Investigation Of Nitrate Concentraion In Soil,Water And Plant On Agricultural Lands In Baraan Area Of Esfahan.

There is concern about harmful effect of excessive nitrate concentration of eatable plants, on human and animals’ health. Numerous studies have been taken on nitrate accumulation especially in vegetable plants throughout the world. Therefore, Studies are necessary for accessing the local nitrate content of vegetable crops in major production areas. The soil,water and vegetable nitrate level were studied in Northern Baraan (in 20 Km East of Esfahan in the old alluvial plain of Zayandeh-roud river in central part of Iran) for two years. The selected vegetables were consisted of leaf and stem vegetable including leek, dill, fenugreek (Trigonell), spinach, mint, sparsely and chiness parsley, bulb vegetable including onion, potato and tomato, fruit vegetable including the commonly grown melon of cantaloupes and cucumber. For each plant, 3 fields with similar cultural management were selected. In each field at the beginning and end of growing season soil top 0-30 cm, and irrigation waterwater were sampled in three replicates.Also eatable plant parts in three replicates, were sampled in the morning and afternoon.Soil nitrate concentrations in most of the vegetables fields were higher than permissible level, which shows excessive nitrogen fertilizer application. The results showed nitrate concentration in 75% and 79% soil study area were higher than permissible level of 20 mg/kg, in the first and second year, respectively. The nitrate concentration of the most irrigation well-water was higher than permissible range of 10 mg/l, which is the threshold limit for direct human and animal consumption, and land irrigation. The highest nitrate content in stem and leaf vegetable was found in sparsely (mean of 2121 mg/kg), and onion (mean of 238 mg/kg). The lowest nitrate concentration in leafy vegetable were found in spinach (mean of 20.8 mg/kg) and cucumber (mean of 89 mg/kg). The ranges of nitrate concentration in stem and leaf vegetable were 4 to 6297 mg/kg and in bulb vegetable were 17.3 to 872.4 mg/kg fresh weight. Nitrate content of all stem and leaf vegetable except spinach, bulb and fruit vegetable except cucumber were higher than permissible limit. Leafy, bulb and fruit vegetables nitrate concentration were higher than the permissible concentration level of 67-mg/kg fresh weight. The effect of time of plant sampling in the morning and afternoon on nitrate content was significant. Timing of sampling shows that Nitrate level in stem and leaf vegetable in the afternoon were significantly lower than morning and nitrate content decrease during the day.