Microbiological and bacterial fertilizers
Microbiological and bacterial fertilizers — preparations containing highly active microorganisms that improve the nutrient conditions of agricultural crops.
The level of potential and effective fertility of soil is determined by the intensity and direction of microbiological processes, which are regulated by the number of microorganisms.
Microbiological and bacterial preparations contain specific strains of microorganisms, under whose action transformation processes of compounds containing nutrients are activated in the soil.
Preparations containing strains of nitrogen-fixing bacteria have become widespread. Interest in the microbiological fixation of atmospheric nitrogen is due to the role of this process in the nitrogen balance and its prospects as a nitrogen source for meeting the growing needs of agriculture. At the same time, the arguments are its harmlessness to humans and the environment with relatively low energy costs for activating nitrogen-fixing microorganisms.
According to field studies by domestic and foreign scientists, if agricultural crops cover 10–20% of their nitrogen requirement through nitrogen fixation, then inoculation will make a significant contribution to the nitrogen balance.
Preparative forms of microbial fertilizers are: liquid, granulated, gel-like, free-flowing.
Countries producing bacterial fertilizers and production volumes:
- USA — 20 million ha/portions annually;
- Canada — 2.5 million ha/portions annually;
- Austria — 6–9 million ha/portions annually;
- Brazil — 4–6 million ha/portions annually;
- India — 2–4 million ha/portions annually;
- Argentina — 2–3 million ha/portions annually;
- Uruguay — 1–2 million ha/portions annually;
- Russia — 0.3 million ha/portions annually.
Presowing treatment of seeds with bacterial fertilizers can be carried out with or without an adhesive. A 2.0% aqueous NaCMC solution is used as an adhesive.
Bacterial fertilizers are stored in dry rooms protected from precipitation and direct sunlight; storage temperature is from 0 to +4°C. Shelf life depends on the type and form of bacterial fertilizers.
In world practice, attention is paid to the role of soil biota in improving phosphorus plant nutrition.
Nitragin
Nitragin is a bacterial preparation containing active races of nodule bacteria — Bacterium radicicola, which live on the roots of leguminous crops and assimilate atmospheric nitrogen, using carbohydrates supplied to the roots. Each leguminous crop corresponds to specific nodule bacteria. Therefore, depending on the crop, Nitragin must contain specific, highly active, and virulent strains of nodule bacteria.
By specificity, groups of bacteria are distinguished: 1st — for clover; 2nd — for pea, vetch, chickling vetch, lentil, faba beans; 3rd — for alfalfa, sweet clover and fenugreek; 4th — for lupine, serradella; 5th — for soybean; 6th — for bean; 7th — for mung bean; 8th — for peanut and cow pea; 9th — for chickpea; 10th — for sainfoin.
Inoculation is the introduction of nodule bacteria to leguminous crops. It is carried out by treating the seeds of leguminous plants with the preparation. During germination, nodule bacteria enter the roots of plants.
Rizobacterin
Rizobacterin and its improved form Rizobacterin-S are a preparation developed on the basis of an associative diazotroph. Titer — 2–2.5 billion viable cells/ml. It promotes fixation of atmospheric nitrogen, biosynthesis of peroxyacetic acid, and suppression of root pathogens. Form — liquid. It is intended for presowing treatment of seeds of cereal crops (200 ml/ha) to increase yield, product quality, and intensify biological nitrogen fixation.
The preparation is based on nitrogen-fixing microorganisms (Raoultella planticola, formerly Klebsiella planticola 5), characterized by high colonizing ability, growth stimulation, and antimicrobial action.
Assimilation of atmospheric nitrogen makes it possible to reduce recommended doses of nitrogen fertilizers for cereal crops by 15–30 kg/ha. The average yield increase is: barley — 5–6 c/ha, winter rye — 6 c/ha, spring and winter wheat — 3.5–4.5 c/ha.
Replacement of mineral nitrogen fertilizer with biological nitrogen does not mean its efficient use, since plant metabolism also depends on other nutrients, in particular phosphorus. When it is deficient, nitrogen is not incorporated into proteins and nucleic acids and accumulates in the form of nitrites and nitrates, worsening product quality.
Rhizotorfin
Rhizotorfin contains nodule bacteria of the genus Rhizobium sp., which live on the roots of leguminous plants and provide symbiotic fixation of atmospheric nitrogen. It is used only for leguminous crops. Of the 100–300 kg of nitrogen per 1 ha per year accumulated by these crops, 1/3 is consumed by plants from the soil, and 2/3 is assimilated by nodule bacteria from the air.
There are 11 known species of Rhizobium bacteria (according to L. M. Dorosinsky). Each species infects one or several species of leguminous crops, so Rhizotorfin is prepared for a specific leguminous crop.
It is produced in polyethylene bags; the mass of bacteria is calculated for one, two, or five hectare portions.
Seeds are treated (inoculated) with the preparation before sowing. Rhizotorfin increases the yield of legumes by 10–15%; on farms growing them for the first time, by 50–100%.
Rhizotorfin is produced on the basis of sterilized peat. It is produced in polyethylene bags packaged for 1, 2, or 5 hectare portions, indicating the crop for which the preparation is intended and the bacterial strain. Shelf life — 6 months. It is stored in a dark, dry room separately from pesticides at a temperature of 3–15°C. At negative temperatures, as well as above 15°C, some nodule bacteria die, and overheating is more dangerous. If during transport or storage Rhizotorfin was frozen, it is kept at 13–15°C for 7–10 days.
