Difference Between Water Cycle and Nitrogen Cycle

The key difference between water cycle and nitrogen cycle is that water cycle explains the changes of water between solid, liquid and gaseous phases while nitrogen cycle explains the conversion of nitrogen into its various chemical forms.

Matter cycling explains how matter moves through the living and nonliving components of the ecosystem. It is explained by different geochemical cycles. Water cycle explains the cycling of water while carbon, nitrogen, sulfur, phosphorus and oxygen cycles explain their movements on earth. Each individual cycle shows the cyclic exchange of material between living organisms and their non-living environment.

CONTENTS

1. Overview and Key Difference
2. What is Water Cycle
3. What is Nitrogen Cycle
4. Similarities Between Water Cycle and Nitrogen Cycle
5. Side by Side Comparison – Water Cycle vs Nitrogen Cycle in Tabular Form
6. Summary

What is Water Cycle?

Water cycle explains the changes or circulation of water between solid, liquid and gaseous phases. It also explains the physical movement of water through ecosystems.  From the total volume of water on Earth, more than 97% is saltwater that is present in the oceans. A small percentage is groundwater while less than 1% is freshwater.

 Sun is the main energy source that drives the water cycle. Liquid water converts into water vapour (gaseous phase) through the process of evaporation. Water vapour in the atmosphere then condenses into clouds and then falls off as rain to the ground via the process of precipitation. Moreover, liquid water converts into solid ice through freezing. Solid ice converts back into liquid water by melting. Ocean water evaporates and returns to lands as rain. Then from rivers and ground waters, water flows from lands to oceans via flowing through the surface (runoff) or percolation. Plants absorb water from their roots. From plants, water comes back to the atmosphere via transpiration.

What is Nitrogen Cycle?

The nitrogen cycle is one of the major biogeochemical cycles. It describes the conversion of nitrogen into different forms and its circulation through the ecosystems. Nitrogen mainly exists as nitrogen gas (N₂) in the atmosphere. The air in Earth’s atmosphere is made up of approximately 78% nitrogen. Nitrogen fixation is the key process that converts atmospheric nitrogen into nitrates in the soil. It is done by nitrogen-fixing bacteria. They use special enzymes called nitrogenases to fix nitrogen. Moreover, lightning can convert nitrogen gas into ammonium ions (NH₄⁺).

Ammonium ions are converted into nitrite (NO₂^–) by nitrifying bacteria. Furthermore, nitrites are converted into nitrates by nitrifying bacteria through a process called nitrification. Nitrate is the form of nitrogen that is usable by plant life. Plants uptake nitrates from the soil (assimilation). Animals eat plant materials which include nitrogen compounds. When plants and animals die, decomposers return nitrogen to the soil. Nitrate converts back into nitrogen gas in the atmosphere by a process called denitrification. It happens through the work of denitrifying bacteria.

What are the Similarities Between Water Cycle and Nitrogen Cycle?

• Water cycle and nitrogen cycle are two biogeochemical cycles.
• Both cycles represent how matter (water and nitrogen) moves through biological and physical components of the ecosystem.
• Water cycle plays a major role in cycling nitrogen and other cycles.
• Both cycles include natural processes.
• They are responsible for replenishing the ecosystem with nutrients necessary to sustain life.
• Both cycles work in balance.
• They are extremely important for the proper functioning of ecosystems.

What is the Difference Between Water Cycle and Nitrogen Cycle?

Water cycle and nitrogen cycle are two important biogeochemical cycles. The biogeochemical cycle that recycles water is the water cycle while the biogeochemical cycle that recycles nitrogen is the nitrogen cycle. So, this is the key difference between water cycle and nitrogen cycle. Moreover, the water cycle does not involve the action of bacteria while many processes of the nitrogen cycle are carried out by bacteria.

The below info-table summarizes the difference between water cycle and nitrogen cycle.

Summary – Water Cycle vs Nitrogen Cycle

Water cycle and nitrogen cycle are two main cycles of an ecosystem. Water cycle explains the recycling of water through the ecosystem. Nitrogen cycle describes the recycling of nitrogen through living (biotic) and non-living (abiotic) components of an ecosystem. Water changes its state when cycling while nitrogen changes its chemical form when cycling. Therefore, the nitrogen cycle is more complex than the water cycle. Thus, this is the summary of the difference between water cycle and nitrogen cycle.

Reference:

1. “The Water Cycle (Article) | Ecology | Khan Academy”. Khan Academy, 2020, Available here.
2. “The Nitrogen Cycle: Processes, Players, And Human Impact | Learn Science At Scitable”. Nature.Com, 2020, Available here.

Image Courtesy:

1. “The Water Cycle” By AIRS, the Atmospheric Infra (CC BY 2.0) via Flickr
2. “Nitrogen Cycle 2” By File:Nitrogen Cycle.svg: *By Cicle_del_nitrogen_de.svg: *Cicle_del_nitrogen_ca.svg: Johann Dréo (User:Nojhan), traduction de Joanjoc d’après Image:Cycle azote fr.svg.derivative work: Burkhard (talk)Nitrogen_Cycle.jpg: Environmental Protection Agencyderivative work: Raeky (talk) – Cicle_del_nitrogen_de.svgNitrogen_Cycle.jpg (CC BY-SA 3.0) via Commons Wikimedia