Evaluating the potential of carbon sequestration and global warming potential for saffron fields (Case study: Khorasan-e Razavi Province)

IntroductionIncreases in the concentration of CO2 in the atmosphere have prompted renewed interest in enhancing the soil pools of carbon in the agroecosystems to mitigate climate change and global warming and also improve quality of soil. The soil organic carbon (SOC) pool represents a dynamic equilibrium of gains and losses of carbon. Conversion of natural ecosystems to agroecosystems causes depletion of the SOC pools. The depletion is intensified when the output of carbon exceeds the input and when soil degradation is intensity. Terrestrial ecosystems contributed to atmospheric CO2 enrichment.
Carbon sequestration implies transferring atmospheric CO2 into long-lived pools and storing it securely so it is not immediately loosed. Thus, soil carbon sequestration means improving SOC and soil inorganic carbon pools through land use and recommended management practices.
Our purposes were to determine a set of coefficients for calculating conversion coefficients, dry weight, organic carbon and carbon sequestration of above-ground and below-ground tissues for saffron in Khorasan-e Razavi province.
Materials and Methods A survey experiment was conducted based on a completely randomized design during 2016. Sampling was performed with random-systematic method from 10 fields by using 30 plots of 0.5 m2 and along three transects of 50 m. Below-ground tissues by using cylinder were manually sampled and then separated from the soil. After sampling, the above-ground tissues (such as flower and leaf) were separated from below-ground tissues (including tunic and corm) as to measure the above-ground and below-ground biomasses, respectively. Above-ground and below-ground 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 combustion method separately. Then, sequestration carbon potential for above- ground and below- ground tissues of saffron and soil were computed.
Final, after the calculation of emission for greenhouse gases including CO2, N2O and CH4 based on emission indices, global warming potential (GPW) were calculated.
For statistical analysis, analysis of variance and least significant difference (LSD) were performed using SAS version 9.3.
Results The results showed that dry weights, organic carbon contents, conversion coefficients and carbon sequestration for above- ground and below- ground tissues of saffron were significantly different. Biomass of below- ground tissues were higher than above- ground tissues. The highest and lowest carbon sequestration for above- ground and below- ground tissues were calculated for corm and flower with 5.83 and 0.14 t.ha-1, respectively. The highest emission of greenhouse gas was belonged to fossil fuels with 39.78 kg. Equiv. CO2 and GWP was computed 7.21 t Equiv. CO2 per one ha.
ConclusionIt is therefore concluded that organic management and use of crop residues, cow manure and organic fertilizers seems to be a rational ecological approach for sustainable management of saffron agroecosystem with a consequence of reduction in greenhouse gases and mitigation of climate change.