What Is Humus, Benefits and How to Use It

What Is Humus
 
Humus is the substance that is left over after plants and animals have undergone a long process of thorough decomposition done by earthworms, bacteria, fungi, and other microorganisms. It is found in the top few inches of soil. The color of humus is brown or black, and it has a loose, crumbly, and spongy texture.
 
Humus contains the elements necessary for plant growth: nitrogen, phosphorus, sulfur, calcium, magnesium, and potassium. Depending on the original plant and animal material, the chemical composition of humus varies

11 Reasons Why Humus is Important for Soil 

1. Nutrient supply
 
Organic matter contains nutrients that are released after the breakdown by soil organisms. Studies indicate that two to three pounds of sulfur, 4.5 to 6.6 pounds of phosphorus oxide and 20 to 30 pounds of the macro-element nitrogen are released by every percent of organic matter found in the soil.
 
These elements released by the decomposed organic matter help in vegetative growth of a plant, amino acid production, support, anthocyanin formation, and chlorophyll production among other important functions that produce a healthy plant. Humus also supports the soil micro-organisms such as fungi, protozoa, bacteria, and algae among other species such as earthworms and insects that create a living component (soil ecosystem) which aid in the breaking down of nutrients.
 
The organisms break down the organic matter in the soil by ingesting and mixing them with the soil minerals the availing the nutrients to plants that are later consumed by primary consumers and up the food chain by humans. 

2. Water holding capacity
 
For the soil to be healthy, it must have enough moisture. It must also have a good water retention capacity according to different crop requirements. Organic matter provides the soil with the capacity to retain water. It acts like a sponge and it has the capacity to hold water, approximately 90 percent of its own weight. Water being held by the organic matter is readily available to the crops when needed. 

3. Cause soil aggregation
 
Soil aggregation is formed by clumping together of soil particles. Organic matter has the capability of causing the soil particles to clump together due to its adhesive properties to form soil aggregates. Soil aggregation improves soil structure which is also a property of healthy soil. 

4. Improves soil structure
 
Soil structure is the aggregation of soil particles in different patterns. A good soil structure is an indicator of healthy soil. One of the most significant factors affecting soil structure is the presence or absence of humus.
 
A soil with a high percentage of humus aggregates easily and, therefore, maintains a good soil structure. A soil with a low percentage of decomposed organic matter has poor structure and cannot support maximum crop production.

 
5. Prevention of erosion
 
The universal loss of soil equation data indicates that an increase in the overall decomposed soil organic matter from a percentage of one to three reduces erosion by approximately 20 to 33 percent.
 
Humus increases water infiltration which in turn helps in preventing surface runoff. Moreover, soil with a high amount of humus has a stable soil aggregate which makes it hard for the particles to be eroded by agents of erosion such as wind and water. 

6. Prevents leaching
 
Healthy soil is composed of minerals and nutrients required by the plant. However, due to adverse weather patterns among other factors, these nutrients and minerals can be leached to deeper depths where the crop roots may not reach, making them unavailable for soil use. But with the presence of decomposed organic matter, leaching is reduced.
 
The process of humidification involves action by microbes which secrete a sticky and gum-like mucilage. This mucilage is important in the formation of the crumby structure or tilth of the soil. It adheres the soil particles together and improves the aeration of different soils. Likewise, it increases chelation – a process where excess nutrients are bound to the decomposed organic particles of the humus and in turn prevent them from being leached.

7. Have a buffering effect
 
Different crops grow in soils of different pH levels. In this regard, good and healthy soil is one which can provide the optimum pH for specific plant growth, which is only possible when there is adequate humus in the soil. What is more, soil microbes thrive best in optimal soil pH. Humus has a buffering effect on the soil and prevents too much acidity or too much basicity.
 
Studies have also established that soils with a high percentage of humus are able to moderate the level of pH which allows plants to grow under optimum conditions as changes in the pH lead to low crop yields. 

