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Microbiological and bacterial fertilizers

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Microbiological and bacterial fertilizers are preparations containing highly active microorganisms that improve the nutritional conditions of crops.

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The level of potential and effective soil fertility 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 the action of which the processes of transformation of compounds containing nutrients are activated in the soil.

Preparations containing strains of nitrogen-fixing bacteria are widely used. The 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 source of nitrogen for the growing needs of agriculture. At the same time, the arguments are its harmlessness for humans and the environment at relatively low energy consumption for activation of nitrogen-fixing microorganisms.

According to field studies of Russian and foreign scientists, if agricultural crops cover 10-20% of their nitrogen demand by nitrogen fixation, application of inoculation will make a significant contribution into nitrogen balance.

Preparative forms of microbial fertilizers are: liquid, granular, gelatinous, and bulk.

Countries producing bacterial fertilizers and production volumes:

  • U.S. – 20 million ha/portion annually;
  • Canada – 2.5 million hectares/portion annually;
  • Austria – 6-9 million hectares/portion annually;
  • Brazil – 4-6 million hectares/portion annually;
  • India – 2-4 million hectares/portion annually;
  • Argentina – 2-3 million hectares/portion annually;
  • Uruguay – 1-2 million hectares/portion annually;
  • Russia – 0.3 mln ha/portion annually.

Seed pre-treatment with bacterial fertilizers can be carried out with or without adhesive. A 2.0% aqueous solution of sodium carboxymethylcellulose is used as an adhesive agent.

Bacterial fertilizers stored in dry rooms, protected from precipitation and direct sunlight, storage temperature 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 nutrition of plants.

Nitragin

Nitragin is a bacterial preparation containing active races of nodule bacteria, Bacterium radicicola, which live on the roots of legume crops and assimilate atmospheric nitrogen using the carbohydrates coming to the roots. Each legume crop corresponds to its specific nodule bacteria. Therefore, depending on the crop, the nitragin must contain specific, highly active and virulent strains of nodule bacteria

According to specificity, the following groups of bacteria are distinguished:

  • 1st for clover;
  • 2nd for pea, vetch, lentil, faba bean;
  • 3rd for alfalfa, melilot and fenugreek;
  • 4th for lupine, seradella;
  • 5th for soybeans;
  • 6th for beans;
  • 7th for mung bean;
  • 8th for peanuts and cowpea;
  • 9th for chickpea;
  • 10th for sainfoin.

Inoculation is inoculation of nodule bacteria to legume crops. It is carried out by treating seeds of leguminous plants with the preparation. During germination, nodule bacteria enter plant roots.

Rhizobacterin

Rhizobacterin and its advanced form Rhizobacterin-C is a preparation developed on the basis of associative diazotroph. The titer is 2-2.5 billion viable cells/ml. Promotes atmospheric nitrogen fixation, peroxyacetic acid biosynthesis, suppression of root pathogens. The form is liquid. Designed for pre-sowing treatment of grain crops (200 ml/ha) to increase yield, product quality and intensify the biological nitrogen fixation.

The preparation is based on nitrogen-fixing microorganisms (Klebsiella planticola 5) characterized by high colonizing ability, growth stimulation, antimicrobial action.

Atmospheric nitrogen assimilation allows reducing the recommended doses of nitrogen fertilizers for grain crops by 15-30 kg/ha. Yield increase averages 0.5-0.6 t/ha for barley, 0.6 t/ha for winter rye, 0.35-0.45 t/ha for spring and winter wheat.

Replacement of mineral nitrogen fertilizer with biological does not mean its productive use, because plant metabolism also depends on other nutrients, particularly phosphorus. With its lack of nitrogen is not included in the composition of proteins and nucleic acids, accumulates in the form of nitrites and nitrates, worsening the quality of production.

Rhizotorfin

Rhizotorfin contains nodule bacteria of the genus Rhizobium, which live on the roots of legume plants and provide symbiotic fixation of air nitrogen. It is used only under legume crops. Of the accumulated by these crops 100-300 kg of nitrogen per hectare per year, 1/3 is consumed by plants from soil, 2/3 is assimilated by nodule bacteria from the air.

There are 11 species of Rhizobium bacteria (according to L.M. Dorosinsky). Each species infects one or more species of legumes, so rhizotorfin is prepared for a particular legume.

It is produced in polyethylene bags; the weight of bacteria is calculated for one, two or five hectare portions.

Seeds are treated (inoculated) with the drug before sowing. Risotorfin increases the legume yield by 10-15%; in farms growing them for the first time it increases it by 50-100%.

Rhizotorfin is produced on the basis of sterilized peat. It is produced in a polyethylene packets packaged in the calculation of 1, 2 or 5 hectare portions with the indication under what culture this preparation is designed and what strain of bacteria. Shelf life – 6 months. Stored in a dark, dry room separately from pesticides at 3-15 °C. At subzero temperatures, as well as above 15°C, some of the nodule bacteria die, and overheating is more dangerous. If rhizotorfin has been subjected to freezing during transportation or storage, it should be kept at 13-15°C for 7-10 days.

