Nutrient Cycles

A set of flashcards covering key terms and definitions related to nutrient cycles, their processes, and their impact on ecosystems.

Nutrient Cycles

The processes in ecosystems that recycle elements essential for life, such as nitrogen and phosphorus.

Saprobionts

Microorganisms that decompose dead organic matter, returning essential nutrients to the soil. In the nitrogen cycle, they play a vital role in ammonification by performing saprobiotic nutrition.

Mycorrhizae

Symbiotic relationships between fungi and plant roots that facilitate the uptake of water and inorganic ions by plants, thereby enhancing nutrient absorption.

Nitrogen Fixation

The process by which nitrogen gas (N2) from the atmosphere is converted into ammonium compounds (NH4^+) by nitrogen-fixing bacteria, making nitrogen available for plant use.

Ammonification

The conversion of nitrogen from dead organic matter (proteins, nucleic acids) and waste products (urea) back into ammonia (NH3) by saprobionts (bacteria and fungi). This ammonia then forms ammonium ions (NH4^+) in the soil and is a key step involving saprobiotic nutrition.

Nitrification

The process performed by nitrifying bacteria in which ammonium ions (NH4^+) are oxidized first to nitrites (NO2^-) and then to nitrates (NO_3^-). Nitrates are the primary form of nitrogen absorbed by plants.

Denitrification

The process of converting nitrates (NO3^-) back into nitrogen gas (N2) by denitrifying bacteria, typically under anaerobic conditions, which returns nitrogen to the atmosphere.

Phosphorus Cycle

The movement of phosphorus through the lithosphere (rocks), hydrosphere (water), and biosphere (living organisms and soil), involving processes like weathering of rocks, absorption by plants, consumption by animals, and decomposition.

Use of Fertilizers in Agriculture

Natural and artificial fertilizers are applied to agricultural land to replenish mineral ions, especially nitrates and phosphates, that are lost from the soil when crops are harvested and livestock are removed, ensuring soil fertility and crop productivity.

Natural Fertilizers

Organic materials, such as manure, compost, and guano, which are derived from dead organic matter. They release mineral ions slowly into the soil as they decompose.

Artificial Fertilizers

Inorganic chemical compounds manufactured to contain specific, concentrated proportions of essential mineral ions, such as nitrates (NO3^-), phosphates (PO4^{3-}), and potassium salts, designed for rapid plant uptake.

Environmental Issues from Fertilizer Use

The excessive or inappropriate application of both natural and artificial fertilizers can lead to significant environmental problems, primarily leaching and eutrophication.

Leaching

An environmental issue where excess soluble mineral ions, particularly nitrates, from fertilizers are washed out of the soil by rainwater and runoff into rivers, lakes, and groundwater, potentially causing water pollution.

Eutrophication

An environmental problem caused by the enrichment of water bodies with excess mineral ions, mainly nitrates and phosphates, from fertilizers. This leads to an excessive growth of algae (algal blooms), reduced light penetration, death of submerged plants, subsequent decomposition by saprobionts, and ultimately oxygen depletion, causing a decline in aquatic life.