8. Increases the oxidation of complex organic substances
 
The decomposition process of organic matter has a direct impact on the oxidation process of complex organic compounds such as the lignin-like humus. These compounds are broken down into simple sugars, amino sugars, aliphatic, and a type of acid referred to as phenolic.
 
These compounds are further broken down into microbial humus or biomass that are then transformed into humic assemblages after reorganization and further oxidation. The humic assemblages are the humic acid and the fulvic acids, which are crucial in binding to the metal hydroxides and minerals in the clay.

 
9. Improves poor soils
 
Humus has the ability to change the property of any given soil. Sandy soil, for instance, has poor water holding capacity, high drainage, and less soil microorganism and nutrients. Clay soil, a second example, has large aggregates that have good water holding capacity but with poor drainage and aeration.
 
Adding humus to sandy soil will increase its water holding capacity, increase nutrient concentration, and reduce leaching. Increasing the amount of humus in clay soil can help improve aeration, reduce water holding capacity, and increase nutrient content. Humus would also reduce the density of clay soils through the separation of its particles and allow air circulation as well as water permeation.
 
Further, the reduction of clay soil density can be done by mixing it with sandy soil. In fact, clay soil with a low amount of humus is virtually impenetrable due to its dense nature and if dry, it becomes difficult to work with it. Furthermore, the humus would also improve other soil aspects such as pH. 

10. Increases Soil fertility and acts as a food to microorganisms
 
Fertile soil is a soil that contains all the required nutrients in proper proportion for maximum growth of plants. Such soil has a good structure, texture, profile, optimum levels of pH and temperature, and all the necessary microbes.
 
A soil that is fertile is regarded as healthy for plant growth but it’s only termed fertile if it has humus. Therefore, humus plays a major role in soil structure, drainage, and pH moderation among other important soil characteristics.

 
11. Increases cation exchange capacity
 
The colloidal nature of humus helps it to increase the soil’s cation exchange capacity. The exchange makes the soil capable of storing nutrients through a process called chelation. During rainy seasons, the cations can be easily leached but with the presence of humus, they are held in place. 

 

How Humus Is Made

Humus can be made in two different ways: naturally and by humans collecting organic material—composting it—or leaving it in place and letting it decay to add to soil afterwards. Regardless of whether it’s Mother Nature or gardeners, the process of making humus is the same.
 
Piled up plant and animal materials decompose in a wide range of environmental conditions. In nature, humus is made over a longer period of time. For man-made humus, aeration, the right amount of moisture, and heat in a compost pile or bin speed up the decomposition process.
 
In the early stages of decomposition, some of the carbon, hydrogen, oxygen, and nitrogen in the decaying materials are released as water, carbon dioxide, methane, and ammonia, which creates the typical rotten compost smell. As the decomposition progresses, the organic materials are broken down further into more stable forms of nutrients that plants can use as food. 

Compost is man-made humus

Humus vs. Compost
 
Compost is one source of humus—the man-made kind. Humus, on the other hand, is the general term for fully decayed plant material that is naturally present in the top layer of soil or had been added by humans.
 
The organic materials in a compost bin are much more diverse from those that naturally accumulate in any given location from trees dropping leaves and other plant and animal waste. A compost bin is composed of an accumulation of food waste that you wouldn’t find in nature, that’s why balancing “brown” and green” materials, adding moisture, and turning the compost are important for successful composting.

 
How to Use Humus in the Garden
 
Humus is indispensable to plant growth but adding too much organic material or in the wrong form does more harm than good. Humus makes up only 3 to 6 percent of productive soil used for crops1. It is unlikely that with a yearly addition of humus to your garden, you risk of overloading the soil with more nutrients than the plants are able to use. The only reliable way to determine the nutrient content in your garden soil is a soil test, ideally two years in a row. That will give you a baseline to determine how the addition of humus is affecting the nutrient content.
 
Adding a lot of organic material that is not fully broken down, such as fresh wood chips, can lead to a temporary nitrogen deficiency2. As the number of bacteria in the soil increase and they work to decompose the organic material, they tie up nitrogen. Once the organic material is decomposed, the nitrogen is released back to the soil.