Abstract
Modern agriculture is now recognized by both farmers and environmentalists as a significant source of water pollution. Nitrates can cause "Methaemoglobinaemia (blue-baby syndrome)" and "Stomach Cancer" if intake increases from a certain limits. The world health organization (WHO) recommended the maximum admissible concentration (MAC) for drinking water is 11.3 mg L" N03-N (equivalent to 50 mg N03' L'\ Therefore a study was conducted in the Lysimeters measuring 4 x 4 x 4 feet to assess the N03-N concentration in water leached through Iysimeters soil by applying nitrogen fertilizer (NPK @ 120-100-50 kg ha-') and different irrigation levels. Three irrigation levels 7.5, 11 and 15 cm were applied to wheat in three irrigations. Leachate water was collected in containers beneath each Iysimeter plot and analysis of leachate obtained from Lysimeter plots showed that the N03 -N concentrations were well below the WHO standards. N03-N concentration ranged from 0.19 mg L" to 13.6 mg L" Total volume of water (rainfall plus irrigation) applied to wheat crop was also measured and during 2000- 2001 it was 1077 L, 1413 Land 1749 L; while during 2001-2002 it was 780 L, 1119 Land 1455 L from 7.5, 11 and 15 cm irrigation levels, respectively. The concentration of nitrates ranged from 1.26-8.66 mg L". The amount of total nitrates in leachate water were 980 mg, 1119 mg and 1405 mg in 2000-2001 and 534 mg, 465 mg and 759 mg from 7.5, 11 and 15 cm irrigation levels respectively. This study clearly showed that nitrate leaching occurred under higher irrigation frequencies but the N03-N concentrations in leachate were well below the WHO standards, so the pollution threat from nitrate leaching under Pakistan's existing conditions is not possible Key words: Nitrates, irrigation frequency, cereal foods, Pakistan.
