The primary aim of our nation after independence was to achieve self support in food production. We used various inputs or resources and incorporated various means of stabilizing the yield of agricultural crops through incorporating fertilizers, pesticide and other toxic chemical besides improving the quality of the agricultural products. Though it helped our nation in producing the food to meet the needs of ever increasing population but besides this the use of unsustainable path to increase the food caused some severe concerns such as ground water pollution. Water is a vital component of life and very important to maintain the ecological balance to sustain civilization and for economic development. To overcome the problem of ground water pollution it is the need of the hour for making planning and management of water resources. Ever increasing population and escalating economic development exert increasing strain on water demand for various needs such as agricultural, domestic and industrial etc.
Groundwater is one of the imperative resources and is being tapped for irrigation and public health water supplies to facilitate drinking water. On the other hand, quality of water resources is getting ruined with increasing daily use of the fertilizers with the aim to sustain the productivity. The quality of both surface water in the rivers and groundwater is getting degraded due to disposal of municipal waste water, industrial water pollution, and drastically due to increasing use of agrochemicals. In addition to the problems of desertification, water logging, salinity and erosion that affect irrigated areas, the problem of increasing downstream degradation of water quality caused by accumulation of salts, agrochemicals and toxic leachates due to the application of fertilizer is a serious environmental problem. It is relatively recent detection that salinization of water resources is a foremost and widespread phenomenon of possibly even greater concern to the sustainability of irrigation than is that of the salinization of soils. In fact, only in the past few years it has become evident that incorporation of trace toxic constituents through application of fertilizers in agricultural drainage waters may cause downstream pollution problems that is making threat for prolongation of irrigation in future projects.
Out of the total nutrients, nitrogen is the main and important one being used in highest proportion. By applying a high amount of nitrogen, only small amount of it can be used efficiently and significant amount escapes into the air or seeps into the soil and move into the ground water resulting in a host of environmental and human health problems from climate change and dead zones in the oceans to cancer and reproductive risks. Out of the total application of nitrogen, crops utilize only 25 to 71 per cent while rest of the applied nitrogen either remains in the soil or is lost through leaching into the ground water that causes deterioration of the water quality and some is lost through denitrification and ammonia volatilization. Nitrogen reaches the environment of water by three ways – drainage, flow and leaching – and increased amount of the nitrate accumulation in some arid and semi-arid regions along with evaporation of water and that accumulated amount of nitrate leaches down in water in varying amounts and reaches in deep soil. In the soil, fertilizers convert to nitrate through nitrification by microorganisms. Due to negative charge of nitrate, it can reach the ground water. Even if the condition is ideal for application of fertilizer, plants use only 50 per cent of the applied nitrogen and 15-25 per cent react organic compounds in the clay soil, 2-20 per cent lost through evaporation and the remaining 2-10 per cent interferes into surface and groundwater.
The greater part of nitrogenous fertilizers isnt absorbed products and they interfere with both underground and surface water. A massive amount of applied fertilizer is wasted through percolation as nitrate and moves in to the underground water. The higher concentration of nitrate is producing the problem of cancer and blue babies. When nitrate level increases beyond 22.6 mg/L Nitrate-N in drinking water than it become the source for creation problem of blue baby syndrome (is a disease of bottle-fed infants). The production of the methaemoglonin produced by reaction of oxygen carrying hemoglobin with nitrate which results in hamper of transportation of oxygen causing infants to appear blue. Furthermore, higher concentrations of nitrate also badly affect the central nervous system. High levels of nitrate in ground water have association with gastric cancer, nervous system impairment and birth defects. For adults, 50 mg/L concentration of Nitrate-N in underground water is enough to cause gastric cancer. A positive correlation has also been found between nitrate concentration and liver cancer.
High concentration of the nitrate also affects the aquatic life of fish and other organisms by creating suffocation for them. Most of the applied fertilizers move into the ground water where it produces the algal bloom that starves water of oxygen and create the condition of suffocations for fish and other aquatic life and creating huge “dead zones” in lakes and oceans. Nitrate-contaminated water is also linked to reproductive problems, urinary and kidney disorders, and bladder and ovarian cancer. Excess nitrates in the soil sometimes convert to nitrosamines, which have been shown to cause tumors in laboratory animals.
The evaluation of water quality Para-meters during the last 13 years indicated that pH of water samples shows great variation from 6.84 to 7.27. High pH of irrigation water is a function of high carbonate and bicarbonate concentration. The concern for groundwater pollution is growing day by day. Due to these harmful effects of high nitrate concentration groundwater remediation is very expensive and usually not feasible, so prevention of pollution is the key to the solution.
“How to avoid this dangerous situation and what should be the mitigation strategies?” is now a question for the scientists. A feasible and viable check on this problem can be initiated as first assessing and marking the areas which are more susceptible to become infected as a result of excessive use of Nitrogenous fertilizers. Once identified these areas could then be forced with controlled fertilizer use or may become focus of attention at preventing contamination of the underlying groundwater sources. The pollution susceptibility maps of the affected regions of the nation can be helpful for both land-use planning and for groundwater quality monitoring. They may also provide information to law-makers, land-use planners and developers regarding the spatial distribution of the vulnerability to the pollution. The most important and first step in implementing groundwater management programmes is the construction of ground water pollution map. The more we delay it now, the more difficult it will be for us to preserve our fragile natural resources in future. The recognition of the susceptible area is the key need of our country. Susceptible areas should get rigorous efforts to make best use of nitrogenous fertilizers and enhance fertilizer use efficiency to lessen the threat of nitrate pollution from fertilizers. The application rates should be accustomed to make certain both optimum crop yields and permissible nitrate leaching loss and it must be followed through strict laws so as to safeguard our basic human right to safe drinking water.
The authors are associated with the Agro-biology Lab, Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.