Nitrate concentrations in some vegetables and soils in Hamadan, western Iran

Excessive use of nitrogen (N) fertilizers contributes to the accumulation of nitrate () in soil and vegetable crops. Vegetables contribute considerably to human intake in Iran. This study was carried out to determine in vegetable crops and soils. Samples of different vegetables (edible portions) were taken from eight fields during spring, summer and autumn. Also samples of two soil depths (0–30 and 30–60 cm) were collected at sites corresponding to the vegetable field locations. The results showed a high variation of the content in various vegetables. Nitrate levels within the same vegetable, but in different fields also varied greatly. Different levels were found in different vegetables analyzed in different seasons. In general, higher levels were found in vegetables growing in spring and autumn. Spinach, radish and cress accumulated much higher levels than that of other studied vegetables. Nitrate concentration in soils also varied in different seasons. The results showed that continuous vegetable cropping caused accumulation of in soil, with a nitrogen (N) accumulation of 81 mg -N kg−1, on average. The soils were sandy loams and there is the possibility of excessive leaching from these vegetables fields. This has caused concern because of possible groundwater pollution. Poor fertilizer, irrigation, and soil management resulted in low fertilizer-use-efficiency and substantial losses of the applied N fertilizer to the groundwater.