We have already talked about amino acids and their importance. In addition to them, humic and fulvic acids are necessary for the proper growth and development of plants, which are no less important for the plant world.
Humic and fulvic acids are found in humus, they are an integral part of it and have a very beneficial and stimulating effect on plants. To begin with, a brief overview of the very definition of hummus.
Humus is a fertile soil that is located on the surface of the earth’s crust, with a small thickness, usually a few decimeters. It consists of a mixture of organic and mineral matter with the presence of bacteria. In the process of decomposition of extinct plant and animal remains, the very important organic matter humus (lat. humus-black earth) is created, which is the most important for soil fertility. The content of humus in the soil decreases with depth, and its fertility also decreases with the depth of the soil. It takes from several hundred years to a millennium for the formation of humus, because the process of humification in nature is very slow. There is an average of 5% of humus on the whole planet and it has different properties.
The organic matter that we add to the soil in the form of organic fertilizer reacts with compounds that are already in the soil. During this reaction, humic substances are formed – large molecules of organic matter with specific properties. A mixture consisting of 80-90% humus matter and 10-15% minor by-products resulting from the decomposition of organic matter is called humus .
Humus binds parts of clay and powder into larger structural aggregates, improving the water-air capacity of clay soil. Humus can bind 5-10 times more water than clay minerals and thus increase the absorption capacity of the soil. This feature of humus is important for all types of soil, especially sandy soil.
Humic substances have a great ability to bind nutrients in a form that is accessible to plants.
In the chemical sense, humic substances can be divided into three groups of organic substances: humic acids, fulvic acids and humin.
Many decomposition by-products such as auxins, vitamins, low-molecular acids, formed by the decomposition of organic matter (eg succinic acid), amino acids of microbial origin, also physiologically affect plant growth. These substances are growth and development stimulators, and are also a source of oxygen for plants. Numerous experiments have proven that fulvic and some humic acids have a positive effect on the growth of plants and the development of microorganisms, and they also play a very important role in the uptake of iron and other microelements from the soil.
Biostimulators (growth enhancers)
Plant biostimulators are various substances of natural origin that are used in agriculture to improve plant growth. They act by stimulating natural processes in the plant that enhance nutrient uptake, nutrient efficiency, tolerance to abiotic stress and improve crop quality.
Biostimulators do not have a direct effect on plant pests and pathogens, so they are not considered pesticides. Plants treated with biostimulators are not less attacked by pests, but less exposed to unfavorable conditions than untreated plants, but the impact of pests and pathogens on treated plants is lower due to better uptake of nutrients, translocation of nutrients and their use, and faster recovery from injuries caused by possible abiotic stresses (Calvo, 2014).
Biostimulators used in agriculture are divided into: microorganism inoculants, humic acids, fulvic acids, protein hydrolysates and amino acids, seaweed extracts.
Humic substances are substances that arise from physical, chemical and biological humification of biomolecules. Approximately 80% of the total carbon (C) content and 60% of the carbon (C) dissolved in water is a component of humus matter. Humic substances play an important role in maintaining soil fertility, thus influencing the production and cultivation of plants.
According to Pena-Mendez et al. (2005) humic substances are divided into three groups: humic acid, fulvic acid and humin. Humic and fulvic acids represent humic substances that are soluble, while humin is an insoluble humic substance, ie humin is considered to be a salt of humic acids.
The chemical structure of humic substances is very complex and depends on their origin. The main elements that make up humic and fulvic acid, regardless of origin, are carbon 52-60%, hydrogen 3-4%, oxygen 32-38%, nitrogen 4-5% and sulfur 0.4-0.6%.
Humic acids improve soil fertility, stimulate plant growth and disease resistance. They contain about 56% carbon (C) and are dark brown to black in color
Fulvic acid contains less carbon (C) around 34% and is brown to reddish in color. It contains more acid functional groups, especially -COOH. The total acidity of fulvic acid (900-1400 mmol / 100 g) is much higher than the total acidity of humic acid (400-870 mmol / 100 g) (Pena-Mendez et al., 2005).
Compared to humic acid, fulvic acid enables easier transfer of nutrients through plant root membranes, remains longer in saline soils, and tolerates a wider range of soil pH. That is why it is considered that fulvic acids affect the roots and humic acids affect the stem and aerial parts of plants.
Due to their molecular structure, humic substances provide numerous advantages in growing plants. It is considered that humic substances play a key role in the relationship between the soil and the plant in the way that they enable the transfer of nutrients, the exchange of carbon and oxygen between the plant and the soil, promote water retention, prevent water evaporation from the soil, and influence the development of microorganisms in the soil.
Today, various humic acid derivatives are used in agriculture, as well as humic substances in general. They are used to improve plant growth and resistance to abiotic stress, that is, increase the yield of cultivated crops.
Research has been conducted in which the positive effect of humic acid on the yield and quality of crops in sheltered areas and outdoors has been proven. According to Befrozfar et al. (2013) the yield of cucumbers was increased with foliar application of humic acid, while the oil yield per hectare of basil was increased with the use of humic acid by fertigation. According to Karakurt et al. (2009), the application of humic acid in organically grown peppers increased the total yield, early yield, average fruit weight, amount of soluble sugars, reducing sugars and chlorophyll b content. The use of fulvic acid in the cultivation of cucumbers increased the number of flowers per plant (Rauthan and Schnitzer, 1981), as well as the yield of corn in drought conditions.
In the FITOFERT range of fertilizers, in addition to biostimulants (Humiflex, Humistart, Humisuper Plus) , there are also HUMI - FULVI PRODUCTS:
FITOFERT FULVIMAX 80 is a preparation in the form of a water-soluble powder with a high content of fulvic acids. It is applied primarily in the early stages of the root system and its action affects the increased mobilization and uptake of phosphorus.
FITOFERT HUMIFLEX 24 is a more concentrated formulation of FITOFERT HUMIFLEX. It is used after the rooting phase, fertigation 10-20 l/ha or foliar 0.1-0.2%.
FITOFERT HUMIMAX 80 is formulated in the form of a water-soluble powder with a high concentration of humic acids. It is used after the rooting phase, during the growing season fertigation 3-10 kg / ha or foliar 0.05-0.1%.
Master Eng. Agriculture Bojana Stanković
Expert plant nutrition service of the Agromarket company