Humates

Humates, or fertilizers based on humic acids, are a group of natural, high-molecular-weight plant growth regulators; they are compounds based on humic acids. They are non-toxic, non-carcinogenic, do not cause mutations, and do not possess embryological activity. Residual amounts of humates in plants are not detected, since they are easily and rapidly incorporated into plant metabolism.

When humic acids are used as plant growth regulators, the physiological activity is exhibited not by the humic acids themselves but by their salts of monovalent alkali metals (sodium and potassium) and ammonium. This is because humic acids are insoluble in water and therefore are not absorbed by plants, whereas salts of monovalent alkali metals and ammonium are highly soluble in water and available to plants.

Humic acids have a multifaceted effect: they activate bioenergetic processes, stimulate metabolism and synthetic processes, improve the penetration of nutrients through the plasmalemma, enhance enzymatic systems, and increase the adaptive properties of the plant organism. Depending on external conditions, they may differ in stability and activity, owing to which they can be used both as fertilizer and as plant growth stimulants.

The reason for the physiological activity of humic acids is considered to be their effect on the bioenergetic system of the plant organism (Khristeva L. A., 1973). An increase in the organism's energy reserves promotes protein synthesis, thereby increasing plant resistance under extreme conditions and photosynthetic capacity.

The ability of humic acids to form complexes and their sorption activity make it possible to use them to bind heavy metals into insoluble compounds in contaminated soils.

Humic acids interact differently with metal cations: calcium ions form salt-like calcium humates, in which the ionic form of carboxyl groups is observed. The zinc ion replaces the hydrogen of carboxyl groups. Copper replaces the hydrogen of both carboxyl and phenolic groups. In all cases, humic acids are reprecipitated in the form of insoluble or poorly soluble metal salts or complexes.

Humates participate in soil structure formation: on light soils, aggregation occurs; on heavy soils, they prevent the formation of crusts and cracks, and aeration, water-retention capacity, and water permeability are improved.

The use of humates in agriculture promotes:

• an increase in the yield of cereals, vegetables, and fodder crops;
• an increase in seed germination and germination energy;
• enhanced root formation and metabolism in plants, uptake of mineral nutrients, and increased plant resistance to diseases, frost, and drought.

Sodium, potassium, and ammonium humates are used. Sodium and potassium humates are obtained by saturation with potassium or sodium hydroxides. Ammonium humate is obtained by treating raw material with an ammonia solution.

For irrigation, a 5% humate solution diluted at a ratio of 1:1000 is used; for seed treatment, 1:500; for treating tubers and seeds of cereal crops, 1:250. Spraying plants during the growing season is carried out 2–4 times.

To solutions of humic acid salts, trace elements, organic acids, biologically active substances, amino acids, and vitamins can be added; these are used by germinating seeds, plants, and soil-dwelling microorganisms. More than 60 preparations are produced, united in the group “Fertilizers based on humic acids.”

The different chemical composition of the preparations broadens the spectrum of their application. They can be used for pre-sowing seed treatment and for spraying vegetating plants. Production trials of these preparations under various soil and climatic conditions have shown their positive effect on the yield of all agricultural crops. Vegetables, fruit crops, and fodder crops proved to be the most responsive. It is advisable to combine the use of fertilizers based on humic acids with pre-sowing seed preparation and spraying of crops with plant protection products. Combined use with pesticides also has the advantage that they relieve the stress effect exerted by pesticides on cultivated plants.