اثر عملیات زراعی بلند مدت بر تغییر شکل های اکسید آهن و کانی های خاک در ورتی سل های منطقه پیرانشهر

نوع مقاله : مقالات پژوهشی

نویسندگان

• سالار رضاپور ¹
• حنیفه آژاه ²

¹ ارومیه

² دانشگاه ارومیه

https://doi.org/10.22067/jsw.v31i3.57416

چکیده

تغییرپذیری و رفتار شکل‌های اکسید آهن و کانی‌های خاک در میزان توسعه و تکامل خاک اثرات قابل توجهی دارند و عملیات زراعی طولانی مدت می‌تواند این فرایند را تحت تاثیر قرار دهد. به منظور بررسی تاثیر عملیات زراعی طولانی مدت بر رفتار کانی‌های رسی و شکل‌های مختلف اکسید آهن، شش خاکرخ از خاک‌های ورتی ‌سل زراعی و غیر زراعی همجوار در منطقه پیرانشهر تشریح، نمونه برداری و تجزیه شدند. شکل‌های مختلف اکسید آهن شامل آهن پدوژنیک (Fed)، آهن کریستالی (Fecryst)، آهن کریستالی ضعیف (Feo) و آهن کمپلکس با مواد آلی (Fep) مورد مطالعه قرار گرفتند. همچنین مطالعات کانی شناسی خاک نیز به روش پراش اشعه ایکس (XRD) انجام شد. نتایج نشان داد که عملیات زراعی مستمر و طولانی مدت باعث تغییرات قابل توجهی در مقدار شکل‌های اکسید آهن نسبت به اراضی غیر زراعی همجوار شده است. بطوریکه مقدار آهن پدوژنیک در خاک‌های زراعی از 1 تا 64 درصد و آهن کریستالی نیز از 44 تا 90 درصد روند افزایشی نسبت به خاک‌های غیر زراعی نشان دادند که می‌تواند بیانگر تاثیر عملیات زراعی در تسریع فرایند هوادیدگی باشد. همچنین نتایج کانی‌شناسی نشان داد که عملیات زراعی تغییری در نوع (کیفیت) کانی‌ها ایجاد نکرده ولی در شدت و موقعیت پیک کانی‌ها بویژه در کانی‌های ایلایت، اسمکتایت و کلرایت، تغییرات قابل توجهی ایجاد شده است.

کلیدواژه‌ها

• آهن پدوژنیک
• آهن کریستالی
• خاک زراعی
• کانی شناسی

عنوان مقاله [English]

Effect of Long- term Agricultural Practices on Soil Iron Oxides Forms and Mineralogy in the Vertisols of the Piranshahr Region

نویسندگان [English]

• salar rezapour ¹
• H. Azhah ²

¹ Urmia university

² Urmia University

چکیده [English]

