Production of nitrogenous fertilizers were initiated when Fritz Haber and Carl Bosch in 1909 turned the nitrogen gas (N2) in the air into ammonia (NH3) through an industrial process. This conversion was a major breakthrough not only in industrialization but also in agriculture sector because prior to this conversion the main sources of fertilizer were animal dung, leaf litter, bird guano, etc which was not so productive and quick in action.
As the worlds population grew, it became obvious that we would need a cheaper, economic, quick and easier way to get a functional and usable form of nitrogen to grow our crops successfully to meet the food requirement of the people. So, supply of economical fertilizer has motorized food production ever since. But that sensational story is now becoming an environmental plague because in modern agriculture, the use of synthetic fertilizers, specifically inorganic-nitrogenous fertilizers, is increasing drastically to sustain crop yields. Now the N-fertilizers usage has raised about 20-fold over the last fifty years, becoming a major contributor of N2O emission and also to nitric acid, which is a source of acid rain. It is estimated that half of the total N-fertilizers are used in wheat, rice and maize with 16 per cent are applied only to rice. Along with causing ill effects to the plants, elevated levels of N2 also contaminate soil and fresh water sources with the accumulation of nitrate ions and disturb marine ecosystem and wild life. The demand for synthetic fertilizers is predicted to increase by 65 per cent by mid of the 21st century if present trends continue, which ultimately results in double amount of nitrogen released into the atmosphere and waterways. In ancient times, nitrogen made its from the environment into the living organisms through nitrogen fixation (somewhat from lightning strikes).
Now the natural nitrogen cycle is disrupted by the human made nitrogenous fertilizers which accounts for more than half of the annual amount of N-fixation attributed to human activity.
An additional amount comes from leguminous crops like soybeans and alfalfa (attractive hosts for N-fixing microbes) and enriches the soil where they are cultivated.
In addition to that nitrogen oxide formed during burning of fuels is also another contributor to nitrogen. Increasing rates of nitrogen usage in agriculture and other human made activities has doubled the amount of fixed nitrogen over the levels present during pre-industrial times which is ultimately worsening the green house effect, adding to smog, contaminating the fresh water, causing eutrophication and reducing the protective layer of ozone.
The amalgamation of increasing rates of fertilizer usage, draining of wetlands and floodplains and deforestation provide more area for crop cultivation which has disturbed the nitrogen cycle, especially abridged opportunities for the natural exclusion of nitrogen which consequently increases the amount of nitrogen in the estuary affecting both the quality of water and fish community. Furthermore, nitrogen is 298 times more potent than carbon dioxide (CO2) in prospective to global warming. Scientists are bothering about this flood of food may cause the slow- and -perhaps irreversible- demise of green and woodlands.
The writers are associated with the Agro-biology Lab, Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.