Why Should We Use Humic Acid?
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The main content of organic matter in the soil is humus. Humic acid, on the other hand, is the most active ingredient of humus. Today, the increasing use of chemical fertilizers has led to the rapid depletion of humus. However, humus is a substance that facilitates the uptake of fertilizers. In order to solve this problem, humic matter (humic acid and fulvic acid) applications have been started in recent years.
Soil organic matter is a term that includes all living, non-living or decomposed organic matter. Completely decomposed organic structures are called HUMUS. The best source of humus is decomposed plant or compost materials. Humates with high humic acid content are also a good and long-lasting source of humus. Humic substances can be divided into three main groups as shown in Figure; Fulvic acid, Humic acid and Humine.
HÜMİK MADDELER
As you move to the right in this table,
Color intensity increases
The degree of polymerization increases
Molecular weight increases
Carbon content increases
Oxygen content decreases
Acid exchange is reduced
Resolution decreases
Chemical Properties of Humic Substances
To briefly define these terms;
Humus: It is the basic substance that constitutes 65-75% of the soil. It consists entirely of decomposed organic matter. It plays an important role in soil fertility.
Humic substances: A chemical group consisting of the three organic residues humumin, fulvic acid and humic acid.
Non-humic substances: Insoluble and undecomposed organic substances such as resin, wax and organic acids.
Humates: Salts of humic acid.
Fulvic acids: Part of humic substances that are water soluble under all pH conditions. The color of fulvic acids is light yellow to yellow brown.
Humic Acids: Humic acids are the main compounds obtained from soil. They are dark brown-black in color. More than 60 different trace elements bound to naturally occurring humic acid molecules are readily available for use by various living organisms.
Humins: It is a part of humic substances that cannot dissolve in water at any pH value, acid or alkaline. Their molecular structure is very large. It is the most resistant to disintegration among humic substances.
What are Humic Acid and Fulvic Acid Sources?
As shown in the table below, humic and fulvic acids can be obtained from various sources. The highest humic and fulvic acid ratio is found in Leonardite. Leonardite was discovered to be a source of humic substances (humic + fulvic acid) in 1960. Researchers then started to apply these substances in agricultural fields.
Leonardite is the oxidized form of lignite coal formed as a result of a humification process lasting 70 million years. It has a high cation exchange capacity. Leonardite-derived humic acids are long acting. They do not compete with nutrients such as nitrogen. They are also used safely in organic farming.
When examined below, it is seen that leonardite has the highest content and value as humic and fulvic acid source.
Sources and proportions of humic and fulvic acids
All humic substances are persistent in the soil. Depending on environmental conditions, the half-life of fulvic acids varies between 10-50 years, while the half-life of humic acids is measured in centuries.
What are the Differences Between Humic Acid and Fulvic Acid?
As mentioned above, both fulvic and humic acids are formed when plant remains decompose. Both acids are useful for the soil and micro-organisms in the soil. Fulvic acid has a smaller molecular structure than humic acid. As a result, its persistence is less and it breaks down more easily. However, the rate of entry into the plant is higher in foliar applications. Humic acid, on the other hand, stays in the soil for a long time and breaks down slowly over time. In general, humic acids are utilized to increase the amount of soil organic matter due to their long-term effects.
How Humic Substances Benefit Sandy Soils
Sandy soils have an intermittent structure. In this type of soil, nutrients easily move downwards and cause economic losses for the producer.
Organic substances, humates, allow the soil to retain nutrients and the plant to benefit from them more easily. Humic substances are negatively charged and retain nutrients in the applied fertilizers and also retain water.
Humic substances retain nutrients through cation exchange capacity
How Humic Substances Benefit Clay Soils
Clay soils have a firm, water impermeable and heavy structure. This type of soil retains water in cold and humid weather conditions and shrinks and shrinks in hot weather. Both conditions are not favorable for plant growth.
When the soil begins to dry out, water molecules move away from the clay particles. This movement of water causes the clay particles to get very close to each other, their volume shrinks and cracks appear on the surface. Cracks on the surface are a common feature of clay soils with organic matter deficiency.
Adding humic acid to this type of soil improves the soil structure. Humic acid enters between the clay particles and prevents them from tightly joining and sticking in dry and hot weather. Large humic acid molecules can hold the clay particles separately and as a result, water and nutrients can easily settle in these areas. Figure 4 shows how humic substances improve and loosen the structure of clay soils.
What are the Other Benefits of Humic Acids?
The benefits of humic acids are categorized in three groups as physical, chemical and biological.
1-) Physical Benefits:
a) Improves the structure of the soil.
b) Increases the aeration properties of the soil. Provides better aeration of roots
c) Increases the water holding capacity of the soil. (It has the ability to hold water 20 times its own weight.)
d) It darkens the color of the soil and allows more solar energy to be absorbed.
2) Chemical Benefits :
a) Neutralizes soils with acidic and basic properties. It regulates the pH of the soil by removing excess salinity and excess lime.
b) It stores water soluble inorganic fertilizers in the root zone and releases them when the plant needs them.
c) It maximizes the cation exchange capacity of the soil.
d) Humic acid has a chemically active character and has the ability to form soluble or insoluble complexes with various metals, minerals and organics in the soil. This feature allows the plant to take nutrients easily and continuously. It helps to eliminate iron deficiency.
e) Has chelating properties.
f) It liberates carbon dioxide from the lime in the soil. This makes it possible to use the free carbon dioxide in photosynthesis.
g) It maximizes plant uptake of essential nutrients such as nitrogen, phosphorus, potassium, iron, zinc and trace elements in the soil.
h) It is rich in minerals (including trace minerals) and organic matter essential for plant growth. It also contains a lot of energy (up to 5,000 calories per 1 gram), which can be used for plant growth due to its natural carbon content.
ı) Humic acid, with its biochemical properties, cleans the soil of harmful, polluting and toxic substances. It ensures that lead, mercury, cadmium and other harmful and radioactive elements, industrial wastes, poisons and environmentally harmful chemicals (including those from pesticides) present in the soil change from soluble to insoluble. This prevents them from being absorbed by the plant. As these settle to the bottom over time, the soil is cleaned.
3) Biological Benefits:
a) It accelerates cell division. Therefore, the growth and development of the plant is also accelerated.
b) Accelerates root formation and development. It strengthens the roots. Promotes the formation of fringe roots.
c) Accelerates seed germination. It increases the plant's ability to survive. It makes the plants grow faster and stronger.
d) Increases cell energy in the plant.
e) Regulates plant metabolism and prevents the accumulation of nitrogen compounds.
f) It has a stimulating effect on the growth and reproduction of beneficial soil microorganisms. It increases their amount and activity in the soil.
g) Increases plant resistance to cold, heat and physical effects. Increases resistance against insects and diseases.
h) Increases the thickness of cell walls in fruits (product). This extends the storage time and shelf life of the product.
ı) The product obtained (such as fruit, vegetables, flowers, grains, roots) is of better quality. It ensures that their appearance is more attractive and their nutritional value is higher.
SOURCES 1. Burdick, E. M., 1965. “Commercial Humates for Agriculture and the Fertilizer Industry”. Economic Botany, Vol. 19, No:2:152-156. 2. Freeman, P. G., 1969. “The use of Lignite products as plant growth stimulants. Technology and use of Lignite”, IC Bureau of Mines Information Circular, 8471:150-153: 160:162:164. 3. Senn, T. L. And Kingman, A. R., 1973. “A review of Humus and Humic Acids.” Clemson University, Dept of Horticulture, Research Series No. 145, March. |
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Humic acid is the most active ingredient in humus.