Introduction: Human activities such as intensive cultivation and land use changes alter nutrients fluxes (mainly iron) and mineralogy in soil and terrestrial ecosystems. Iron is an essential element for plants and microorganisms and its solubility is controlled by stable hydroxides, oxyhydroxides, and oxides. In general, parent material, climate, and landscape position are the major factors that accelerate the weathering of the minerals and rocks containing Fe in the regional scale. However, long-term cultivation and intensified agriculture may be the dominant attributes of modifications in soil properties like Fe compounds mainly in arid and semiarid regions, where the irrigational and agricultural practice is current over long-term periods. Although substantial data is documented on Vertisols properties, few studies are available to assess the effects of long-term continuous cultivation on the characteristic and distribution of iron oxides and their mineralogy, mainly in calcareous environments.
Materials and Methods: This study was conducted in the Piranshahr - Pasvah area (36° 46 to 36° 50 N and 45° 09 to 45° 50 E, 1500 m above sea level), West Azarbaijan Province, northwest of Iran. Six soil profiles belonging to three subgroups of Vertisols order (Chromic Calcixererts, Typic Haploxererts, and Typic Calcixererts) were described and sampled from the cultivated soils and similar soils from the nearby uncultivated region as grassland. Soil samples were air-dried and passed through a 2-mm mesh sieve before the analysis. Soil analysis included particle-size distribution, pH and electrical conductivity (EC), soil organic carbon (SOC), calcium carbonate equivalent (CCE), cation exchange capacity (CEC), the determination of iron oxides forms and mineralogical composition. Free or pedogenic Fe oxides (Fed) including crystalline, poorly crystalline, and organically bound Fe were extracted by dithionite–citrate–bicarbonate (DCB) method. Poorly crystalline and organically bound Fe (Feo) were extracted using 0.2 M ammonium oxalate (AO). Organic complex of Fe (Fep) was extracted by 0.1 M Na-pyrophosphate at pH 10. All Fe oxide forms were determined using atomic absorption spectrometry. The difference between DCB-Fe and AO-Fe was considered as an estimation of crystalline Fe oxides form.
Results and Discussion: The results showed that long-term cropping caused a considerable drop in organic carbon and calcium carbonates along with a noticeable rise in the values of clay and cation exchange capacity as a result of accelerated alteration by farming activities and interactions between the used irrigation water and soils receiving it. Long-term cultivation improved the amount of Fed and Fecry (crystalline Fe) from 1 to 64% and 44 to 90%, respectively, than those of uncultivated soils which can be explained in some pathways: (1) accelerated weathering of Fe-bearing minerals (such as biotite, chlorite, feldspars, amphibole, and pyroxene) in the cultivated soils and (2) the higher temperature condition and the more number of wetting–drying cycles in the cultivated soils compared to the uncultivated soils. Despite the fact that long-term cultivation caused a significant decrease in organic matter, a pronounced increase in organic complex of Fe with the range of 19 to 61% was recorded with farming practices. Such pattern can be contributed to the chemistry of organic matter and the presence of more stable fraction (passive fraction) of soil organic matter in the cultivated soils. The XRD patterns of primary Fe-bearing minerals (such as amphibole, pyroxene, and feldspar) had less intense in the cultivated soils compared to those of the adjacent uncultivated soils, indicating that probably cultivation promoted the instability and weatherability of Fe-bearing minerals as well as the loss of Fe from the minerals. In contrast, the X-ray reflections of secondary Fe-oxide minerals such goethite appeared to be higher, sharper and intense by long-term cropping, suggesting that agricultural practices also promoted the crystallization of the soil Fe oxides. Compared to the uncultivated soils, long-term agricultural practices caused some changes in X-ray reflections of chlorite, illite, and smectite.
Conclusions: The results showed that the weathering of Fe-bearing minerals and layer silicates, as well as the production of Fe oxide forms were promoted under long-term continuous cropping. Under cultivation, a pronounced increase in Fe-oxide forms, particularly Fed and Fecry, was recorded for the most of the examined soils which can be associated with the combined effects of increased soil temperature and moisture content from irrigation and farming practices. As emphasized, the combined effects of increased compounds from agricultural input (such as chemical and organic fertilizers, the compound of irrigation water, and moldboard tillage) as well as increased precipitation from irrigation interacted to create conditions for: (1) more intense the weathering of Fe-bearing minerals and (2) the more production of iron oxides forms in the cultivated soils.

کلیدواژه‌ها [English]

• Crystalline iron
• Cultivated soil
• Mineralogy
• Pedogenic iron

مراجع

1. Allen C.E. 2005. Physical and chemical characteristics of soil forming on Boulder Tops, Karkevagge, Sweden, Soil Science Society of American Journal, 69: 148-158.

2. Aniku J.R.F., and Singer M.J. 1990. Pedogenic iron oxide trends in a marine terrace chronosequence, Soil Science Society of American Journal, 54:147-142.

3. Bera R., Seal A., Banerjee M., and Dolui A.K. 2005. Nature and profile distribution of iron and aluminium in relation to pedogenic processes in some soils developed under tropical environment in India, Environmental Geology, 47:241-245.

4. Blume H.P., and Schwertmann U. 1969. Genetic evolution of profile distribution of aluminum, iron and manganese oxides, Soil Science Society of American Proceeding, 33:438-444.

5. Boettinger J.L., and Southard R.J. 1995. Phyllosilicate distribution and origin in Aridisols on a granitic pediment, Western Mojave Desert, Soil Science Society of American Journal, 59:1189-1198.

6. Bouyoucos G.J. 1962. Hydrometer method improved for making particle size analysis of soils, Agronomy Journal, 54:464-465.

7. Costantinia E.A.C., Lessovaiab S., and Vodyanitskiic Y. 2006. Using the analysis of iron and iron oxides in paleosols LTEM, geochemistry and iron forms for the assessment of present and past pedogenesis, Quaternary International, 156-157: 200-211.

8. Dalmolin R.S.D., Dick D.P., Klamt E., Couto E.G., and Rosa A.S. 2010. Mineralogical assemblage and iron oxides of soils of the Pantanal biome, Brazil. World Congress of Soil Science, Soil Solutions for a Changing World, Australia. Pp: 52-55.

