Impacts of inorganic nitrogen fertiliser on soil fertility and groundwater quality of Touba orchards (western Iran)

Input of nitrogen (N) fertiliser in agricultural systems is important for their sustainability. However, when N inputs are very high, the excess can contribute to environmental problems such as loss of soil fertility and groundwater pollution. Based on this hypothesis, a field trial was carried out in Touba orchards of the Kurdistan province (Western Iran) in 2009, which aimed at evaluation of soil and groundwater quality of the mentioned orchards. Soil samples were analysed to measure quality parameters including soil organic carbon (SOC), total nitrogen (TN), available phosphorous (P-av) and available potassium (K-av). Moreover, nitrate (NO3) concentration was measured in water samples and compared with WHO standards of drinking water (50 mg l(-1)). The obtained results of soil analysis showed that SOC is significantly higher (1.55 g kg(-1)) and lower (0.71) in the orchards of the Sanandaj and Qorveh counties, respectively. In addition, the results of hydrochemical analysis showed that NO3 concentration was in the range of 21-95 mg l(-1). Moreover, 90% of groundwater samples collected from the orchards of the Qorveh county, exceeded WHO standard level which is a reflection of N-fertiliser application at high rate (340 kg ha(-1)).Input of nitrogen (N) fertiliser in agricultural systems is important for their sustainability. However, when N inputs are very high, the excess can contribute to environmental problems such as loss of soil fertility and groundwater pollution. Based on this hypothesis, a field trial was carried out in Touba orchards of the Kurdistan province (Western Iran) in 2009, which aimed at evaluation of soil and groundwater quality of the mentioned orchards. Soil samples were analysed to measure quality parameters including soil organic carbon (SOC), total nitrogen (TN), available phosphorous (P-av) and available potassium (K-av). Moreover, nitrate (NO3) concentration was measured in water samples and compared with WHO standards of drinking water (50 mg l(-1)). The obtained results of soil analysis showed that SOC is significantly higher (1.55 g kg(-1)) and lower (0.71) in the orchards of the Sanandaj and Qorveh counties, respectively. In addition, the results of hydrochemical analysis showed that NO3 concentration was in the range of 21-95 mg l(-1). Moreover, 90% of groundwater samples collected from the orchards of the Qorveh county, exceeded WHO standard level which is a reflection of N-fertiliser application at high rate (340 kg ha(-1)).A