Azotobacterin
Azotobacterin is a bacterial preparation containing a culture of azotobacter — Azotobacter chroococcum — a microorganism free-living in soil with the ability to assimilate atmospheric nitrogen.
Azotobacterin releases vitamins and growth substances and has a fungistatic effect, i.e., it prevents the development of fungi, protecting plants from infection.
Azotobacterin is used in the cultivation of any agricultural crops. Two types of Azotobacterin are manufactured as fertilizers: humus-soil, or peat, and agar.
Phosphobacterin
Phosphobacterin is a preparation containing the spore-forming bacterium Bacillus megaterium var. phospaticum, capable of mineralizing phosphorus from organic compounds.
It is produced in dry and liquid forms. Dry Phosphobacterin contains bacterial spores mixed with kaolin. 250 g of powdered Phosphobacterin is used per 1 ha.
Phytostimophos
Phytostimophos — phosphate-mobilizing microorganisms, a live culture and growth-stimulating metabolites of microorganisms Agrobacterium radiobacter (syn. Rhizobium radiobacter). Titer of the preparation — 6–10 billion viable cells per 1 ml. A growth-stimulating biopreparation, it carries out microbiological transformation of insoluble soil and fertilizer phosphates into a plant-available form.
The bacteria of the preparation are able to colonize the roots of leguminous and non-leguminous crops, forming associations. Phytostimophos is intended for microbiological phosphate mobilization and increasing the yield of winter and spring cereal crops, maize, grain legumes, and vegetable crops. Form of the preparation — liquid. Application rate — 200 ml/ha.
The preparation increases the mobility of sparingly soluble soil and fertilizer phosphates by 10–20%, allows reducing recommended doses of phosphorus fertilizers by 15–30%, and increases yield on average by 20%: yield increase of fodder root crops — 10–25 t/ha, sugar beet — 9.0–9.5 t/ha, vegetable crops — 6–7 t/ha, grain legumes — 0.25–0.35 t/ha.
Combined use of bacterial fertilizers
In several countries, combined inoculation of crop seeds with preparations of nitrogen-fixing and phosphate-mobilizing bacteria is successfully used. This makes it possible to simultaneously improve nitrogen and phosphorus nutrition of plants and reduce doses of mineral fertilizers.
Rizobacterin + Phytostimophos — synergistic binary preparations based on diazotrophic and phosphate-mobilizing introduced microbes. Form of the preparation — liquid.
Preparations of “silicate” bacteria
Preparations of “silicate” bacteria — a bacterial preparation based on a spore-forming culture — Bacillus mucilaginosus sp. siliceus. Silicate bacteria are able to destroy aluminosilicates, making soil potassium available to plants. Destruction of aluminosilicates occurs under the action of acids secreted by microorganisms. “Silicate” bacteria reproduce well under conditions of sufficient moisture, aeration, and a near-neutral medium reaction. Acidic soils are unfavorable for their vital activity.
The preparation is used by treating seeds. As a bacterial fertilizer, dry spore and agar preparations are made.
Fungal fertilizers
Vesicular-arbuscular mycorrhiza (VAM)
Vesicular-arbuscular mycorrhiza (VAM), ectomycorrhiza, and endomycorrhiza are soil microflora forming symbiotic associations with higher plants. It improves plant growth under deficiency of available phosphorus by improving phosphorus nutrition of plants. In symbiosis of a higher plant with fungi, the fungal mycorrhiza provides the plant with water and dissolved mineral salts; the fungi use carbohydrates and organic compounds synthesized by the higher plant. The biological significance of mycorrhiza also lies in increasing the absorbing surface of plant roots due to the fungal mycelium.
Cultures of endomycorrhizal fungi have been isolated from natural and reclaimed soils.
Vesicular-arbuscular mycorrhiza is an association in which Zygomycete fungi form arbuscules, hyphae, and vesicles in the root cells of the higher plant.
Their positive effect on the yield of oats, barley, soybean, vetch and phosphorus uptake by plants when grown on soil with low available phosphorus has been proven. Mycorrhization of white clover seeds sown in a grass stand increases hay yield by 17% (control — 17.8 c/ha) and was equivalent to the effect of superphosphate at 90 kg/ha. At the same time, the proportion of clover in the grass stand increased. Inoculation of onion was noticeably manifested on irrigated lands: yield increased by 97%.
Combined inoculation of clover and other legumes with mycorrhiza and nodule bacteria is effective: the former promotes phosphorus nutrition of plants, the latter nitrogen nutrition. Thus, in Wales, clover inoculated with mycorrhiza and nodule bacteria gave a yield with dry matter content 3 times higher; shoot formation increased 2-fold; rhizobium nodule formation increased 5-fold.
References
1. Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Ed. by Mineev V. G. Moscow: Publishing House of VNIIA named after D. N. Pryanishnikov.
2. Niklyaev V. S. (2000). Fundamentals of Agricultural Production Technology. Agriculture and Crop Production. Moscow: “Bylina”.
3. Vavilov P. P., Gritsenko V. V., Kuznetsov V. S. et al. (1986). Crop Production. Ed. by Vavilov P. P. 5th ed., revised and enlarged. Moscow: Agropromizdat.