9. Dolui A.K., and Bera R. 2001. Relation between forms of iron and aluminium and pedogenic processes in some Alfisols of Bihar and West Bengal, Crop Research, 25: 69-77.

10. Fiedler S., and Sommer M. 2004. Water and redox conditions in wetland soils-their influence on pedogenic oxides and morphology, Soil Science Society of American Journal, 68: 326-335.

11. Ghabru S.K., Arnaud S.T., and Mermut A.R. 1990. Association of DCB-extractable iron with minerals in coarse soil clay, Soil Science, 149:112-120.

12. Holmgren G.G. 1976. A rapid citrate-dithionate extractable iron procedure, Soil Science Society of American Proceeding, 31:210–211.

13. Igwe C.A., Zarei M., and Stahr K. 2010. Fe and Al oxides distribution in some Ultisols and Inceptisols of southeastern Nigeria in relation to soil total phosphorus, Environment Earth Science, 60:1103-1111.

14. Jahnson M.G., and Mcbride M.B. 1989. Mineralogical and chemical characteristics of Adirondack Spodosols evidence for para and noncrystallin aluminosilicate minerals, Soil Science Society of American Journal, 53:482-490.

15. Khormali F., and Abtahi A. 2003. Origin and distribution of clay minerals in calcareous arid and semiarid soils of Fars provinces, Southern Iran, Clay Minerals, 38:511-527.

16. Khormali F., and Abtahi A. 2003. Soil genesis and mineralogy of three selected regions of Fars, Bushehr and Khuzestan provinces of Iran, formed under highly calcareous conditions, Iran Agricultural Research, 20:67-82.

17. Khormali F., Abtahi A., and Owliaei H.R. 2005. Late Mesozoic Cenozoic clay mineral succession of southern of Iran and its paleo climatic implications, Clay minerals, 40: 191-203.

18. Khormali F., and Ajami M. 2011. Pedogenetic investigation of soil degradation on a deforested loess hillslope of Golestan Province, Northern Iran, Geoderma, 167-168:274–283.

19. Kittrick J.A., and Hope E.W. 1971. A procedure for particle size separation of soil for X-ray diffraction, Soil Science Society of American Journal, 35: 621-626.

20. Loveland P.J., and Digby P. 1984. The extraction of Fe and Al by 0.1 M pyrophosphate solutions: A comparison of some techniques, Soil Science, 35:243-250.

21. Maheney W.C., Hancock R.G.V., and Sanmugadas K. 1991. Extractable Fe-Al and geochemistry of late Pleistocene Paleosol in the Dalijia shan, Western China, Journal of Asian Earth Science, 6:75-82.

22. McKeague J.A., and Day J.H. 1966. Dithionite-and oxalate-extractable Fe and Al as aids in differentiating various classes of soils, Canadian Journal of Soil Science, 46:13–23.

23. Nelson R.E., and Sommers L.E. 1982. Total carbon. Organic carbon and organic matter. In A. L. Page et al. (ed) Methods of soil analysis. Part 2. 2nd. Agron. Monogr. 9. ASA and SSSA, Madison, WI, pp: 539-579.

24. Owliaie H.R., Heck R.H., and Abtahi A. 2005. The magnetic susceptibility of soil in Kohgilouye, Iran, Canadian Journal of Soil Science, 86:97-107.

25. Prasetyo B.H., and Gilkes R.J. 1994. Properties of iron oxides from red soils derived from volcanic tuff in West Java, Australian Journal of Soil Research, 32:781-794.

26. Rezapour S., Jafarzadeh A.A., Samadi A., and Oustan Sh. 2009. Impacts of clay mineralogy and physiographic units on the distribution of potassium forms in calcareous soils in Iran, Clay Minerals, 44:329–339.

27. Rezapour S., Jafarzadeh A.A., Samadi A., and Oustan Sh. 2010. Distribution of iron oxides forms on a transect of calcareous soils, north-west of Iran, Archive Agronomy and Soil Science, 56:165-182.

28. Rezapour S., and Samadi A. 2012. Assessment of Inceptisols soil quality following long-term cropping in a calcareous environment, Environmental Monitoring and Assessment, 184:1311–1323.

29. Schwertmann U., Taylor R.M. 1989. Iron oxides. In: J.B. Dixon, and Weed S.B. (eds) Minerals in soil environments. American Society of Agronomy, Madison, pp: 379–438.

30. Singh B., and Goulding, K.W.T. 1997. Changes with time in the potassium content and phyllosilicates in the soil of the Broadbalk continuous wheat experiment at Rothamsted, European Journal of Soil Science, 48: 651-659.