Azotobacterin

Azotobacterin is a bacterial preparation containing a culture of Azotobacter chroococcum, a microorganism free-living in the soil with the ability to assimilate atmospheric nitrogen.

Azotobacter releases vitamins and growth substances, has fungistatic action, i.e. prevents the development of fungi, protecting plants from infection.

Azotobacterin is used in the cultivation of any crops. Two types of Azotobacterin are produced as fertilizers: humus-soil, or peat, and agar.

Phosphobacterin

Phosphobacterin is a preparation containing spore-bearing bacterium Bacillus megaterium var. phospaticum capable of mineralizing phosphorus of organic compounds.

It is available in dry and liquid form. Dry phosphobacterin contains bacterial spores mixed with kaolin. 250 g of powdered phosphobacterin is consumed per 1 ha.

Phytostimophos

Phytostimophos – phosphate-mobilizing microorganisms, live culture and growth-stimulating metabolites of Agrobacterium-radiobacter microorganisms. The drug titer is 6-10 billion viable cells per 1 ml. Growth-stimulating biopreparation performs microbial transformation of insoluble phosphates of soil and fertilizers into a plant-accessible form.

The product bacteria are able to colonize the roots of legume and nonlegume crops, forming associations. Phytostimophos is designed for microbiological phosphate-mobilization and yield increase of winter and spring cereals, corn, legumes and vegetable crops. The drug form is liquid. Consumption rate is 200 ml/ha.

The preparation increases mobility of hardly soluble phosphates of soil and fertilizers by 10-20%, decreases recommended doses of phosphate fertilizers by 15-30%, increases crop yield by 20% on average: increase of yield of fodder root crops – 10-25 t/ha, sugar beet – 9.0-9.5 t/ha, vegetable crops – 6-7 t/ha, legume crops – 0.25-0.35 t/ha.

Complex application of bacterial fertilizers

In a number of countries, joint inoculation of crop seeds with preparations of nitrogen-fixing and phosphate-mobilizing bacteria is successfully used. This allows to simultaneously improve nitrogen and phosphorus nutrition of plants and reduce the doses of mineral fertilizers.

Rizobacterin + Phytostimophos – synergistic binary preparations on the basis of diazotrophic and phosphate-mobilizing microbes. The form of the drug is liquid.

"Silicate" bacteria preparations

“Silicate” bacteria preparations are bacterial preparations based on the spore-forming culture, Bacillus mucilaginosus siliceus. Silicate bacteria can break down aluminosilicates, making soil potassium available to plants. The breakdown of aluminosilicates is caused by acids produced by the microorganisms. “Silicate” bacteria multiply well under conditions of adequate moisture, aeration, and a near-neutral environment. Acidic soils are not favorable for their life activity.

The preparation is used by treating the seeds. Dry spore and agar preparations are prepared as bacterial fertilizer.

Fungal fertilizers

Vesicular-arbuscular mycorrhiza

Vesicular-arbuscular mycorrhiza (VAM), ectomycorrhiza and endomycorrhiza are soil microflora that form symbiotic associations with higher plants. It improves plant growth in the absence of available phosphorus by improving phosphorus nutrition of plants. In symbiosis between the higher plant and fungi, the fungal mycorrhiza provides the plant with water and dissolved mineral salts, and the fungi use carbohydrates and organic compounds synthesized by the higher plant. The biological importance of mycorrhiza also lies in increasing the absorbing surface of the plant roots due to the mycelium of the fungus.

Endomycorrhizal fungi cultures have been isolated from natural and recultivated soils.

Vesicular-arbuscular mycorrhiza is an association in which Zygomycete fungi form arbuscules, hyphae, and vesicles in the root cells of higher plants.

Their positive effect on the yield of oats, barley, soybeans, and vetch and on the phosphorus supply to plants when grown on soil with a low content of mobile phosphorus has been proved. Mycorrhization of white clover seeds sown in grasses increases hay yield by 17% (control – 1.8 t/ha) and is equivalent to superphosphate effect at the rate of 90 kg/ha. At the same time, the proportion of clover in the composition of the herbage increased. Onion inoculation was noticeably evident on irrigated lands: the yield increased by 97%.

Joint inoculation of clover and other legumes with mycorrhiza and nodule bacteria is effective: the former contributes to phosphorus nutrition of plants, the latter to nitrogen nutrition. For example, in Wales, clover inoculated with mycorrhiza and nodule bacteria gave a yield with dry matter content 3 times higher, shoot formation increased 2-fold, and rhizobium nodule formation increased 5-fold.

Sources

Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al. – M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, 2017. – 854 с.

Fundamentals of agricultural production technology. Farming and crop production. Edited by V.S. Niklyaev. – Moscow: Bylina, 2000. – 555 с.

Plant growing/P.P. Vavilov, V.V. V., Gritsenko, V.S. Kuznetsov, et al; Edited by P.P. Vavilov. – M.: Agropromizdat, 1986. – 512 p.: ill. – (Textbook and textbooks for higher education institutions).