How do you feel after spending long hours under the sun? Tired! Similarly you may have observed that leaves of plants droop if they are not watered regularly. Just as we need a nutritional diet and fluid to replenish ourselves similarly the soil too replenishes the nutrient needs of plants by supplying them with different minerals which is present in the soil. Sometimes when the soil has inadequate nutrients owing to overuse or some other natural reasons, the nutrients can be supplied in the form of manure and fertilizers. But usually the soil gets its nutrients back even after being constantly depleted due to extraction by the plants.
Soil is rich in nutrients. These nutrients are formed by the breaking of mineral carrying rocks and from the organic matter which is the decomposed part of animals and plants and their wastes. Once extracted, the plants and trees store these nutrients in its branches, leaves, stem, flowers and fruits. When leaves and branches of plants fall to the ground they decompose along with the other organic matter in the soil like feces of animals and insects and their dead bodies. Rainfall and earthworm mix these decomposed matter evenly with the soil and the soil is once again enriched with nutrients. This is basically how the nutrient cycle works.
Today due to too much clogging, saturation, pollution and over use of many natural resources we have reverted to recycling of things like paper or plastic. But in nature everything is recycled. Not a single thing created by nature is wasted and it can be easily recycled to its original form.
Carbon, Oxygen and Nitrogen along with water are the most important links of nutrient cycle. Each component has an independent cycle due to which the complete ecological system is balanced. These cycles are also called as bio-geochemical cycles wherein bio stands for life and geo stands for earth. Let us understand the different cycles like Carbon Cycle, Oxygen Cycle, Nitrogen Cycle and Water Cycle to get a clear knowledge about the nutrient cycle in totality.
Do you know that since childhood you have playing and learning with carbon? I am talking about the pencils we use. Pencils are made from graphite which is a carbon compound. Some other things which we use daily like gasoline or precious diamonds are made up of carbon. It is one of the most important elements of nature and all the living organisms on earth are made of carbon (humans too).
Carbon cycle begins with photosynthesis which combines sunlight, carbon dioxide from air and hydrogen from water to form carbohydrates. The food thus prepared is either used by plants for growth or stored for energy. When the animals eat plants the nutrients in the plants get digested and carbon is released through exhalation or respiration. Carbon is again released back into the atmosphere when the living organisms die as they decompose again to form carbon dioxide.
Nitrogen is an important element of ecosystem. But not very organism can use nitrogen directly. This is where the nitrogen fixing bacteria help by converting nitrogen into a usable form which can be absorbed by every organism. When the nitrogen is fixed it is available in the form of nitrates, nitrites and ammonia which can be easily absorbed by plants as nutrients. Once it gets converted into food, it is eaten by animals which are returned back to the soil in the form of feces and decomposed bodies of animals and plants.
Also there are denitrifying bacteria which balance the nitrogen level in the soil and if found to be excess convert the nitrogen compounds into nitrogen and release it back into the atmosphere.
Oxygen is main component of life on earth and earth’s atmosphere consists of 21 per cent of Oxygen. During photosynthesis oxygen is released as a by product by the plants while during respiration oxygen is taken in and water is released. Water is again absorbed by plants and the process starts all over again.
The cycle starts when water evaporates due to heat energy from the sunlight and becomes water vapor. This water vapor is responsible for cloud formation and rain. Rain thus returns back the water which assimilates in ground, river, seas, streams, ponds, lakes and oceans. This water is again absorbed by plants and released through photosynthesis in the atmosphere.