Industrial humic preparations: production technology and properties
Today all around the globe humate-based fertilizers are in an increasingly greater demand. This can be explained by the fact that we have now ever more research data testifying to the positive effect humic substances have upon growth and development of plants and upon the quality of food products and soil fertility. Humic compounds are physiologically active substances that contribute to regulation and intensification of metabolic processes in plants and in soil. It has been established that humic substances not only increase production and fruit size and shorten ripening time, but also improve product quality by raising protein/sugar/amino-acid/vitamin content, and at the same time by reducing concentration of nitrates.
In 1981 a decision was taken to set up the International Humic Substances Society (IHSS) whose first president was R.L. Malcolm, USA. Since 1983 international IHSS conferences have been organized where precedence of Soviet scientists (above all Ms.L.A.Khristeva and Ms.S.S. Dragunova) was confirmed in the research aimed at the development of humic fertilizer production technologies. Yet, humic industrial technology boom started in Europe and other countries of the world in 1980-1990-ies. In Russia the active production of industrial humic preparations only began in late 1990-ies. Nonetheless, technological level of Russian industry ensured a product quality that was highly competitive with best Western developments available. This was the reason why Russian market despite its considerable size, does not know imported industrial humates till the present day.
Humates are a group of natural high-molecular organic compounds that due to their structure and physical-chemical characteristics are very active from a physiological point of view. Their MoA (mechanism of action) implies stimulation of all bio-chemical processes in a plant both during seed germination and root formation and later during the whole cycle of plant growth and development. Humates alter cell membrane permeability, boost ferment activity, increase chlorophyll content and photosynthesis productivity, stimulate tissue respiration and synthesis of proteins, sugars, amino acids and vitamins. At the same time humates are non-toxic, non-carcinogen and non-mutagen compounds, which in its turn creates a basis for production of environmentally sound food.
Also humates have a considerable effect upon hydro-physical and hydro-chemical properties of soil, i.e.:
- they increase water capacity of light soils (by 30% in the average), by this contributing to the creation of agronomically valuable crumby/granular structures;
- they improve void content and water permeability of heavy soils by this preventing cracks, crusts, ploughing layer hardening and creation of tillage pan;
- they help soil aeration and increase air permeability of the soil profile, optimize both root respiration and general redox properties of soil;
- they regulate ionic exchange reactions between the soil and water solutions;
- they change soil buffer capacity thus helping to maintain a natural pH-level even if excessive amounts of acidic or alkaline agents are entering the soil.
In its turn, changes in the humus content of soils contribute to the development of soil germs directly involved in desorption of nutrients, i.e.: nitrogen-fixing, cellulose-fermenting and butyrate-producing bacteria, along with ammonifiers and other germs that play a vital role in the nutrition and growth of plants. At the same time they also boost the fermentative activity of soil that contributes to the lability of nutrients. The activity of such ferment as follow is improved: urease, phosphatase, catalase, dehydrogenase, esterase, et alia. As a result of their action, hard-to-absorb mineral compounds of phosphorus, potassium, calcium, magnesium are turned into forms that are easily consumable by plants. Thus, by applying humates into the soil we have in the ploughing layer an increase of labile phosphorus by 1,5-2 times, and an increase of exchangeable potassium and consumable nitrogen by 2 – 2,5 times. In what concerns micro-elements, they form labile chelate compounds with humic substances that enter plants easily; research shows that iron and manganese can be consumed by plants only as humates of these two metals.
An important factor is the way humates inter-react with various ecotoxicants who enter the soil as dust, ashes, with rain or within mineral fertilizers. What takes place here is irreversible binding of heavy metals and radio nuclides into insoluble non-labile complex compounds that are then taken away from the circulation of elements of the soil, which prevents their finding their way into the food we eat. In addiction to this, the fact that soil microflora is intensified by humates also helps to faster degrade toxic organic compounds. At the same time organic ecotoxicants like pesticides, hydrocarbons, phenols, aldehydes, etc., are effectively adsorbed by humates, which reduces their toxicity for plants and humans.
It has been observed that application of humates in agriculture:
• increases production of crops, feed crops and vegetables by 10 – 30 % at the average;
• seed germinating capacity is improved and germination increased;
• plant metabolism is improved, consumption of minerals increased along with root system formation;
• seedling establishment after re-planting is improved;
• plant resistance against diseases, frosts and droughts is increased due to a more active nitrate reductase;
• nitrate, pesticide, heavy metal ion and radionuclide content is decreased, which allows us to claim that humates can be used for soil recultivation and decontamination.
Usually humates are used for seed pre-treatmen and for root or foliar dressings. Seed pre-treatment can be combined with subsequent foliar dressings or waterings. Humate application can be also combined with plants/seed treatments by pesticides. Consumption rate of the products – 30 to 100 g of dry substance per 1 hectare (subject to product type and crop species).
Today industrial humates are widely used in both Americas, in China and Australia, in African counties and in Central Europe, and, of course, in Russia. Having said that we should mention that actually in use are the following three main types of humates: sodium humate, potassium humate and ammonium humate. Most widespread are the first two ones. It also often happens that preparations containing both forms of humic salts are applied.
So far, the main raw materials for humic substance production have been turf or special sorts of brown coals. The main advantage of this raw stock is that it is available in various regions of the world. Humic acids contained in such raw products are high molecular insoluble fractions. Extraction of humic acids is done by monovalent cations of sodium, potassium or ammonium. This process results in dilutions of humic salts, to be further subjected to evaporation till their concentration reaches 2-8%. This method defines both good product properties and its high price per active substance content. Yet, such preparations can be easily dissolved and have successfully found their gap in the market. More promising economically is the so-called "dry processing of brown coals" technology with dry humates at the output. It is very cheap and is used by most major producers in different countries. At the same time, its final products have their shortcomings among which we can mention:
• partial solubility and a high content of insoluble ballast components;
• difficulties linked to ensuring a stable composition of the product, including heavy metal content, which are caused by variances in the composition of raw stock in deposits;
• small amount or no fulvic low-molecular acids.
Nonetheless, due to their low price, such humic preparations are most popular both in the international and Russian markets.
In 1980-ies Leningrad scientists developed new revolutionizing technologies of the production of ecologically friendly high concentration humic salts. One of the features of this technology is that it imitates the natural processes of humification of virtually any lignin-containing organic matter, which usually does not contain humic compounds. In nature this process of humification of wood lignin can carry on for ages, while the developed technology can shorten this time down to 1 or 2 hours. By this, the production of a wide range of high- and low-molecular humic compounds is ensured, including fulvic salts. Extensive research and production technology efforts made since 1999 has led to the development and marketing of a new generation humic preparation called Lignohumate®.