Economy

It is difficult to measure sustainable agriculture as a multidimensional concept. While it is relatively easy to express philosophical definitions of agriculture sustainability, providing an operational and methodology definition for evaluating the level of sustainability is difficult. Different methodological approaches have been formulated and developed to assess the sustainability levels of sustainable agriculture. However, there is no consensus on a comprehensive framework for identifying and selecting indicators, different scales of indicators, weighting and especially for aggregating individual indicators into a final composite indicator and rating of sustainability level. So, Evaluation of sustainable agriculture is an important challenge for agriculture researchers, agents, and policymakers. A comprehensive approach for stability analysis is the complexity of each other-need activities. That's why we need a comprehensive analytical framework for evaluating sustainable agriculture development and use. This study presents a certain methodological approach to evaluate and determine the sustainability of agricultural production at farm-scale which integrates all the individual indicators of ecological, economic and social stability into a comprehensive final index. In a case study, in order to test the proposed methodology, 22 individual indicators were selected. Then, a local condition of rice cultivation in Sari County was studied through an open review of 287 rice farmers.

Agricultural sustainability can be evaluated at different spatial scales including field, regional, national and even international measures. However, due to the specific conditions of each region, its natural environment, socio-economic conditions and agricultural techniques, necessity of a transparent scale is unavoidable. Most national indicators are not applicable at the scale of individual farms which are the purpose of the intended operations. In this study, 22 single index fields were selected to demonstrate and test the proposed methodology in a specific case study. Then, its relevance to the local conditions of rice cultivation in Sari County was studied by examining 287 rice farmers. Considering relative importance and impact of social, economic and ecological factors on the total sustainability, a methodology of Analytical Hierarchy Process (AHP) was applied by exploring the views of experts to determine the weight. Finally, the final composite indicator of sustainability was created through the integration of the three components of sustainability. A questionnaire was designed to collect data for the current farming operations. It consisted of three parts, namely: a) agricultural land management practices; b) economic performance and c) social characteristics of each farm. The questionnaire was designed in such a way to be completed in the shortest possible time. Thus, it was consisted of useful sections for measuring and providing information related to the entire system of agricultural production.

Discussion and conclusion
The results of this study indicate that 17.77% and 53.66% of rice production system is unstable and potentially unstable. While the sustainability level of social component was standing in a satisfactory situation, the sustainability level of economic and ecological components was still changing. In addition, farm sustainability was higher for those farmers using the method of biological control, low-product seed, agro-ecological management practices, owners of integrated land and participants in training and extension courses. The level of education, family labor, and the amount of self-consumption of rice are factors of positive and direct relations with ecological sustainability. On the other hand, the amount of rice production causes significant negative effects on it. Age, farming experience, level of education and the amount of self-consumption show a positive significant relation with social sustainability. In addition, education, land size, selfconsumption, the amount of produced rice and productivity index are in a significant positive relation with economic sustainability. In general, factors including education, extension communication, attending training courses and the information source of consumption play a key role in the increasing of farmers' awareness. In this study, to evaluate and compare the sustainability of agricultural production system in farm scale, a methodology framework has been provided by the combination of three components of sustainability, i.e. economic, social and environmental. However, it cannot be claimed that the proposed methodology is quite authentic to evaluate the complicated phenomenon of sustainability. Different facilitating assumptions are required for the use of this methodology. Of course, it has several advantages and also can be used for different purposes. Thus, the following hints are noteworthy in the methodology section:
- Variables and indicators of sustainability should be selected according to the specific circumstances and context of each area and the topic at hand, as well.
- Validation and preliminary test of indicators is ensuring their appropriateness and being measurable in the current conditions of any region.
- Weight allocation model based on the views of experts and AHP, can obviously show the importance of individual indicators in the final integrated one.
- The integration of the three components of sustainability into the final one should be due to the relative weight of the components.
- In the process of making indicators, positive and negative effects of indicators on the overall sustainability must be considered.

Introduction
Population growth, the need to provide food security, and pressure on natural resources in developing countries are facing a fundamental challenge for the sustainable production of food products. The need to pay attention to sustainability in agriculture has been confirmed at local, regional, national, and global levels. Sustainable agriculture is a system that uses resources efficiently, produces healthy food resources, preserves the quality of the environment and resources for future generations, and is economically dynamic. Sustainability is a qualitative concept that cannot be measured directly, so appropriate indicators should be selected to determine the amount and durability of an agricultural system. Efficiency is a significant factor in the productivity growth of production resources, especially in developing countries. Increasing efficiency can be considered a suitable and sustainable complement to a set of policies that encourage and protect domestic production and promote the optimal use of resources. The exact definition of efficiency can be found in Pareto's definition. According to the definition of efficiency, a system has Pareto efficiency so that it is impossible to improve the economic status of an individual from society without worsening the economic status of another individual. In other words, the reallocation of resources should not worsen the situation of some people in society. Therefore, improving the efficiency and optimal consumption of production factors in improving the sustainability of agricultural operations in the direction of sustainable development is inevitable. Based on this, the main goal of the present study is to determine the efficiency and optimal use of production resources by rice farmers in rural areas of Gotvand in the direction of sustainable development under conditions of uncertainty (the application of robust Data Envelopment Analysis (DEA)).

Methodology
Efficiency measurement methods are classified into two parametric and non-parametric methods according to their characteristics. The most apparent model proposed in the non-parametric framework is the DEA model. In DEA, the efficiency of a group of investigated units is determined by using a multiple set of input and output variables. One of the major limitations of the mentioned method is the high sensitivity of this method to the change in the value of input and output data, or in other words, the presence of uncertainty in these data. Because agriculture is always faced with uncertainty, when the input and output values ​​have uncertainty, the mentioned model faces problems. In this regard, it is necessary to use another method that can protect optimal solutions against uncertainty. Recently, various methods have been proposed to overcome the problem of uncertain data in DEA, such as Interval DEA (IDEA), Fuzzy DEA (FDEA) and Stochastic DEA (SDEA). Another method of dealing with uncertain data that was introduced in mathematical programming models in the late 1990s is Robust DEA (RDEA). This method does not have some shortcomings in other methods for applying uncertainty conditions in the DEA model. The RDEA is one of the robust and valuable models in conditions of uncertainty, and in this study, this method was used to analyze the efficiency of rice farmers. The required data in the study area was obtained through the distribution and completion of the questionnaire in 2018 by 121 rice farmers considering the statistical population and using simple random sampling.

Discussion and conclusion
The average technical efficiency in the state of constant return to scale efficiency and at the level of 0.5 deviation probability and 20% uncertainty level is equal to 0.79, which means that rice farmers can use a fixed technology without reducing production, reduce their input consumption by 21% and reach the production efficiency bound. As a result, the producers of the studied area need to use production inputs optimally to produce a given level of production. However, the actual values ​​of input consumption by rice farmers in rural areas are far from the estimated optimal values. In other words, there is excess consumption for all inputs. The most inefficient inputs in the present study are the area under cultivation and herbicide. Therefore, achieving the optimal level of consumption of these inputs without reducing production by reducing 48% and 45% in the consumption of the cultivated area and herbicide, respectively. Considering the low technical efficiency and unfavorable input consumption among the rice farmers in the researched rural areas, it is suggested to identify efficient units and serve as a reference for inefficient units and develop a regular annual plan for optimal input consumption by farmers and as a result of improving efficiency, to improve the sustainability of agricultural operations in line with the goals of sustainable development. Also, educational planning is recommended to use suitable and advanced technologies to increase the productivity of production factors.