بررسی سلامت بوم‌نظام‌های زراعی در استان‌های شرقی ایران

Introduction
The conventional agricultural ecosystems (agroecosystems) are the complex systems which in order to produce the higher amount of food, fiber, feed and fuel have been significantly manipulated. Rapid growth of world population and demand for agricultural products resulted in higher pressure on agroecosystems. In recent decades achieving to maximum production was the main goal of conventional agriculture. In order to increase yield on production usually these agroecosystems need to external inputs such as chemical fertilizers and pesticides which have the negative effects on human health and also environment.  Sustainable and healthy agroecosystems are based on profitable farms that use fewer external inputs, integrate animal and plant production where appropriate, maintain a higher biotic diversity, emphasize eco friendly technologies that are appropriate to the scale of production, and efficiently use the renewable forms of energy. For example diversifying the farm with several crops or using appropriate rotation helps to reduce the risk of biotic and abiotic stresses. The complex nature of agroecosystem implies that any evaluation of agroecosystem health must consider the dynamics of multiple components. The current paper presents an applied method to evaluate agroecosystem health using a number of main indicators.
 Materials and Methods
In order to study the agroecosystem health in four eastern provinces of Iran (i.e. Sistan and Baluchestan, South khorasan, Razavi Khorasan and North Khorasan) during 2002-2011 the current survey was conducted. The required data and information obtained from statistical database and also questionnaires. For each year the total value of agroecosystem health calculated using 29 different indexes. Different indexes calculated based on their scientific definitions. For example property distribution index calculated by dividing the total area of agricultural lands on number of farmer in each city. Because of different nature of selected indexes and also wide range of them, in order to facilitate comparison all of the calculated indexes normalized using the equation (1), in this equation Xnorm is the normalized value of each index, Xmax and Xmin are the highest and lowest value of X, respectively.
Equation (1):
 
Results and Discussion
Based on results the highest value of structural health was calculated for Sistan and Baluchestan province and the lowest value was for Razavi KhorasanIt seems that in Sistan and Baluchestan the higher values for some of the indexes such as area under cultivation of forage and perennial crops, appropriate use of agricultural machinery and also plant diversity improved the structural health. The similar results also observed for organizational health. Lower use of pesticides and chemical fertilizers are the main reason for better conditions of organizational health in Sistan and Baluchestan province. The result for functional health was different and the best condition of functional health observed in Razavi Khorasan whereas the worst condition observed in South Khorasan. The higher value of functional health of agroecosystem in Razavi Khorasan province mainly is because of good conditions of soil structure and higher yield of different crops such as forage, vegetables, industrial crops and cereals. Considering the total agroecosystem health the highest value observed in Razavi Khorasan followed by Sistan and Baluchestan, North Khorasan and South Khorasan. Based on our classification total agroecosystem health in South Khorasan province was very poor and in other provinces was poor. The main reasons for the low value of agroecosystem health in all of the studied provinces are: soil compaction, low rainfall, using traditional methods of irrigation, insufficient cultivation of forage and perennial crops and also nitrogen fixing legumes. The fertilizer use efficiency in all of the provinces is low and these conditions could be harmful either for human and environment health.
 
Conclusion
Based on results the total agroecosystem health in South Khorasan province was very poor whereas in other three provinces total agroecosystem health was poor. The main reasons for bad condition of agroecosystem health in these provinces are: soil compaction because of unsuitable use of agricultural machinery, the low amount of precipitations, nitrogen use efficiency and area under cultivation of perennial, forage and nitrogen fixing crops. It seems that solving these problem using different methods such as increasing agrochemical use efficiency, applying good rotation and increasing water use efficiency could improve the total agroecosystem health in the eastern provinces of Iran.
 Acknowledgements
The authors acknowledge the financial support of the project by Vice President for Research and Technology, Ferdowsi University of Mashhad, Iran.