ارزیابی توانایی بالقوه ترسیب کربن اندام های هوایی و زیرزمینی و پتانسیل گرمایش جهانی گندم (triticum aestivum l.) در استان خراسان رضوی

به‌منظور تعیین خصوصیات خاک و توانایی بالقوه ترسیب کربن اندام های هوایی و زیرزمینی گندم (triticum aestivum l.)، نمونه برداری به‌روش تصادفی سیستماتیک از پنج نقطه در 25 مزرعه در استان خراسان رضوی در سال های 1395 و 1396 در قالب طرح کاملاً تصادفی با سه تکرار انجام شد. برای تعیین ضرایب تبدیل ترسیب کربن در اندام های هوایی و زیرزمینی شامل سنبله، ساقه، برگ و ریشه از روش احتراق استفاده شد. میزان انتشار گازهای گلخانه‏ای شامل 2co، o2n و 4ch با استفاده از ضرایب انتشار محاسبه شد. نتایج نشان داد که میانگین محتوی کربن آلی، نیتروژن کل، فسفر قابل دسترس، پتاسیم قابل دسترس، وزن مخصوص ظاهری، اسیدیته و هدایت الکتریکی خاک مزارع گندم به‌ترتیب 0.98 درصد، 0.022 درصد، 27.07 پی پی ام، 341.32 پی پی ام، 1.37 گرم بر سانتی متر مکعب، 7.81 و 1.42 دسی زیمنس بر متر تعیین شد. بالاترین و پایین ترین ضریب تبدیل به‌ترتیب برای سنبله + دانه (52.0 درصد) و ریشه (31.99 درصد) به‌دست آمد. مجموع توان بالقوه ترسیب کربن اندام های هوایی و زیرزمینی برابر با 8.25 تن در هکتار تعیین گردید که بیشترین و کمترین میزان به‌ترتیب برای ساقه و ریشه با 4.28 و 0.35 تن در هکتار حاصل گردید. مجموع پتانسیل گرمایش جهانی گندم به‌ازای نهاده های مصرفی و عملیات زراعی 8884.86 کیلوگرم معادل 2co به‌ازای یک تن دانه محاسبه گردید که بیشترین میزان با 8092.24 کیلوگرم معادل 2co به‌ازای یک تن دانه به سوخت های فسیلی اختصاص داشت.

Evaluation of Carbon Sequestration for Above-Ground and Below-Ground Tissues and Global Warming Potential of Wheat (Triticum aestivum L.)

IntroductionCO2 is considered the most important greenhouse gas, due to the dependence of world economies on fossil fuels. CO2 concentration are enhancing in the last decades, mainly due to the increase of anthropogenic emissions. Carbon dioxide capture is a technology aimed at mitigating greenhouse gas emissions from burning fossil fuels during industrial processes. Conservation tillage, crop rotation, and crop residue management are agronomic practices that potentially decrease CO2 and other greenhouse gas emissions from agriculture. Crop residues also improve organic matter decomposition due to declined soilresidue contact. Soil is one of the significant “friends” in combating climate change and global warming, and a zerosoil consumption approach is the best way to stop adverse effects, although it is not the only one that should be applied. The soil has been considered as a possible carbon sink for sequestering atmospheric CO2.Our purposes were to determine a set of coefficients for calculating conversion coefficients, dry weight, organic carbon, and carbon sequestration of aboveground and belowground tissues and assess global warming potential (GWP) for wheat as an essential crop in Khorasane Razavi province. Materials and MethodsA systematic random sampling method was employed to select five samples from 25 fields situated in KhorasanRazavi Province, Iran, during 2016 and 2017. The experimental design was a completely randomized design with three replications. Belowground tissues by using a cylinder were manually sampled and then separated from the soil. After sampling, the aboveground tissues (such as flower and leaf) were isolated from belowground tissues (including tunic and corm) to measure the aboveground and belowground biomasses, respectively. Aboveground and belowground biomasses were separately dried to constant weight and expressed on a dry matter basis. Conversion coefficients of above ground and below ground tissues were determined with the combustion method separately. Then, sequestration carbon potential for above ground and below ground tissues of saffron and soil were computed. The ash method was used to determine the conversion coefficients in spikes, stems, leaves, and roots. Finally, greenhouse gases (such as CO2, N2O, and CH4) emission were also calculated using emission coefficients. Cronbach apos;s alpha was used for assessing the reliability of the questionnaire.For statistical analysis, analysis of variance and Duncan’s test were performed using SAS version 9.3. Results and DiscussionThe results showed that dry weight, organic carbon content, conversion coefficients, and carbon sequestration for above ground and below ground tissues of wheat were significantly different. The biomass of aboveground tissues was higher than belowground tissues of wheat. The results revealed that the maximum (52.0%) and minimum (31.99%) conversion coefficients of wheat were related to spikes (seeds included) and roots, respectively. Besides, the total carbon sequestration of belowground and aboveground of wheat was calculated 8.25 t.ha1 so that the maximum (4.28 t.ha1) and minimum (0.35 t.ha1) values were found in stems and roots, respectively. GWP was recorded as 8884.86 kg CO2equiv. per one ton of seed. ConclusionThis study shows that while there is significant potential for sequestering carbon in wheat agroecosystems through root and straw incorporations. It is recommended that returning wheat crop residues to the soil affected the soil apos;s physical, chemical, and biological properties. Furthermore, as nitrogenous fertilizer application plays a crucial role in increasing GWP, thus it is suggested that organic fertilizers and legumes might be suitable alternatives for chemical fertilizers. It is therefore concluded that the application of crop residues in agroecosystems seems to be a rational ecological approach for sustainable management of wheat agroecosystems with a consequence of the reduction in greenhouse gases and mitigation of climate change. This could make a significant contribution to improving agricultural sustainability and stability in arid and semiarid regions.