Nov 08 - 14, 2004





Access to food supply is the greatest priority. Hence, agriculture is a dominant component of the global economy. The pressure to produce enough food has had a worldwide impact on agricultural practices. As the world population increases, croplands are unable to meet the growing demand for food without employing some method of crop enhancement. There are five common practices used to meet the growing demand: increasing tilled acreage, improving plant strains, introducing or expanding irrigation, controlling pest by chemical or biological methods, initiating or increasing fertilizer and pesticides usage.

Plants live, grow and reproduce by taking up water and mineral substances from the soil, carbon dioxide from the air and energy from the sun. Plants contain practically all-92 natural elements but need only 16 for proper growth. Apart from carbon, hydrogen and oxygen, plants take their nutrients essentially from the soil. These mineral nutrients are often classified into the primary plant nutrients, nitrogen, phosphorus and potassium, which are required by plants in large amounts; the secondary nutrients, calcium, magnesium and sulphur, which are need in smaller but still appreciable quantities; and the micronutrients, boron, chlorine, copper, iron, manganese, molybdenum and zinc. However, under current high yield production methods, soils are stripped of the essential nutrients, requiring the addition of fertilizers (primarily consisting of nitrogen, phosphorous, and potassium) to re-supply the land. Most of our soils have enough supplies of these minerals but intensive cropping and removal of crop residue from the farm have resulted in the reduced supply of the nutrients to plant. To make up the losses and deficiencies and to maintain these at satisfactory level for profitable farming, fertilizers are used.

In Pakistan, as well as in other developing countries, commercial agriculture is characterized by the use of high doses of chemical fertilizers, pesticides, herbicides, etc., which give quick and immediate returns for the investment made. This has led to increased consumption of fertilizers and consequently resulted in fertilizer related environmental hazard like nitrate pollution of ground water, increased emission of gaseous nitrogen and metal toxicity.

Although fertilizer nitrogen makes a great contribution to an increase in crop yields, excess fertilizer nitrogen is polluting groundwater with nitrate in areas where large amounts of fertilizer are used. In the country groundwater is an important source of drinking water, unfortunately in several areas the groundwater is polluted to an extent that it is no longer fit to be used as drinking water according to drinking water guidelines.

Nitrogen is comprised of the following forms (1) soluble organic N, (2) NH4-N (ammonium), (3) NO3-N (nitrate), (4) NO2-N (nitrite), and (5) N associated with sediment as exchangeable NH4-N or organic-N. Generally, soil N (held as protein in plant matter) and fertilizer-N are microbiologically transformed to NH4 (ammonium ion) through the process of ammonification. The ammonium ion is than oxidized by two groups of bacteria (Nitrosomonas and Nitrobacter) to NO3 with an unstable intermediate product NO2, in a process called nitrification.



Nitrogen is absorbed by plants in the form of either ammonium (NH4+) or nitrate (NO3-). Excess nitrates leach down the soil profile with percolating water. In our country nitrogen fertilizers are applied in form of Urea, which is readily hydrolyzed to ammonium ion (NH4). The ammonium ion (NH4) can be adsorbed to clay particles and moved with soil during erosion. More importantly, however, NH4 and NO3 are soluble and are mobilized through the soil profile to groundwater during periods of rain by the process of leaching. NO3 is also observed in surface runoff during rainfall events. Prevention of nitrogen pollution of surface and groundwater depends very much on the ability to maintain NO3 in soil only up to the level that can be taken up by the crop, and to reduce the amount of NO3 held in the soil after harvesting. An estimated 20 per cent of the nitrogen that humans contribute to watersheds eventually ends up in lakes, rivers, oceans, and public reservoirs.

