Organic Matter in Soil as a Source of Plant Growth Activators

It is well known that organic matter in soil is a significant source of mineral and carbon nutrition for plants. The organic part of the soil contains vast reserves of essential elements such as nitrogen and phosphorus, amounting to tons per hectare.

The amount of phosphorus-organic compounds in terms of P₂O₅ is about 0.5 in podzolic soils and approximately 1.5 t/ha in chernozems. All of this should be considered as a huge reserve of nutrients for plants, which gradually mineralizes and is slowly utilized by them. However, the role of organic matter in plant nutrition cannot be limited solely to the function of a reserve of mineral elements.

Biologically Active Substances in Soil

Based on numerous studies, it has been proven that soil contains organic substances that can participate in physiological and biochemical processes related to respiration, metabolism, and the absorption of mineral nutrients by plants, affecting their growth, development, and productivity. Among these organic compounds, the importance of growth activators should be noted.

The following should be included in this group of organic compounds:

• Vitamins
• Auxins
• Antibiotics
• Biological activators
• Humic acid and humates

Vitamins in Soil

The presence of a variety of vitamins in soils has been detected. These include aliphatic vitamins (e.g., pantothenic acid), aromatic vitamins (e.g., alpha-aminobenzoic acid), and various groups of heterocyclic vitamins (e.g., nicotinic acid, pyridine derivatives, thiamine, biotin, riboflavin, folic acid, etc.). The plow layer of soil on an area of 1 hectare contains several hundred grams to several kilograms of vitamins.

Auxins and Antibiotics

The group of biologically active soil substances includes auxins, which enhance growth processes and root system development. Heteroauxin (beta-indolylacetic acid), used in horticulture and vegetable growing for rooting cuttings and seedlings and for accelerating fruit ripening, is formed in the soil as a product of the activity of various soil microorganisms.

The soil contains organic substances produced by microorganisms that possess antibiotic properties (streptomycin, penicillin, terramycin, etc.), which affect the composition of soil microbial communities and, upon entering plants, retain their properties for a long time, potentially protecting them from diseases.

Physiological Significance of Humic Substances

Many studies on the physiological significance for plants of the group of humic substances themselves are of great interest. Humic substances, extracted from peat, fossil coals, and soils in the form of highly dispersed colloids and true solutions, stimulate the growth of higher plants in small doses.

Humic substances activate root growth and development in plants, especially during their early growth stages, and also affect the physicochemical state of plant protoplasm. It has been noted that in the presence of humic substances, the permeability of plant cells increases, facilitating the enhanced uptake of water and nutrients by plants.

Application of Microfertilizers and Potassium Humate

The application of microfertilizers together with mineral fertilizers in rows and pockets or with organic matter in the form of composts significantly increases their effectiveness. Mineral fertilizers, when absorbed by microfertilizer particles, are better utilized by plants, contributing to the targeted improvement of nutrition for various agricultural crops.

The nature of potassium humate action has long been studied by us in various regions of Ukraine. First and foremost, it was established that potassium humate has significant adsorption capacity and positively affects the activity of soil microflora, as well as the microflora of manure during composting.