Underground water having high concentration of nitrate can not be used as a source of nitrogen fertilizer. Such water is neither fit for irrigation nor for drinking purposes. Nitrates are invariably present in the underground water of Punjab. When irrigation water contains soluble nitrates, the effect of excess of N on most plants is quite discernible. High levels of nitrate may cause Iron (Fe) deficiency possibly due to reduced Fe activity in plant tissue by excess of organic anions. Forage crops and leafy vegetables when grown with water containing nitrate, accumulate high levels of nitrates and organic acids such as malate and oxalate to lower their food quality and may prove toxic to animals and human beings. The Environmental Protection Agency(EPA) has set the maximum contaminant level (MCL) of nitrate as nitrogen at 10 mg / L (or 10 parts per million) for the safety of drinking water. Nitrate at or above this level have been known to cause a potentially fatal blood disorder in infants undersix months of age called methemoglobinemia or "blue-baby" syndrome; in which there is a reduction in the oxygen-carrying capacity of blood.
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