بوم شناسی کشاورزی (Jul 2021)
Evaluation of Environmental Consequences of Conventional Management for Agroecosystems in Khorasan Province
Abstract
Introduction[1]Ecosystem Services frameworks are emerging as an approach of capturing the wider impacts of policy decisions or evaluating land use change in order to more comprehensively take into account the range of effects on the environment, and on the benefits humans receive from. The Millennium Ecosystem Assessment (MA) (2005) defines ecosystem services as ‘‘the benefits that humans obtain from ecosystems”. Costanza et al. (1997) postulated that ecosystem services comprise of ‘‘flows of materials, energy, and information” from the natural environment to the society. Yield and production for agricultural crops have been improved during the last century, however, these achievements have caused different environmental social and safety problems for human and the environment such as increase in greenhouse gases, eutrophication of rivers, lakes and other water bodies.This study aimed to evaluate environmental consequences of agroecosystems managed conventionally in three Razavi Khorasan, South Khorasan and North Khorasan Provinces. The environmental consequences of intensive agriculture were grouped into damages maid to natural resources such as water, air, soil, biodiversity and human health affected by over-consumption of chemical fertilizer, herbicide and pesticide.Materials and MethodsCultivated area and consumption of chemical inputs in North Khorasan, South Khorasan and Razavi Khorasan provinces during 2004-2009 were determined. Environmental impacts were calculated using six categories i.e. air (emission of greenhouse gases such as N2O, CO2 and CH4 to the atmosphere), water (quality criteria such as NO3- and pesticide concentrations in water), soil (amounts of NO3-, organic carbon, pesticides and herbicides in soil), biodiversity (losses of pastures, jungles and bee hives), human health (residues of Diazinone, Azinophos-Methyl and NO3- in some vegetables) and natural resources (losses of nitrogen fertilizers via leaching and volatilization and pesticides consumption effects) affected by chemical inputs such as fertilizers, herbicides and pesticides.Results and discussionResults indicated that decreasing trends in use of chemical pesticide and herbicide were observed in different agroecosystems of Khorasan. Nitrate of water used in agricultural area was higher than allowable limit of 10 mg per liter. Residues of chemical herbicide including Diazinone and Azinophos- Methyl in irrigated water were 23.18±16.35 and 15.78±0.68 mg.kg-1, respectively. The maximum emission of greenhouse gases including CO2, CH4 and N2O were calculated in Razavi Khorasan. Nitrate concentration in the soil was higher than the critical limit. Organic carbon content in natural habitat and rangeland was higher than that in the cropland. Also, total number of honey hives was increasing but the hives for local bees were almost reaching to zero in the recent years. The maximum range of nitrate for tomato, eggplant, cucumber and spinach were 1.4, 0.75, 17.15 and 7.38% higher than allowable limit, respectively. For sugar beet upper and lower limits of nitrate were lower than the allowable limit. ConclusionSoil is a very slow forming resource, and similarly to other habitats and ecosystems, it is coming under intensifying pressures due to anthropocentric and industrial activities. Soil ecosystem services provide multiple benefits to all organisms.Nitrate concentration for leafy vegetable was higher than for kitchen garden plants. Nitrogen and phosphorus contents for soil in Razavi Khorasan were higher relative to North Khorasan and South Khorasan. Nitrogen enhanced soil carbon accumulation as it stimulates plant growth and its productivity. However, accumulation of soil carbon depends on the delicate balance between increased carbon inputs to soil from litter and enhanced soil respiration rates. Crop residues and manure are returned to the soil in traditional farming systems, improving soil ecosystem services and soil chemical, physical and biological characteristics. On the other hand, application of inorganic and chemical fertilizers to benefit crop yields often decreases the soil services as it has negative influences on soil structure, infiltration and water-holding capacity.
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