A nutrient cycle is a cyclic mechanism through which nutrients travel in order to be recycled and used. Cells, organisms, communities, and ecosystems are all included in the pathway of a nutrient cycle. This article will explain to you about Nutrient Cycling which will be helpful in preparing the Environment syllabus for the UPSC Civil service exam.

Nutrient Cycling - Concept

• Nutrients are absorbed, transported, released, and reabsorbed during this process. It's a natural mineral-nutrient recycling mechanism.
• After death and decomposition, nutrients eaten by plants and animals are returned to the environment, and the cycle continues.
• Microbes in the soil play a crucial role in nutrient recycling. They eat organic stuff and break down it to release nutrients.
• They are also necessary for trapping and transforming nutrients into the soil that can be absorbed by plant roots.
• The pace of nutrient cycling is influenced by a variety of biotic, physical, and chemical variables.
• The carbon cycle, nitrogen cycle, water cycle, and oxygen cycle are examples of nutrient cycles.

Nutrient Cycling- Types

Based on the Replacement Period

• Perfect Cycle: Nutrients are replaced at the same rate as they are used in a perfect nutrient cycle. Most Gaseous cycles are thought to be perfect cycles.
• Imperfect Cycle: Sedimentary cycles are imperfect because certain nutrients are lost from the cycle and become trapped in sediments, making them unavailable for immediate cycling.

Based on the Nature of the Reservoir

• Gaseous Cycle: The atmosphere or the hydrosphere serves as the reservoir in the gaseous cycle.
• Sedimentary Cycle: The reservoir in the sedimentary cycle is the Earth's crust.

Gaseous Cycles

Water, carbon, and nitrogen are the three most significant gaseous cycles.

Water (Hydrologic) Cycle

• The water (hydrological) cycle is the solar-driven continuous circulation of water in the Earth-atmosphere system.
• The atmosphere, oceans, lakes, rivers, soils, glaciers, snowfields, and groundwater are all key reservoirs for water in our world.
• Evaporation, transpiration, condensation, precipitation, deposition, runoff, infiltration, and groundwater flow are all processes that carry water from one reservoir to another.
• It also refers to the continuous flow of water between the land surface, oceans, and subsoil, as well as between species.
• The evaporation of water from the ocean's surface starts the hydrologic cycle.

*To know more about this topic, click this link Water (Hydrologic) Cycle

The Carbon Cycle

• Carbon, primarily in the form of carbon dioxide (CO2), is present in the atmosphere.
• A continual exchange of carbon between the atmosphere and organisms is referred to as the carbon cycle.
• The process of photosynthesis transports carbon from the atmosphere to green plants and ultimately to organisms.
• It returns to the atmosphere through the processes of respiration and decomposition of dead organic stuff. It is majorly a short-term cycle.

*To know more about this topic, click this link Carbon Cycle

The Nitrogen Cycle

• Nitrogen is a basic building unit of every living tissue and is a vital component of protein. It accounts for roughly 16 per cent of all proteins by weight.
• There are three primary phases in the nitrogen cycle: nitrogen fixation, nitrification, and denitrification.
• The atmosphere, hydrosphere, and lithosphere are all part of this cycle.
• Nitrogen fixation is an anaerobic (oxygen-free) process that converts atmospheric nitrogen (N 2) to NH 3. It is done by nitrogen-fixing bacteria.
• Nitrification is a two-step process. The ammonium ion (NH4+) is first reduced to NO2.
• The molecule is then further oxidized to produce NO 3. Bacteria in the soil play a role in both processes once again.
• Denitrification is the conversion of nitrates to nitrogen gas. Denitrifying bacteria work in a similar way to nitrogen-fixing bacteria.

*To know more about this topic, click this link Nitrogen Cycle

Sedimentary Cycle

• Sedimentary cycles are biogeochemical cycles that have the Earth's crust as their reservoir.
• Iron, calcium, phosphorus, sulphur, and other earthbound elements are all part of the sedimentary cycle.
• Sedimentary cycles differ depending on the element, but they all have a solution (or water-related) phase and a rock (or sediment) phase.
• Sedimentary cycles take a very long time to complete.
• Phosphorus cycle and Sulphur cycle are the most important sedimentary cycles.

