GENESIS & RELEVANCE

Nitrogen is a vital element for growing healthy, high-yielding plants. While it makes up 70% of the air we breathe, nitrogen is unusable by plants in its native form. As a result, synthetic nitrogen fertilizers were developed to drastically increase agriculture productivity. This has come at cost to our environment -- industrially produced nitrogen fertilizers pollute waterways and are responsible for 3% of worldwide greenhouse gas emissions.

So could there be a way that science and innovativeness bring about a solution that enables plants to capture nitrogen autonomously without synthetic fertilizers? A natural process so to say?

Synthetic and nature- driven solutions

Today nitrogen is synthetically supplied to the plants in the form of nitrogenous fertilizers. The product is offered in the global market in various forms including calcium ammonium nitrate, ammonium sulfate, ammonia, and others, with different proportions of the nutrient values. Hydrogen and nitrogen are the crucial raw materials utilized in the fertilizer manufacturing process. The primary nutrient used in such fertilizers is nitrogen and plants require it in large quantities. It plays a significant role in photosynthesis and is thereby essential for plants to produce their food using sunlight. Also, it is necessary for nearly every aspect of plant physiology. Nitrogen deficiency in plants can lead to the development of yellow leaves and poor growth.

Nature has however endowed some plants like soybeans, peanuts, and other legumes with the unique capability of converting nitrogen from the air into a form they can absorb through their roots in a process called nitrogen fixation. These plants fundamentally take advantage of the microbes in the soil. In fact, these microbes are the unsung heroes of the natural growing process.

Nitrogen fixation- existing pathways  

By nature

Nitrogen is fixed, or combined, in nature as nitric oxide by lightning and ultraviolet rays, but more significant amounts of nitrogen are fixed as ammonia, nitrites, and nitrates by soil microorganisms. More than 90 percent of all nitrogen fixation is effected by them. Two kinds of nitrogen-fixing microorganisms are recognized: free-living (nonsymbiotic) bacteria, including the cyanobacteria (or blue-green algae) Anabaena and Nostoc and genera such as Azotobacter, Beijerinckia, and Clostridium; and mutualistic (symbiotic) bacteria such as Rhizobium, associated with leguminous plants, and various Azospirillum species, associated with cereal grasses.

By industrial means

Nitrogenous materials have long been used in agriculture as fertilizers, and in the course of the 19th century the importance of fixed nitrogen to growing plants was increasingly understood. Accordingly, ammonia released in making coke from coal was recovered and utilized as a fertilizer, as were deposits of sodium nitrate (saltpetre) from Chile. Wherever intensive agriculture was practiced, there arose a demand for nitrogen compounds to supplement the natural supply in the soil. At the same time, the increasing quantity of Chile saltpetre used to make gunpowder led to a worldwide search for natural deposits of this nitrogen compound. By the end of the 19th century it was clear that recoveries from the coal-carbonizing industry and the importation of Chilean nitrates could not meet future demands. Moreover, it was realized that, in the event of a major war, a nation cut off from the Chilean supply would soon be unable to manufacture munitions in adequate amounts.

During the first decade of the 20th century, intensive research efforts culminated in the development of several commercial nitrogen-fixation processes.

The three most-productive approaches were the direct combination of nitrogen with oxygen, the reaction of nitrogen with calcium carbide, and the direct combination of nitrogen with hydrogen. In the first approach, air or any other uncombined mixture of oxygen and nitrogen is heated to a very high temperature, and a small portion of the mixture reacts to form the gas nitric oxide. The nitric oxide is then chemically converted to nitrates for use as fertilizers. By 1902 electric generators were in use at Niagara Falls, New York, to combine nitrogen and oxygen in the high temperatures of an electric arc. This venture failed commercially, but in 1904 Christian Birkeland and Samuel Eyde of Norway used an arc method in a small plant that was the forerunner of several larger, commercially successful plants that were built in Norway and other countries.

Nitrogen Fixation Cycle