Nitrate poisoning in the infant, can cause serious problems and even death. The lower acidity in an infant's intestinal tract permit growth of nitrate reducing bacteria that convert nitrate into nitrite, which is than absorbed into the bloodstream. Nitrite has a greater affinity for hemoglobin than does oxygen and thus replace oxygen in the blood complex. The body in denied essential oxygen and in extreme cases, the victim suffocates. Because the oxygen starvation results in a bluish discoloration of body, the nitrate poisoning is referred as blue baby syndrome (methemoglobinemia). Other health problems associated with nitrate toxicity include oral cancer, cancer of the colon, rectum or other gastrointestinal cancers, Alzeimer's disease, absorptive and secretive functional disorders of the intestinal mucosa and changes in maturation, differentiation and apoptosis in intestinal crypts. Infants and young children, people who are debilitated or living under unsanitary conditions and the elderly peoples are at greatest risk of these waterborne diseases. In the US, the upper limit for nitrates in drinking water is set at 45 ppm NO3- or 10 ppm NO3-N. The upper limit for nitrite nitrogen in public drinking water supplies is 1 ppm.

The escape of nitrate and phosphate from paddy fields into rivers and lakes via drainage canals, due to excessive fertilizer also courses eutrophication of surface water. Fertilization of surface waters (eutrophication) results in, explosive growth of algae, which causes disruptive changes to the biological equilibrium, including fish kills. Some species known as a "red tide" for its lurid colour, is form producing chemical toxins that kill fish and devastate commercial fisheries. Eating of shellfish tainted by a red tide, may causes skin irritation , liver damage, paralysis, and even death. Algal blooms due to excessive fertilizer in water, even when nontoxic, block out sunlight and cut off photosynthesis for plants living below. Then they die off and sink, depleting the water's supply of oxygen through their decomposition, this results in death of clams, crabs, and other bottom dwellers.

There are 10 fertilizer units operating in the country (Five units are in Punjab, three in Sindh and two in NWFP) with an installed capacity of 5.6 million tons, out of which nitrogenous fertilizer has a capacity of 4.9 million tons and phosphatic fertilizer has production capacity of 0.7 million tons. Most of these fertilizer units are located in agricultural belt. In addition Pakistan imports another 1.25 million tons for use in agriculture.

Wastewater streams from the nitrogenous fertilizer industry contain high levels of nitrogenous compounds such as ammonia, nitrates, and organic nitrogen. In ammonia production, wastewater is generated from process condensate stripping. wastewater is also generated in fertilizer production facility by leaks, spills, cleaning, maintenance, and laboratory tests. Cooling water contain ammonia, sulfate, chloride, phosphate, chromate, and dissolved solids, which become concentrated through evaporation. Typical source of wastewater generation in these fertilizer plants also includes, Intake water treatment sludge, demineralization plant effluents, cooling tower blow down, scrubber effluent, oily water from various sources in the plant; sewage from plant and residential colony. Most of the fertilizer units in our country are using earthen evaporation ponds for disposal of waster water having pollutant such as urea, ammonia, phosphate, sulphates, COD and oil in significant concentration, result in contamination of ground water body by infiltration. The permissible limit of ammonia in wastewater given in NEQS is 40 mg/l whereas standard of World Bank is 15 mg/l for ammonia discharge. The discharge of ammonia in the canal water above these ranges can be toxic to the aquatic life, if sufficient dilution does not occur. However, ammonia is being discharged from some factories at far higher concentration than prescribed in NEQS. The large volume of discharge has further aggravated the problem.

This high ammonia is reported to cause almost instant mortality to most forms of freshwater life. The fact that considerable urea quantity is also present, it indicates that even more ammonia will be generated during the decomposition process. The emissions of all forms of N contribute to aquatic eutrophication problems in the watershed. Nitrification of the ammonia, and ammonification of the urea followed by nitrification might result in excessive concentrations of nitrate in the water that is above standards set for drinking water.

Water samples taken from villages Downstream the urea plant near Daharki and Mirpure Mathelo had clearly shows high level of nitrate in ground water. Contamination of river water resulted in fish kill and paddy field damage. The community pressure for change is only moderate, as the plant's management having good relations with big landlords dominating the area. A detailed study of soil and groundwater is required to be carried to know the extent of soil pollution and groundwater contamination.

