@article { author = {Boroumand Rezazadeh, Elaheh and Koocheki, Alireza and Rezvani Moghaddam, Parviz and Nasiri Mahalati, Mahdi and Lakzian, Amir}, title = {Estimation of Carbon Sequestration in Iran Agroecosystems using Empirical Models}, journal = {Journal Of Agroecology}, volume = {11}, number = {1}, pages = {103-122}, year = {2019}, publisher = {Ferdowsi University of Mashhad}, issn = {2008-7713}, eissn = {2423-4281}, doi = {10.22067/jag.v11i1.50344}, abstract = {Introduction: Carbon sequestration is defined as the permanent gain of carbon by soil, plant or water. Soil as the largest terrestrial carbon pool plays an important role in the global carbon cycle. Due to the role of agricultural systems in CO2 emission, attention to the carbon cycle in agricultural systems is of prime importance. So, the interest in agricultural soils and plant biomass as a carbon sink and an operational mechanism for reducing the atmospheric CO2 level, is increasing. It is estimated that world’s crop-based agriculture occupies 1.7 billion hectares, which can store up to 170 Pg carbon. Thus, the aims of this study were to simulate the relationship between crop residue decomposition rate with carbon to nitrogen ration (C:N) (an index of residue quality) as well as soil moisture regimes (the most important factors in residue decomposition) and also estimation of the attainable carbon sequestration in irrigated systems of five major crops in Iran based on the simulated model. Materials and methods: Residue decomposition rate of wheat, maize, rapeseed, cotton and soybean (with C:N ratios of 131, 69.7, 87.1, 57.8 and 95.9 , respectively)  in different soil moisture regimes (100, 60 and 30 percentage of field capacity) was studied in a 390-day incubation experiment. Study data was used for simulation of residue decomposition and relative decomposition rate was defined as a function of moisture (fm), C:N (fC:N) and temperature (ftemp). The simulated model was used to evaluate attainable carbon sequestration of the studied crops in five years from 2002-2003 to 2006-2007 based on yield, harvest index and shoot to root ratio in three scenarios of residue retention (100, 50 and 0 percentage of total residue produced) as well as three scenarios of soil moisture regimes of 100, 60 and 30 percentage of field capacity for different provinces of Iran. In this step, residue decomposition during one year after harvest was calculated using fm, fC:N and ft. The difference between proportions of the residue returned to the soil and decomposed residues were considered as un-decomposed residue which was multiplied by 0.45 to gain attainable carbon sequestration. Data of attainable carbon sequestration was analyzed as factorial experiment based on completely randomized design. Results and discussion: Results indicated that higher C:N and therefore lower residue quality caused lower residue decomposition rate. This parameter was also decreased in soils with lower moisture. Effects of soil moisture on reside decomposition was more pronounced than residue quality. comparison of attainable carbon sequestration in Iran’s provinces revealed that in wheat cropping systems: Kermanshah and Sistan and Balouchestan, in maize: Qazvin and Southern Khorasan, in rapeseed: Isfahan and Boushehr, in cotton: Eastern Azarbaijan and Hormozgan and in soybean cropping system: Ardebil and Eastern Azarbaijan provinces had the highest and lowest attainable carbon sequestration, respectively. Attainable carbon sequestration in all crops was decreased with increasing soil moisture from 30 to 60 and 100% of FC and decreasing residue retention from 100 to 50 and 0 % of total crop residue production. Maize and soybean showed the highest and lowest capability of carbon sequestration, respectively. Conclusion Results of the present study highlight the effects of environmental factors such as soil moisture as well as inherent properties of plant residues on residue decomposition. Climate and residue quality are the main determining factors of soil microorganisms activity and residue decomposition and therefore soil attainable carbon sequestration. Better soil moisture condition and temperature, also higher residue quality increases microorganisms activity resulting in more residue decomposition. Furthermore, plant biomass and residue management affects attainable carbon sequestration. Resultant of the mentioned factors determines attainable carbon sequestration in soils of agroecosystems. Regarding to the total carbon sequestration of afore-mentioned crops, Ardebil and Sistan and Balouchestan provinces showed the highest and lowest carbon sequestration, respectively.}, keywords = {Air Temperature,residue decomposition,residue retention,Soil Moisture}, title_fa = {برآورد میزان ترسیب کربن در بوم‌نظام‌های زراعی ایران با استفاده از مدل‌های تجربی}, abstract_fa = {ترسیب کربن به معنای افزایش دائمی ذخیره کربن در خاک، ماده گیاهی یا آب بوده و خاک به عنوان بزرگ‌ترین مخزن کربن در بوم‌نظام­های خشکی دنیا، نقش مهمی در چرخه جهانی کربن دارد. هدف این مطالعه، مدل­سازی رابطه سرعت تجزیه بقایای گیاهان زراعی با رژیم‌های رطوبتی خاک و نسبت کربن به نیتروژن بقایا و نیز محاسبه میزان کربن قابل ترسیب در کشت آبی پنج محصول زراعی عمده در ایران بود. به همین منظور تجزیه بقایای گیاهی گندم (Triticum aestivum L.)، ذرت (Zea mays L.)، کلزا (Brassica napus L.)، پنبه (Gossypium herbaceum L.)، سویا (Glycine max L.) در رژیم‌های مختلف رطوبتی خاک طی 390 روز انکوباسیون مورد مطالعه قرار گرفت و از داده‌های حاصله برای مدل­سازی تجزیه بقایا استفاده گردید. همچنین محاسبه میزان کربن قابل ترسیب در این محصولات در پنج سال زراعی بر اساس عملکرد، شاخص برداشت و نسبت اندام‌های هوایی به ریشه در سه سناریوی بازگشت کامل بقایا، بازگشت 50 درصد بقایا و حذف کامل بقایای اندام‌های هوایی و سه سناریوی رطوبتی 100، 60 و 30 درصد ظرفیت مزرعه انجام شد. مقایسه میزان کربن قابل ترسیب در استان‌های مختلف نشان داد که در کشت گندم: استان‌های کرمانشاه و سیستان و بلوچستان، ذرت: قزوین و خراسان جنوبی، کلزا: اصفهان و بوشهر، پنبه: آذربایجان شرقی و هرمزگان، سویا: اردبیل و آذربایجان شرقی به ترتیب بیشترین و کمترین مقدار کربن قابل ترسیب را دارا بودند. با افزایش میزان رطوبت از 30 به 60 و 100 درصد ظرفیت مزرعه و همچنین با کاهش درصد برگشت بقایا به خاک از 100 به 50 درصد و حذف کامل بقایا، میزان کربن قابل ترسیب در خاک همه محصولات مورد مطالعه کاهش یافت. در بین محصولات مورد مطالعه، ذرت و سویا به ترتیب از بالاترین و پایین‌ترین میزان کربن قابل ترسیب برخوردار بودند. همچنین، در بین استان‌های مختلف از نظر مجموع کربن قابل ترسیب محصولات مورد مطالعه، استان‌ اردبیل بیشترین و استان‌ سیستان و بلوچستان کمترین مقدار کربن قابل ترسیب در خاک را دارا بودند.}, keywords_fa = {درصد تجزیه,رطوبت خاک,بازگشت بقایا}, url = {https://agry.um.ac.ir/article_36839.html}, eprint = {https://agry.um.ac.ir/article_36839_7ccb508c562aff13d3a5fd3d8205211a.pdf} }