Nitrogen and Phosphorus Cycle

The nitrogen cycle involves several key processes that allow nitrogen, an essential nutrient for living organisms, to move through the environment:

• Nitrogen Fixation: The conversion of atmospheric nitrogen (N2) into ammonia (NH3) by nitrogen-fixing bacteria, making it available for uptake by plants

• Nitrification: The conversion of ammonia into nitrites (NO2-) and then into nitrates (NO3-) by nitrifying bacteria, which can be absorbed by plants

• Denitrification: The process by which nitrates are converted back into nitrogen gas (N2), returning nitrogen to the atmosphere and closing the cycle

Similarly, the phosphorus cycle is crucial for biological processes and includes the following steps:

• Weathering: The breakdown of rocks releases phosphate ions into the soil and water, making phosphorus available for plants

• Uptake: Plants absorb phosphates through their roots, incorporating them into biological molecules

• Decomposition: When plants and animals die, decomposition releases phosphorus back into the soil, where it can re-enter the cycle

• Sedimentation: Phosphorus can also be removed from the cycle through sedimentation, where it accumulates in ocean floors or lake beds, becoming part of sedimentary rocks over time

Basic Vocabulary

• Nitrogen- gas that makes up 78% of Earth’s atmosphere and is essential for life, it is a key component of amino acids and nucleic acids

• Phosphorus- an essential mineral for plant growth, it is found in rocks and minerals and is a key component of DNA, RNA, and ATP, playing a vital role in energy transfer

• Nitrogen Cycle- a series of natural processes by which nitrogen is converted between various forms

• Phosphorus Cycle- the process by which phosphorus moves through the lithosphere, hydrosphere, and biosphere, involving the weathering of rocks, uptake by plants, and return to the environment through decomposition

• Triple Bond- a strong chemical bond between two nitrogen atoms in molecular nitrogen

• Legumes- a group of plants that have symbiotic relationships with nitrogen

• Ammonification- the process by which bacteria or fungi convert organic nitrogen into ammonia (NH3NH3​)

• Immobilization- the conversion of inorganic forms of nitrogen or phosphorus into organic forms in microbial biomass, rendering these nutrients unavailable to plants

• Leaching- the loss of water-soluble nutrients from the soil due to rainfall or irrigation

• Eutrophication- the enrichment of an ecosystem with chemical nutrients, typically compounds containing nitrogen or phosphorus, that leads to excessive growth of organisms, particularly algae, which can deplete oxygen levels in water and harm aquatic life.

• Nitrification- the microbial oxidation of ammonia to nitrite, followed by the oxidation of nitrite to nitrate. It is a crucial step in the nitrogen cycle in soil

• Denitrification- a microbial process that reduces nitrate and nitrite to gaseous forms of nitrogen, such as nitrous oxide (N2ON2O) and nitrogen gas (N2N2)

• Assimilatory Nitrate Reduction- a process where plants and microorganisms reduce nitrate to ammonia for incorporation into organic molecules

• Anammox (Anaerobic Ammonium Oxidation)- a microbial process where ammonium and nitrite are directly converted into nitrogen gas in the absence of oxygen

• Mineralization- the decomposition of organic matter into inorganic compounds, making nutrients available to plants

• Volatilization- the loss of nitrogen from the soil as ammonia gas (NH3NH3​), especially under alkaline conditions, which can lead to reduced soil fertility and nitrogen availability for crops

• Guano- the accumulated excrement of seabirds and bats, often rich in phosphorus and nitrogen

• Apatite- a group of phosphate minerals, often the primary source of phosphorus in ecosystems

• Mycorrhizae- symbiotic associations between fungi and plant roots that enhance nutrient uptake, particularly phosphorus

• Limiting Nutrient- a nutrient that is in short supply, restricting growth or productivity in an ecosystem