Assessing the Environmental Parameters of the Rice (Oryza sativa L.( in the Second Cropping and Ratoon Systems using Life Cycle Assessment (LCA)

Rice (Oryza sativa L.) is one of the most important food resources of more than half of the world's population. Rice, as the second most strategic crop, is the most important cereal after wheat. Excessive use of renewable and non-renewable resources in the agricultural sector, chemical control of rice diseases, and irreparable environmental damage of these systems potentially have a variety of environmental impacts on agricultural systems, such effects can be assessed by the life cycle assessment (LCA) approach. The purpose of the present research is to assess of knowing and comparing the trend of environmental pressure of the second and ratoon cropping systems of rice production in the paddy fields.

This research was conducted in 2020 in the paddy fields of Amol city with the focus on recognizing and comparing the trend of environmental pressure in rice production in the second and ratoon cropping systems. Accordingly, all data related to the second and ratoon rice cropping systems in different stages of rice production, from planting to harvesting phases, was collected in Amol region. In this study, to classify and quantify the environmental effects of rice production in two cropping systems using the LCA method are addressed. Furthermore, the environmental impacts of these systems such as global warming potential, eutrophication, and acidification of water and soil were also calculated. In this study, the functional unit of rice production systems were considered equivalent to one ton of paddy. Therefore, in order to evaluate the emission of greenhouse gases and energy in paddy fields, the required information was collected and interviewed by paddy farmers.

The findings of this study indicated that the highest global warming potential of rice was related to the rice second cropping system about 1896.92 kg carbon dioxide per ton of produced rice. Evaluation of the LCA in rice production process showed that in the group of environmental impact of global warming, about 1673.99 kg equivalent of carbon dioxide to the atmosphere has been released per ton of rice in ratoon cropping system. Direct emissions from on-farm activities in all two studied systems have played a major role in increasing global warming. The source of these pollutants is the combustion of diesel used in agricultural implements and machinery, accompanied by the emission of nitrogen dioxide, nitrogen oxides and other nitrogenous compounds resulting from the use of nitrogen fertilizers. Also, rice second cropping systems had a greater impact on the three categories of human health damage, ecosystem quality, and climate change than ratoon cropping systems. Moreover, the values of damages on the quality of the ecosystem in these systems were about 10089.08 and 7146.58 PDF*m2 * yr in the second and ratoon cropping systems, respectively. In addition, both rice production systems have shown the greatest impact on ecosystem quality and then on human health. Direct emissions from on-farm activities in the two studied systems have played a major role in increasing global warming. The source of these pollutants is the combustion of diesel used in agricultural implements and machinery, as well as the emission of nitrogen dioxide, nitrogen oxides and other nitrogenous compounds resulting from the use of nitrogen fertilizer.

The results revealed that the rice second cropping system had the higher amount of total emissions than the ratoon cropping system, therefore, rice ratoon production system is more environmentally friendly than the rice second cropping systems.
Acknowledgements
This research was funded by the Sari Agricultural Sciences and the Natural Resources University (SANRU) under contract No. d-110-99-16690. We would also like to thank the esteemed rice farmers in Amol region, Mazandaran province, Iran for their cooperation.