intensely influenced by crop management system. Therefore, in arid and semiarid areas such as Iran, monitoring of the long-time effect of agronomic management on status of soil organic matter and soil physical indices is urgent.
کلیدواژهها [English]
- Physical characteristics
- Soil Quality indicators
- Residual Management
- Agronomy crop management
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