Nitrogen cycle

Look up into the sky and you look through millions of air molecules, eighty percent of which are nitrogen molecules - two atoms of nitrogen bonded together. Nitrogen is found all over the planet, not just in the sky. It is in living things, air, water, even animal waste. It travels between living and non-living parts of our planet via a process called the nitrogen cycle, which is one of the Earth’s biogeochemical cycles. As humans change the way we live on the planet, the way that nitrogen moves around the Earth also changes. Nitrogen atoms may seem small enough to be easily overlooked. We look right through the ones in the air, do we not? Yet recent changes in the nitrogen cycle are causing a very noticeable effect on natural environments and human health. Lakes are clogged with aquatic weeds. Dead zones have formed in areas of the oceans where animals can not survive. Air pollutants that contain nitrogen are decreasing air quality and greenhouse gases that contain nitrogen are becoming more common. Below are two examples of how humans are changing the nitrogen cycle and how the changing nitrogen cycle affects humans and ecosystems. Fertilizing the Earth with Nitrogen Plants need nitrogen to grow. Plants are not able to use the nitrogen that is in the atmosphere for this, even though there is tons of it available. It’s just not in a form that plants can use. So they get the nitrogen they need from the soil where bacteria have converted it into a usable form. In natural co...

• ClearIAS • What we offer: • Free Resources • Premium Resources • Courses • All Courses • Prelims Programs • Mains Programs • Interview Programs • PCM • Prelims cum Mains: Target 2024 • Prelims cum Mains: Target 2025 • Prelims cum Mains: Target 2026 • Prelims cum Mains: Target 2027 • PTS • UPSC Prelims Test Series 2024 • UPSC PYQ GS • UPSC PYQ CSAT • Study Materials • ClearIAS Blog • FREE Study Materials • Guidance Articles • UPSC Books • UPSC PDFs • ClearIAS Courses • ClearIAS Mobile Apps • UPSC • UPSC • UPSC Syllabus • UPSC Exams • UPSC Results • UPSC FAQs • Toppers • Reviews • UPSC Toppers • What’s New? • Latest Updates • New Courses • Login What is the nitrogen cycle? How is nitrogen important to the earth and living organisms? Read to know more. Nitrogen is the most abundant element in our atmosphere- approximately 78% of the atmosphere, hence is crucial to life. Nitrogen is found in soils and plants, in the water, and the air. It is also essential to life as a key building block of DNA, which determines our genetics, is essential to plant growth, and therefore necessary for the food we grow. The balance of nitrogen is crucial for the environment and the life it sustains. When plants lack nitrogen, they become yellowed, with stunted growth, and produce smaller fruits and flowers. But when too much nitrogen is supplied it pollutes water systems and endangers aquatic life. Nitrogen is a chief constituent of the bodies of living organisms as the Nitrogen atoms are found...

Xuanyu Han / Getty Images There are two main ways nitrogen can become " • Fixation by lightning: The energy from lightning causes nitrogen (N 2) and water (H 2O) to combine to form ammonia (NH 3) and nitrates (NO 3). Precipitation carries the ammonia and nitrates to the ground, where they can be assimilated by plants. • Biological fixation: About 90% of nitrogen fixation is done by bacteria. Cyanobacteria convert nitrogen into ammonia and ammonium: N 2+ 3 H 2 → 2 NH 3. Ammonia can then be used by plants directly. Ammonia and ammonium may be further reacted in the nitrification process. Tony C French / Getty Images Nitrification occurs by the following reactions: 2 NH3 + 3 O2 → 2 NO2 + 2 H++ 2 H2O 2 NO2- + O2 → 2 NO3- Aerobic bacteria use oxygen to convert ammonia and ammonium. Nitrosomonas bacteria convert nitrogen into nitrite (NO2-), and then Nitrobacter converts nitrite to nitrate (NO3-). Some bacteria exist in a symbiotic relationship with plants (legumes and some root-nodule species), and plants utilize the nitrate as a nutrient. Meanwhile, animals obtain nitrogen by eating plants or plant-eating animals. Simon McGill / Getty Images When plants and animals die, bacteria convert nitrogen nutrients back into ammonium salts and ammonia. This conversion process is called ammonification. Anaerobic bacteria can convert ammonia into nitrogen gas through the process of denitrification: NO3- + CH2O + H+ → ½ N2O + CO2 + 1½ H2O Denitrification returns nitrogen to the atmosphere,...

