تاثیر روش‌های مدیریتی بر خصوصیات بیولوژیکی خاک در بوم‌نظام‌های کشاورزی استان اصفهان

این تحقیق به‌‌منظور بررسی تاثیر روش‌‌های مدیریتی بر جمعیت کرم‌های خاکی، ذی توده و تنفس میکروبی خاک در بوم نظام های کشاورزی در سال زراعی 91-1390 در سطح مزارع شهرستان‌های استان اصفهان انجام گرفت. ابتدا در هر یک از 23 شهرستان استان اصفهان، شش مزرعه انتخاب و به‌منظور گروه‌بندی مزارع مورد مطالعه، پرسشنامه‌ای تنظیم و از طریق مراجعه به زارعین تکمیل گردید. سپس بر اساس اطلاعات پرسشنامه‌ها، مزارع به سه گروه (مزارع کم‌نهاده، متوسط نهاده و پرنهاده) طبقه‌بندی شد. در هر شهرستان دو مزرعه از هر گروه نهاده انتخاب و مورد بررسی قرارگرفت. نتایج نشان داد که جمعیت کرم‌های خاکی، ذی توده و تنفس میکروبی خاک مزارع مورد مطالعه تحت تاثیر روش‌های مدیریت زراعی، روش‌های خاک‌ورزی و کاربرد میزان و نوع نهاده های مصرفی قرار گرفت. خاک مزارع کم‌نهاده دارای بالاترین مقدار تنفس (30.5 میلی‌گرم دی اکسیدکربن در کیلوگرم خاک) و بیشترین ذی توده میکروبی (380 میکروگرم در کیلوگرم خاک) و بیشترین جمعیت کرم خاکی (سه عدد در هر کیلوگرم خاک) در نظام‌های زراعی کم ‌نهاده بود. درحالی‌که مقدار تنفس، ذی توده میکروبی و تعداد کرم خاکی در نظام‌های زراعی پر نهاده کمترین مقدار (به‌ترتیب 18.5 میلی‌گرم دی اکسیدکربن، 195 میکروگرم و صفر در هر کیلوگرم خاک) بود.

The Effects of Management Practices on Soil Biological Properties of Esfahan Agroecosystems

IntroductionIn general, management methods applied at the agroecosystems, can affect the population and activity of micro and macro organisms. In high input farms, which use especially large amounts of chemical inputs, it has destructive effects on soil agroecosystems and soil organisms. Soil is an essential component of agricultural systems and the key to soil fertility is to preserve the biodiversity of the soil ecosystem. Microorganisms are the main factor in advancing ecological processes in ecosystems, and soil microbial processes affect the functioning of ecosystems such as nutrient rotation, soil fertility, global carbon change, and soil organic matter recirculation. Organic matter is part of soil that is produced by soil organisms and contains plant and animal remains in different stages of decompositation. This research was conducted in order to evaluate the effects of management practices on earthworms population, microbial respiration and biomass of soils of Esfahan fields an experiment was conducted during 20112012. Materials and MethodsIn each of 23 county of Esfahan, 6 fields were selected and in order to fields classification, evaluation was conducted using questionnaires and that farmers filled. Within questionnaires, field classification was into three groups (low inputs, medium inputs and high inputs). In the laboratory, each soil sample from the studied farms was examined separately and the number of earthworms in each sample was counted and recorded. In order to evaluate the population and microbial activity, soil carbon and nitrogen were measured by microbial extraction method. Soil samples were extracted in the laboratory and the organic carbon of the extracts was measured using a TOC device and the microbial carbon was calculated. Results and DiscussionsResult indicated that soil of low inputs had the highest microbial respiration (30.5 mgCO2.kg1 soil), biomass (380µg.kg1 soil) and earthworms population (3 Per kg Soil). Soil of high inputs had the lowest microbial respiration, biomass and earthworms population (18.5 mg CO2 .kg1 soil, 195µg.kg1 soil and 0 per kg Soil respectively). ConclusionAccording to other studies, in soils where there are plant residues or green manure and cover crops have been used, a high level of earthworm population, biological activity and soil fertility can be maintained. Earthworm populations are effected by structure and soil fertility. Microbial population in low inputs agroecosystems, was higher than medium and high inputs agroecosystems. Thus microbial respiration was higher in low inputs agroecosystems. Earthworms population in low inputs agroecosystems was also higher than medium and high inputs agroecosystems and the reason of high earthworms population was more residual plants in low inputs agroecosystems. Microbial biomass in low inputs agroecosystems higher than medium and high inputs agroecosystems. Reason of microbial biomass decrease in high inputs agroecosystems was application of conventional tillage. According to other studies, crop rotation and soil improvement has important roles in promoting population and soil microbial activity. The results of this study showed that the application of low inputs management methods leads to improved population and activity of soil microbial communities, so replacing chemical inputs with field inputs as a way to promote soil microbial communities. According to other researchers, less soil degradation in low input agroecosystems due to the use of notillage or minimum tillage methods leads to improved soil microbial population. The results of similar research indicates that the use of reduced plowing methods strengthens the population of earthworms. On the other hand, the use of pesticides and herbicides as well as the burning of plant debris on the soil surface reduces the population of earthworm. In soils were mulch is used, temperature fluctuations were reduced, which preserves earthworms in the soil. Acknowledgements:I would like to express my sincere appreciation to all the people who helped me during this research and provided me with the necessary facilities. I would also like to thank the professors and staff of the faculty of agriculture of Ferdowsi University of Mashhad for their cooperation with me.