عنوان مقاله [English]
Introduction Rice, as the second most strategic crop, is the most important cereal after wheat. In Iran, rice is so essential that people consume it as part of their main meal at least once a day. Due to the increase in consumption inputs in conventional paddy systems, chemical control of rice diseases and consequently increase in consumption costs, irreparable environmental damage of these systems, always adds to the need to pay attention to alternative systems. Prediction of agricultural energy output and environmental impacts play the most important role in conservation of environment as well as energy management. A wide range of methods tapping into environmental performances related to agricultural activities have been proposed, among which the known life cycle assessment (LCA) method is deemed mostly employed. As a standard method which aims for holistic evaluation of the environmental resources and impact, LCA measures the process of a product's entire life cycle, or in other words, the analysis of the possible environmental impacts any product bears during their life would be assessed by LCA.
Materials and Methods This research was conducted in rice fields located in Mazandaran province in Babol, Fereydounkenar, and Amol counties as the main rice paddy center of Mazandaran province, in 2019 cropping season. Each of the systems was examined in terms of energy components and environmental impacts. In this study, to classify and quantify the environmental effects of rice production in various cropping systems using LCA method and also the energy components and energy efficiency in these systems are addressed. Therefore, in order to evaluate the emission of greenhouse gases and energy in paddy fields, the required information was randomly collected some farms through direct interviews with the rice growers of Mazandaran. In this regard, the sample size is calculated by using Cochran's formula.
Results and Discussion The findings of this study showed that the maximum amount of input energy equal to 60225.42 MJ / ha in conventional systems and the minimum values of 18662.14 MJ / ha were allocated to the organic system. Diesel fuel input energy had the largest share of total input energy. The highest energy efficiency of 0.17 kg per MJ and energy ratio of 2.57 was allocated to the organic system. Also, the evaluation of life cycle in rice production showed that in the global warming group of environmental impact by CML2 baseline method, for each ton of paddy produced in conventional, low-input and organic systems, respectively, about 2408.90, / 85.90, respectively. 1777 and 7993/1193 kg of carbon dioxide equivalent to the atmosphere are released. Direct emissions from On-Farm activities in all three 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.
Conclusion According to the results of this research work, from the environmental perspective, organic system has highly the best potential of being recommended following by low external input system in order to reach environmentally friendly agriculture as sustainable cultural operations in comparison with conventional cultivation practices. Farther, the results showed that the conventional system had the highest amount of total emissions and then the low input system is in the next position. Obviously, the organic system is the most environmentally friendly system and the conventional system has the highest amount of emissions. In order to give a broader evaluation of the organic and some low input systems, studies on such issues should be highly continued.
Acknowledgements Thanks and appreciation from the financial support provided by the Department of Agronomy and Plant Breeding Engineering, Sari Agricultural Sciences and the Natural Resources University of Sari, Iran.