ارزیابی چرخه حیات در بوم‌نظام‌های تولید گندم (Triticum aestivum L.) ایران: 2- مقایسه مکانی در سطح کشور

نوع مقاله : علمی - پژوهشی

نویسندگان

1 فردوسی مشهد

2 دانشگاه فردوسی مشهد

چکیده

ارزیابی چرخه حیات (LCA) روش معتبر و دقیقی برای بررسی و مقایسه پیامدهای محیطی ناشی از فعالیت‌های انسان و از جمله روش‌های مختلف مدیریت در بوم‌نظام‌های زراعی می‌باشد که تعمیم نتایج آن به مقیاس ملی اطلاعات مفیدی را در مورد اثرات محیطی فعالیت‌های زراعی فراهم می-سازد. در این پژوهش نتایج اجرای LCA برای بوم‌نظام‌های کم، متوسط و پر نهاده تولید گندم کشور که قبلاً انجام شده بود جهت مقایسه اثرات محیطی بین 14 استان مورد استفاده قرار گرفت. به این منظور برای هر استان سطح زیر کشت گندم در سه نظام با سطوح مختلف مصرف نهاده تعیین شد و سپس بر اساس عملکرد هر نظام و سهم آن از سطح زیر کشت، پیامدهای محیطی هفت گروه تأثیر با استفاده از تغییر مقیاس خطی برای هر استان بر آوردشد. نتایج نشان داد که کارایی استفاده از زمین در استان‌های کشور بسیار متفاوت است. به‌طوری‌که استان خوزستان که 18 درصد از گندم کشور را تولید می‌کند دارای پایین‌ترین کارایی استفاده از زمین بود و در این استان برای تولید یک تن گندم به 4271 مترمربع زمین نیاز است، در حالی‌که این مقدار در استان تهران 2049 مترمربع می‌باشد. در واحد کارکردی هکتار، بیشترین پتانسیل گرمایش جهانی و سمیت اکولوژیکی مربوط به استان تهران بود که در آن نظام‌های پر‌نهاده بیشترین سهم را در سطح زیر کشت گندم دارند. در واحد کارکردی تن دانه، استان‌های همدان و خوزستان به‌ترتیب دارای کمترین و بیشترین پتانسیل گرمایش بودند. گروه‌بندی استان‌ها با روش تجزیه به مؤلفه‌های اصلی (PCA) نشان داد که تفاوت بین استان‌ها علاوه بر عملکرد گندم تابع توزیع نظام‌های کم، متوسط و پر‌نهاده در کل سطح زیر کشت استان‌ها نیز می‌باشد. مقایسه استان‌ها بر اساس نوعی شاخص نرمال شده محیطی که معیاری از مجموع هفت گروه تأثیر بود، نیز نتایج حاصل از PCA را تأیید کرد. بر اساس یافته‌های این تحقیق تولید یک تن گندم در استان همدان دارای کمترین اثرات محیطی در بین 14 استان تحت بررسی می‌باشد و در مقابل استان خوزستان برای تولید هر تن گندم بیشترین پیامدهای محیطی را به جا می گذارد. در بوم‌نظام‌های گندم کشور که با مصرف زیاد نهاده مدیریت می‌شوند، افزایش عملکرد به بالاتر از چهار تن در هکتار باعث افزایش شدید اثرات محیطی در هکتار شده، ولی عملکرد اضافی ناشی از مصرف نهاده‌ها به اندازه‌ای نیست که این اثرات را به ازای تن دانه گندم کاهش دهد. بنابراین، با وضعیت فعلی کارایی استفاده از نهاده‌ها در تولید گندم، افزایش عملکرد از طریق فشرده‌سازی (مصرف نهاده بیشتر) راه‌حل مطمئنی نبوده و پیامدهای محیطی جدی به‌همراه خواهد داشت.

کلیدواژه‌ها


عنوان مقاله [English]

Life Cycle Assessment (LCA) for Wheat Production Systems of Iran: 2- Spatial Comparison over the Country

نویسندگان [English]

  • Mahdi Nassiri Mahallati 1
  • Alireza koocheki 2
1 Ferdowsi University of Mashhad
2 Ferdowsi University of Mashhad
چکیده [English]

Introduction
Life cycle assessment (LCA) is a well-known and accurate method for comparison of environmental impacts of human activities including different agricultural management systems. Since agricultural activities are known as an important source of environmental pollution and greenhouse gas emission, LCA have been extensively applied for several tree and crop species around the country. However, these researches are generally conducted at field or district scales and due to variation in agronomic practices and input levels, the results cannot extended to regional or national level. In this paper using spatial upscaling method the results of LCA for wheat production systems with different level of inputs were extended to province and the results were subjected to statistical classification methods for comparison of impacts between provinces.
Materials and Methods
In this research the results of LCA for low, medium and high input wheat production systems of the country were upscaled to 14 provinces, details on LCA analysis of these systems is provided. For each province contribution of three management systems in cultivated area and wheat yield were extracted from official databases. Using these data the intensity of seven impact groups available from LCA were estimated for each province by linear upscaling method as described. Standardized values of seven impact categories over 14 provinces were subjected to principal component analysis (PCA) to compare provinces for overall impacts and separately for each impact category. In addition a normalized environmental index which integrates all impacts in a single index was calculated for direct comparison between provinces.
Results and Discussion
Results indicated that studied provinces had wide range of land use efficiency. Khozestan province with 18% of country wheat production had the lowest land use efficiency where 4271 m2 land is needed per ton wheat grain while it was the lowest (2079 m2) in Tehran. The highest per hectare global warming potential and ecotoxicity was obtained for Tehran province where contribution of high input systems in total cultivated area was at the maximum. However, per ton grain Hamadan and Khozestan provinces had respectively, the lowest and the highest global warming potential. Classification with principal component analysis (PCA) showed that difference between provinces in addition to yield, was highly related to the percentage distribution of low, medium and high input systems in total cultivated area. Comparison of provinces with a normalized environmental index showing the integrated effects of seven impact groups confirmed the results of PCA. Based on the results, taking into account all impact categories, production of one ton wheat grain in Hamadan had the lowest environmental impact between 14 provinces and Khozestan showed the highest impacts for production of the same amount of grain yield. In wheat production systems in Iran with high input management, increasing yield level above 4 t ha-1 may result to severe per hectare environmental impacts which cannot be compensated for by yield increment.

Conclusion
It is concluded that at current level of resource use efficiency in wheat production systems of the country, increasing wheat yield through intensification is not a reliable approach and will be led to strict environmental consequences.

کلیدواژه‌ها [English]

  • intensification
  • life cycle assessment
  • Normalized Environmental Index
  • Principal component analysis
  • Scaling
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