Phosphorus Cycle

• Phosphorus circulates through rocks, water, soil, sediments, and organisms in a cycle.
• Rain and weathering cause phosphate ions and other minerals to be released from rocks throughout time.
• This inorganic phosphate is subsequently dispersed throughout the soil and water.
• Inorganic phosphate is taken up by plants from the soil. Animals may eat the plants after that.
• Phosphate is integrated into organic molecules such as DNA once it reaches the plant or animal.
• When a plant or animal dies, it decomposes, releasing organic phosphate into the soil.
• Bacteria that break down organic materials to inorganic forms of phosphorus can make organic forms of phosphate available to plants in the soil. Mineralisation is the name for this process.
• Phosphorus from the soil can end up in streams and, eventually, the oceans.
• It can be absorbed into sediments over time once it reaches that location.

Sulphur Cycle

• The majority of the world's sulphur is bound up in rocks and salts, or buried deep within oceanic sediments.
• Sulphur is also contained in the air we breathe. Both natural and human sources contribute to its presence in the atmosphere.
• Volcanic eruptions, microbiological activities, water evaporation, and decomposing organisms are just a few examples of natural resources.
• When sulphur enters the atmosphere as a result of human activity, it is primarily due to industrial activities that generate large amounts of sulphur dioxide (SO2) and hydrogen sulphide (H2S) gases.
• Sulphur dioxide reacts with oxygen to form sulphur trioxide gas (SO3), or with other chemicals in the atmosphere to produce sulphur salts, when it reaches the atmosphere.
• Sulphur dioxide can also form sulphuric acid when it reacts with water (H2SO4).
• Dimethyl sulphide, which is exhaled into the atmosphere by plankton species, can also be used to make sulphuric acid.
• All of these particles will either fall back to earth or will react with rain and fall as acid deposits.
• Plants will then absorb the particles, which will then be released back into the atmosphere, restarting the sulphur cycle.

Calcium Cycle

• Calcium is primarily found in the form of rock, minerals, or structural calcium embedded in the mineral crystal lattices of soil particles, and it is not easily available.
• The majority of calcium in the soil is insoluble unless it is 'weathered off' of minerals or bacteria break down organic materials into soluble calcium.
• Some calcium, however, is held loosely or securely on the soil or in the soil solution, and is available to plants and microbes.
• Animals, microbes, and plants decompose, and the calcium in their bodies is mineralized and released back into the soil.
• Roots also return minerals, carbohydrates, and other chemicals to the soil on a regular basis, including calcium.
• Calcium is adsorbed to the surface of clay and negatively charged organic particles in the soil because it is a positively charged ion. Positively charged ions (cations) bind to soil particles and are referred to as "exchangeable ions" because they can be exchanged with other ions in the soil solution.
• Calcium enters an organic phase when it is taken by plants or microbes. Calcium is constantly exchanged between plant roots, microbes, and soil in this form.
• Decomposers break down a plant, animal, or soil fauna after it dies, and calcium is released back into the soil in a soluble form.
• As a result, calcium alternates between the soluble (and available) and the insoluble (and unavailable) phases.

Importance of Nutrient Cycling

• Nutrient Cycling is required for the conversion of nutrients from one form to another so that they may be used by various organisms.
• For example, plants cannot take atmospheric nitrogen and must fix it and convert it to ammonium and nitrate before they can be used.
• Nutrient cycles help to keep the ecosystem in balance by storing nutrients for future use.
• Transfer of nutrients from one location to another for utilization happens through nutrient cycling, such as from air to soil or from water to soil.
• Living creatures interact with their surroundings' abiotic components through nutrition cycling.

Conclusion

Carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus make up all living beings, biomolecules and cells. These nutrients are necessary for life to exist. For life to exist, it is critical to recycle and replace nutrients in the environment on a regular basis. Nutrient cycles help to keep the ecosystem in balance by storing nutrients for future use.