Key to Life, Risks and Cycle of Nitrogen

Abstract

Nitrogen is practically inert and largely unreactive, existing mostly in molecular form (N2) in the atmosphere and unsuitable for uptake by living matter. But it is one of the most commonly used practices to increase crop yields throughout the world because of the abundant availability of N fertilizers and their great effectiveness to increase yields compared with other organic fertilizers, such as manure and compost. It is essential to achieve production levels, which enable global food security, without compromising environmental security. Excessive application of N fertilizers in the last several decades, however, has resulted in undesirable consequences of soil and environmental degradations, such as soil acidification, N leaching to the groundwater, and greenhouse gas (N2O) emissions. Crop yields have declined in places where soil acidification is high due to the unavailability of major nutrients and basic cations and the toxic effect of acidic cations. Other disadvantages of excessive N fertilization include increased cost of fertilization, reduced N-use efficiency, and negative impact on human and livestock health. Diffuse pollution, caused by N fertilization in agriculture, has become a global problem that is difficult to solve. Nearly half of N fertilizer input is not used by crops and is lost into the environment via the emission of gases or by polluting water bodies. The N pollution level expected by 2050 is projected to be 150% higher than in 2010, with the agricultural sector accounting for 60% of this increase. So, to reduce these problems globally, understanding of nitrogen cycle and nutrient use efficiency is important.