• Fixation – The nitrogen in the atmosphere is in the inert form and only a few organisms can benefit from it. For it to be useful to all life forms, it should be converted to fixed or organic form. Hence, the process is called nitrogen fixation. The process of nitrogen fixation includes the following: • Nitrogen is deposited through precipitation. It comes from the atmosphere and deposited into the soil and water surface. • Once a deposit is successful, nitrogen will have some changes. The two nitrogen atoms separate and form into ammonia by combining with hydrogen. There are three organisms responsible for this action – algae, free anaerobic bacteria, and bacteria residing in a symbiotic relationship with some types of plants. (1, 2, 3, and 4) What to keep in mind? • Plants do not have the ability to use atmospheric nitrogen. They need the help of nitrogen-fixing bacteria. • Nitrogen depletion in soils is remedied by planting crops like beans and alfalfa. • Nitrogen can be fixed through man-made processes such as the creation of nitrogen and ammonia fertilizers. (2, 3, and 4) What are the microorganisms that play a role in the nitrogen fixation process? • Prokaryotes • Abiotic means such as lightning or some industrial interventions like combustion of fossil fuels. • Root exudates from legume plants such as clover, peas, and soybeans • Aerobic and anaerobic nitrogen-fixing bacteria • Phototrophic and chemotrophic bacteria (4, 5) Image 3: The nitrification process of the ...

Miriam R. Aczel I am a President’s Ph.D. Scholar at Imperial College London. My research looks at how drilling for shale gas (natural gas trapped inside shale rock) affects both human health and the environment. I am also the co-Founder and co-Director of the Amir D. Aczel Foundation for Research and Education in Science and Mathematics, which works to encourage young students in Cambodia to study science and math. I was born on Earth Day, so naturally I love being outside and look for any excuse to spend time with animals of all shapes and sizes! * Age: 14 My name is Juliette and I am a rising freshman. I learned how to play chess at an early age and I have been playing and competing since then. I also love to play tennis. In addition to English, I speak Spanish and Mandarin. At home, I have a hamster named Pumbaa, in reference to the warthog in Lion King. Abstract Nitrogen, the most abundant element in our atmosphere, is crucial to life. Nitrogen is found in soils and plants, in the water we drink, and in the air we breathe. It is also essential to life: a key building block of DNA, which determines our genetics, is essential to plant growth, and therefore necessary for the food we grow. But as with everything, balance is key: too little nitrogen and plants cannot thrive, leading to low crop yields; but too much nitrogen can be toxic to plants, and can also harm our environment. Plants that do not have enough nitrogen become yellowish and do not grow well and can have sm...

Nitrogen is a crucially important component for all life. It is an important part of many cells and processes such as amino acids, proteins and even our DNA. It is also needed to make chlorophyll in plants, which is used in photosynthesis to make their food. As part of these life processes, nitrogen is transformed from one chemical form to another. The transformations that nitrogen undergoes as it moves between the atmosphere, the land and living things make up the nitrogen cycle. Fixation Nitrogen in its gaseous form (N 2) can’t be used by most living things. (Plants for example, do not have the required enzymes to make use of atmospheric nitrogen.) It has to be converted or ‘fixed’ to a more usable form through a process called fixation. There are three ways nitrogen can be fixed to be useful for living things: • Biologically: Nitrogen gas (N 2) diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH 4 +), which can be used by plants. Legumes (such as clover and lupins) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria. (Learn more about this process in the article • Through lightning: Lightning converts atmospheric nitrogen into ammonia and nitrate (NO 3) that enter soil with rainfall. • Industrially: People have learned how to convert nitrogen gas to ammonia (NH 3 -) and nitrogen-rich fertilisers to supplement the amount of nitrogen fixed naturally. Decomposit...

Nitrogen exists in the atmosphere as N 2 \text N_2 N 2 ​ start text, N, end text, start subscript, 2, end subscript gas. In nitrogen fixation, bacteria convert N 2 \text N_2 N 2 ​ start text, N, end text, start subscript, 2, end subscript into ammonia, a form of nitrogen usable by plants. When animals eat the plants, they acquire usable nitrogen compounds. • Nitrogen is everywhere! In fact, N 2 \text N_2 N 2 ​ start text, N, end text, start subscript, 2, end subscript gas makes up about 78% of Earth's atmosphere by volume, far surpassing the O 2 \text O_2 O 2 ​ start text, O, end text, start subscript, 2, end subscript we often think of as "air". 1 ^1 1 start superscript, 1, end superscript But having nitrogen around and being able to make use of it are two different things. Your body, and the bodies of other plants and animals, have no good way to convert N 2 \text N_2 N 2 ​ start text, N, end text, start subscript, 2, end subscript into a usable form. We animals—and our plant compatriots—just don't have the right enzymes to capture, or fix, atmospheric nitrogen. Nitrogen enters the living world by way of bacteria and other single-celled prokaryotes, which convert atmospheric nitrogen— N 2 \text N_2 N 2 ​ start text, N, end text, start subscript, 2, end subscript —into biologically usable forms in a process called nitrogen fixation. Some species of nitrogen-fixing bacteria are free-living in soil or water, while others are beneficial symbionts that live inside of plants. ...