How Does Humus Improve Soil Health and Crop Productivity?
Humus is a black, organic substance that occurs in soil as plant and animal matter decomposes. Humus is the dark brown or black material that remains after the majority of the organic litter has decomposed. Earthworms also assist in the mixing of humus and minerals in the soil. Humus provides a variety of nutrients that are beneficial to soil health.
Humus soil component is one of the important features in the fertility of the soil.
In agriculture, "humus" may also refer to mature or natural compost that has been harvested from a forest or other naturally occurring source for use as a soil conditioner. It's also a term for a topsoil horizon that's rich in organic matter (humus type, humus form, humus profile).
Component of Soil
Minerals, liquids, gases, organic matter, and microorganisms make up soil, which is a porous medium. Soil is a complex natural body with properties resulting from the combined effects of climate and biotic activities, as changed by topography, acting on parent materials over time, according to the conventional description.
There are Five Components of Soil that are Present in the Ecosystem:
Minerals:
Sand and silt are examples of primary minerals, which are soil materials that are identical to the parent material from which they formed. They usually have a round or irregular shape. Secondary minerals, on the other hand, are formed when primary minerals are weathered, releasing essential ions and forming more stable mineral types like silicate clay.
Water:
The ability of a soil to retain water is primarily determined by the texture of the soil. The more small particles there are in the soil, the more water it can hold. As a result, clay soils have the highest water-holding ability, while sands have the lowest. Because of organic matter's high affinity for water, it also affects the water-holding capability of soils. The higher the amount of organic material in the soil, the greater the ability of the soil to retain water.
Organic Matter:
Organic matter is made up of dead plants and animals, and as a result, it has a high capacity for retaining and/or providing essential elements and water for plant growth. Soils with a high organic matter content often have a high CEC, making them some of the most beneficial for plant growth. Organic matter also has a high “plant available” water-holding capacity, which can help soils with low water-holding capacity, such as sand, develop more.
Gases:
The next most basic part of the soil is gases or air. Since air can fill the same spaces as water, it can make up anything from 2% to 50% of the volume of soil. Root and microbe respiration are both dependent on oxygen, which aids plant development. Belowground plant functions, such as nitrogen-fixing bacteria, depend on carbon dioxide and nitrogen.
Microorganisms:
Microorganisms are the final basic element of soils, and although they are abundant in the soil, they account for less than 1% of the total amount. The main decomposers of raw organic matter are microorganisms. Decomposers convert raw organic matter into humus, which is rich in readily available plant nutrients, by consuming organic matter, water, and air.
Humification:
Microorganisms decompose a substantial portion of the organic matter in the soil, converting it to inorganic minerals that plants' roots can consume as nutrients. Mineralization is the term for this method. Nitrogen (nitrogen cycle) and other nutrients (nutrient cycle) in decomposed organic matter are recycled in this process. Depending on the conditions of decomposition, a portion of the organic matter does not mineralize and is instead converted into concatenations of organic polymers through a mechanism known as "humification." These organic polymers are stable and makeup humus because they are immune to the action of microorganisms. This consistency means that humus becomes part of the soil's permanent structure, strengthening it.
Benefits of Soil Organic and Humus
The conversion of soil organic matter to humus feeds the population of microorganisms and other creatures in the soil, ensuring high and stable soil life levels.
The rate at which soil organic matter is converted to humus promotes (when fast) or inhibits (when slow) plant, animal, and microorganism coexistence in the soil.
Effective humus and stable humus are both additional sources of nutrients for microbes, with the former acting as a short-term storage reservoir and the latter as a long-term supply.
Humus is a colloidal material that boosts soil's cation exchange potential, allowing it to store nutrients by chelation. Although these nutrient cations are available to plants, they are retained in the soil and are not washed away by rain or irrigation.
Humus can retain the moisture equivalent of 80–90% of its weight in water, increasing the soil's ability to survive drought.
Humus' biochemical composition allows it to buffer, or moderate, excessively acidic or alkaline soil conditions.
Humus' dark colour, which is normally brown or black, aids in the warming of cold soils in the spring.
Humus can help to mitigate climate change because of its ability to sequester carbon.
FAQs on Humus Soil Component: Functions & Importance
1. What exactly is humus and how is it formed in the soil?
Humus is the dark, rich, organic component of soil that results from the complete decomposition of plant and animal matter. It is formed through a process called humification, where soil microorganisms like bacteria and fungi break down dead leaves, roots, and animals. This process transforms the raw organic material into stable, complex substances that are crucial for soil fertility.
2. What are the most important functions of humus for soil health?
Humus performs several vital functions that are essential for healthy soil and robust plant growth. Its key roles include:
Nutrient Reservoir: It acts like a sponge for essential plant nutrients such as nitrogen, phosphorus, and sulfur, releasing them slowly for plant uptake.
Water Retention: Humus can hold a significant amount of water, which helps soil remain moist and protects plants during dry periods.
Improved Soil Structure: It helps bind soil particles together into aggregates, which improves soil aeration, drainage, and prevents compaction.
Supports Microbial Life: It provides a source of energy and nutrients for beneficial soil microorganisms, which are vital for a healthy soil ecosystem.
3. What is the main difference between humus and compost?
While related, humus and compost are not the same. Compost is a mixture of decaying organic matter at various stages of decomposition. It is the product you get from a compost bin. Humus, on the other hand, is the final, stable, and fully decomposed end-product of this process. Essentially, compost contains humus, but it also contains other materials that have not yet fully broken down.
4. What are some practical ways to increase the amount of humus in garden soil?
You can increase the humus content in your soil by regularly adding sources of organic matter. Effective methods include spreading a layer of mulch (like wood chips or straw) over the soil, mixing in finished compost, and planting cover crops (like clover or vetch) that are later tilled into the soil. These practices provide the raw materials for microorganisms to create more humus over time.
5. Why is humus considered a more stable source of nutrients than raw organic matter?
Humus is considered a more stable nutrient source because it consists of complex, large molecules that are resistant to further rapid decomposition. This stability means it releases nutrients slowly and steadily as it mineralises. In contrast, raw organic matter like fresh grass clippings decomposes very quickly, releasing a sudden burst of nutrients that can be lost (leached) from the soil by rain before plants can use them all.
6. What are the consequences for soil that is low in humus?
Soil with low humus content suffers from several problems. It tends to be compacted and hard, with poor aeration and drainage. It cannot hold water effectively, making it prone to drying out. Furthermore, it has low fertility because it lacks a natural reservoir of essential plant nutrients and cannot support a healthy population of beneficial soil organisms. This results in poor plant health and reduced crop yields.
7. How do microorganisms specifically contribute to the formation of humus?
Microorganisms are the primary agents of humification. Initially, they rapidly consume simple compounds like sugars and starches from dead organic material. They then work on more complex materials like cellulose and lignin. Through their metabolic processes, they break down these structures and re-synthesise them into the very large, complex, and stable molecules that make up humus. This biological transformation is what turns decaying matter into a valuable soil component.
8. Are there different types of humus found in soil?
Yes, based on the environment and the degree of incorporation into the mineral soil, humus can be classified into three main types:
Mor: Found in acidic, coniferous forest soils. It forms a distinct layer on the soil surface and is not well-mixed.
Moder: An intermediate type where the humus is loosely mixed with the mineral soil.
Mull: Found in fertile, deciduous forest and grassland soils. It is well-mixed with mineral particles, rich in nutrients, and supports high biological activity.
