Living organisms are crucial for improving soil fertility primarily because their decomposition contributes to the formation of humus, a vital organic matter component of soil.
Here's a more detailed explanation:
The Role of Decomposition and Humus Formation
When living organisms, such as plants, animals, and microorganisms, die, their organic matter is broken down by decomposers like bacteria, fungi, and other soil organisms. This decomposition process transforms complex organic molecules into simpler substances. A significant product of this decomposition is humus.
Humus is a dark, spongy, amorphous, and complex mixture of partially decomposed organic matter. It plays several vital roles in enhancing soil fertility:
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Nutrient Reservoir: Humus acts as a reservoir of essential plant nutrients like nitrogen, phosphorus, and potassium. As humus slowly decomposes, these nutrients are gradually released into the soil in a form that plants can readily absorb.
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Improved Soil Structure: Humus improves the soil structure by binding soil particles together, forming aggregates. These aggregates enhance aeration, water infiltration, and drainage.
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Increased Water-Holding Capacity: Humus has a high water-holding capacity, meaning it can retain significant amounts of water in the soil, making it available to plants during dry periods.
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Enhanced Cation Exchange Capacity (CEC): Humus possesses a high CEC, which is the ability to retain positively charged nutrients (cations) like calcium, magnesium, and potassium. This prevents these nutrients from being leached out of the soil by rainfall.
Other Contributions of Living Organisms
Besides decomposition, living organisms contribute to soil fertility in other ways:
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Nitrogen Fixation: Certain bacteria, like Rhizobium, live in symbiotic relationships with leguminous plants. These bacteria convert atmospheric nitrogen into ammonia, a form of nitrogen that plants can use.
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Nutrient Cycling: Soil organisms participate in nutrient cycling by breaking down organic matter and releasing nutrients that plants can utilize.
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Burrowing and Tunneling: Earthworms, ants, and other burrowing animals create tunnels in the soil, improving aeration, drainage, and the distribution of organic matter.
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Mycorrhizal Associations: Mycorrhizal fungi form symbiotic relationships with plant roots, helping plants absorb nutrients like phosphorus and water from the soil.
In summary, living organisms play a pivotal role in creating and maintaining healthy, fertile soil through decomposition, nutrient cycling, and other processes that improve soil structure and nutrient availability.
