تاثیر عوامل زراعی و خصوصیات خاک بر تنوع و ترکیب جامعه علف‌هرز مزارع گندم (Triticum aestivum L.) در شهرستان جاجرم

نوع مقاله : علمی - پژوهشی

نویسندگان

چکیده

این مطالعه با هدف ارزیابی تأثیر عوامل محیطی بر تنوع و ترکیب جامعه علف هرز گندم (Triticum aestivum L.) شهرستان جاجرم در سال 1388 انجام گرفت. برای این منظور اطلاعات زراعی (مصرف علف‌کش‌، مقدار نیتروژن مصرفی و نوع محصول قبلی) و خصوصیات خاک (pH، بافت و مقدار فسفر خاک) 16 مزرعه گندم در این شهرستان جمع آوری شد. شاخص تنوع شانون، غنای گونه‌ای و شاخص غالبیت سیمپسون به عنوان اجزای تنوع محاسبه شدند. مقایسه میانگین‌ها نشان داد که مصرف علف‌کش در مقابل عدم مصرف آن، بافت سیلتی در قیاس با بافت لومی و کشت گندم متعاقب یک‌سال آیش نسبت به کشت آن بعد از خربزه سبب کاهش معنی دار غنای گونه‌ای (92/4 در مقابل 12/7 ، 5 در مقابل 5/6 و 12/5 در مقابل 75/6 به ترتیب برای علف‌کش، بافت خاک و محصول قبلی) و شاخص شانون (08/1 در مقابل 6/1 ،1/1 در مقابل 48/1 و 19/1 در مقابل 49/1 به ترتیب برای علف‌کش، بافت خاک و محصول قبلی)، ولی افزایش شاخص سیمپسون (43/0 در مقابل 25/0 ،41/0 در مقابل 3/0 و 39/0 در مقابل 29/0 به ترتیب برای علف‌کش، بافت خاک و محصول قبلی ) گردید. به‌کارگیری آنالیز رگرسیون حاکی از وجود رابطه خطی معکوس بین مقدار نیتروژن مصرفی با غنای گونه‌ای و شاخص شانون (45/0=2r) بود. بین مقدار نیتروژن مصرفی و شاخص غالبیت سیمپسون رابطه خطی مثبت حاصل گردید (46/0=2r). غنای گونه‌ای، شاخص شانون و شاخص سیمپسون به pH و مقدار فسفر خاک وابستگی معنی‌داری نشان ندادند. استفاده از آنالیز افزونگی منجر به ظاهر شدن الگوهایی در ترکیب جامعه گیاهی در پاسخ به عوامل محیطی گردید (001/0=p-value،03/4=F). مصرف علف‌کش به‌عنوان عامل اصلی ایجاد تغییرات در ترکیب گونه‌ای شناخته شد. در مزارع گندم با سابقه مصرف علف‌کش توفوردی و استفاده زیاد از کودهای نتیروژن کشیده برگ‌ها جامعه گیاهی غالب را تشکیل دادند. روش تقسیم بندی واریانس نشان داد عوامل زراعی در مقایسه با عوامل خاکی سهم بیشتری در تشریح تغییرات در ترکیب جامعه علف هرز دارا می‌باشند.

کلیدواژه‌ها


عنوان مقاله [English]

Effects of crop factors and soil characteristics on weed composition and diversity in wheat (Triticum aestivum L.) fields in city of Jajarm

نویسندگان [English]

  • G.A. Rassam
  • N. Latifi
  • A. Soltani
  • B. Kamkar
چکیده [English]

The study was performed for assess the environmental factors affecting weed species diversity and composition of wheat (Triticum aestivum L.) fields in Jajarm, North-Khorasan of Iran, in 2009. The crop management (herbicide, amount of nitrogen applied and preceding crop type) and edaphic factors (pH, texture and content of phosphorus) of 16 fields were collected. Shannon’s diversity index, species richness and Simpson’s dominance index were used as measures of species diversity. Means comparison showed that use of herbicide versus non-herbicide application, silt texture than loam texture and planting after fallow versus planting after melon significantly decreased species richness (4.92 versus 7.12, 5 versus 6.5 and 5.12 versus 6.75 for herbicide, soil texture and preceding crop type, respectively) and Shannon’s diversity index (1.08 versus 1.6, 1.1 versus 1.48 and 1.19 versus 1.49 for herbicide, soil texture and preceding crop type, respectively), but increased Simpson’s dominance index (0.43 versus 0.25, 0.41 versus 0.3 and 0.39 versus 0.29 for herbicide, soil texture and preceding crop type, respectively). Regression analysis revealed negative linear relationship between applied nitrogen and diversity components (r2= 0.45). The relationship between applied nitrogen and Simpson’s dominance index was positively linear (r2= 0.46). There wasn’t relationship between pH and phosphorus of soil with Shannon’s diversity index, species richness and Simpson’s dominance index. Redundancy analysis (RDA) resulted in patterns per weed community composition (F= 4.03, P-value= 0.001). Major changes in weed species composition in the study area were associated with application of herbicide. Using of 2, 4- D and nitrogen fertilizers lead to domination of grass in these fields. The method of variation partitioning out showed that crop factors on changes in arable weed species composition are more important edaphic variables.

کلیدواژه‌ها [English]

  • Herbicide
  • Nitrogen
  • Shannon’s diversity index
  • Species richness
  • Redundancy analysis
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