The urea and other particulate matter emissions in the shape of particulate matter from different unit especially prilling towers, where molten urea is converted into prill form, is common. The concentration varies from plant to plant depending upon the technology of prill towers. Fans on the prilling tower suck the air from the bottom of the prilling tower, comes into direct contact with molten urea to taken its heat. In the process part of urea is decomposed into ammonia and leaves the prillling tower with the leaving air without any form of filtration. Fine prills are also caught by the air flow and end up in the discharge air.

Ammonia gas is extremely corrosive and irritating to the skin, eyes, nose, and respiratory tract in high concentration. Exposure by inhalation causes irritation of the nose, throat, and mucous membranes. Lacrimation and irritation begin at 130 to 200 ppm, and exposure at 3000 ppm is intolerable. Exposure to high concentrations (above approximately 2500 ppm) is life threatening, causing severe damage to the respiratory tract, resulting in bronchitis, chemical pneumonitis, and pulmonary edema, which can be fatal. Eye contact with ammonia vapor is severely irritating, and exposure of the eyes to liquid ammonia or mists can result in serious damage, which may result in permanent eye injury and blindness. Skin contact with ammonia vapor, mists, and liquid can cause severe irritation and burns; contact with the liquid results in cryogenic burns as well. Ingestion of liquid ammonia burns the tissues, causing severe abdominal pain, nausea, vomiting, and collapse and can be fatal.

Use of unlined evaporation ponds is not environmental friendly solution for wastewater disposal because soil and ground water pollution is very much possible with this practice. It has been recommended to scrap these ponds and switch over to biological treatment plants. Emission from Prilling towers could be minimized by removing the contamination from leaving air with help of low pressure water scrubbers, or bag filters. Apart from this, it is recommended to change all pump seals pumping ammonia or liquids containing ammonia or with mechanical seals. This would reduce ammonia emission problem within the plant.

The proper implementation of NEQS and use of best available technology can minimize the contamination of water resources from the fertilizer plants. Controlling water pollution from agriculture is made difficult by its particular nature. In most circumstances, agricultural pollution occurs over a wide area, and its sources are diffuse and difficult to identify. It also varies unpredictably over time and space, and depends not only on rainfall patterns and the land slopes and soil characteristics but also on farmers' land use and crop choices, production techniques, and fertilizer and pesticide use. Farmers' decisions, in turn, are affected by market prices for inputs and outputs, as well as by governments' agricultural support policies.

Efficient fertilization is synonymous with the minimization of nutrient loss to the environment, without sacrificing crop yields or quality. Excess nutrients, from any source and especially nitrogen, not taken up by the crop, are likely to be lost to the environment and being at risk causing pollution. Evidently, if fertilization is to be efficient, it must be balanced and correct and, must be accompanied by other proper agricultural practices.

The improved methods of nitrogen fertilizer use, can minimize the nitrate leaching. This include substituting part of the inorganic fertilizers with organic fertilizers, Matching the plant needs and fertilizer applications by using appropriate split applications, Use of slow-release fertilizers (urea-aldehyde polymeric compounds, coated fertilizers), Choosing the right cropping systems, intercepting nitrate by means of trees or other deep rooted, nitrate mining crops (e.g. alfalfa) or by digging ditches, Establishment of information systems and monitoring networks, Education of the population in general and farmers in particular.

Sustainable agriculture is one of the greatest challenges. Sustainability implies that agriculture not only secure a sustained food supply, but that its environmental, socio-economic and human health impacts are recognized and accounted for within national development plans. FOA has defined the sustainable development as the management and conservation of the natural resource base and the orientation of technological and institutional change in such a manner as to ensure the attainment and continued satisfaction of human needs for the present and future generations. Such sustainable development conserves land, water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially acceptable.



Pollution control measures must rely heavily on approaches that affect farmers' land use and production decisions. Thus, agricultural policy, which directly influences these decisions, and environmental policy to control agricultural water pollution need to be coordinated and pursued with the same goals in mind. Policies that can affect farmers' land use and production decisions include voluntary measures such as education and training, moral suasion, and technical assistance; regulatory measures such as performance standards (maximum discharge rates or maximum pollutant levels) and direct controls on outputs, inputs, or technology.