Influence of Albit on Soil Microbial Community: Increased Fertility and Healthier Soils

In contrast to most of analogues, Albit not only directly affects plants but also can indirectly stimulate plant growth, influencing soil microbial communities living on plant roots and in soil.

In comparison with other habitats, soil  has more diversity and abundance of microorganisms. More than one billion of live microorganisms are in gram of healthy fertile soil. It is a huge strength, which has the significant effect on growth and productivity of agricultural plants. It is only required to «direct» the development of soil microorganisms into «favorable direction» for agrosenosis. Microscopic fungi, some microalgae and a huge diversity of bacteria, such as of genera Bacillus, Pseudomonas, Klebsiella, Azotobacter, Beijerinckia, Clostridium, Arthrobacter, Flavobacterium, Aquaspirillum, Cellulomonas, Cytophaga, Mycobacterium, Derxia, Nocardia, Agromyces, Rhizobium, Agrobacterium and others refer to soil microorganisms. The majority of soil microorganisms positively affect plants (Lysak et al., 2003).

The richest biodiversity and largest number of microorganisms are typical for rhizosphere (the narrow area adjacent to plant roots). The most important factor determining the distinctions of rhizosphere and others parts of soil is the close interaction between microorganisms and plant. Plant activity determines to a great extent gaseous and water metabolism, as well as feed conditions inside of rhizosphere. In turn, soil microorganisms significantly positively affect plants: provide physiologically active compounds, vitamins, fixed nitrogen (nitrogen fixation), release phosphorous, potassium and microelements from soil minerals (Bab’eva, Zenova, 1989).

The majority of known soil bacteria are not free-living, but live in various types of interaction (association, symbiosis, and parasitism) with  plants, animals, and fungi. Interaction between bacteria plays the most important part in phyllosphere, rhizoplane, and rhizosphere. In soil community, bacterial species closely interact with each other and with variable environment.

Enrichment of soil by organic fertilizer can selectively guide the development of microbial consortiums towards the formation of new associations characterized by other functions (Fukui, 2003). This approach creates the background of microbiological control of plant pathogens. In the absence of external stress, natural bacterial consortium is a stabilizing factor preventing plant pathogens development within the soil. It is well-known that soil microorganisms can enhance or diminish fungicide effect. Suppressive soils are the soils which resist plant diseases (Singleton, Sainsbury, 1993).

Positive impact of Albit upon plants could be in part explained by indirect effect on soil community. Albit gets into soil mainly from the treated seeds and involve changes in operation of soil microflora including microorganisms in rhizosphere.

External influence of sufficient intensity causes microbial succession. Ecological succession is the systematic and well-organized process of change in the biodiversity and species structure of an microbiological community over time. From a practical point of view, it is important to guide microbial succession in the right direction —  toward the maximal stimulation of plant growth and suppression of pathogens. Investigations showed that Albit acts within the specified paradigm. Effect of Albit on soil microorganisms was studied at the Pedology Faculty of Moscow State University (the Department of Soil Biology and Agricultural Chemistry). Soil samples from the vegetation experiment pledged at the Department of Agricultural Chemistry in 1999 were studied.

It was found that treatment by Albit causes changes in the microbial community of plants’ rhizosphere, resulting in the reduction of pathogenic microscopic fungi number (e.g. Fusarium genus), and increasing of bacterial amount. Also the growth of micromycetes abundance (Gliocladium, Sladosporium and Trichoderma), antagonists of plant pathogens, was shown. After Albit treatment the number of Trichoderma and other soil fungi-antagonists increases. Thus, Albit application is an important factor of biostimulant activity together with plant immunization (Table 1, Fig.1).

The pot experiments were confirmed afield. According to the Ryazan and Saratov regional plant protection stations, systematical application of Albit improves the phytosanitary conditions of the soil. The experiments conducted in All-Russian Institute of Floriculture and Subtropical Crops demonstrated that Albit application the number of conidia of pathogen Phytophtora cactorum in garden soil was reduced by 52-56% (Fig. 2).

It was found out that Albit enhances total amount of microorganisms in soil and radical area, increase copiotrophs and nitrogen-fixing bacteria content in rhizosphere. Albit increased total amount of bacteria (from 3 to 3.5 õ 106 per g of soil, and from 8 to 14.7 õ 106 on roots of plants). However the amount of rhizospheric bacteria was reduced (Table 2). By the end of vegetation the differences in the number of distinct groups  of bacteria were smoothed out. It was noted for both kopiotrophic and oligotrophic bacteria. At the same time the reduction of total bacterial amount was shown for both the control, and, especially, the variant with Albit. It is connected with the fact that Albit application leads to significant stimulation of growth and launch of the soil microbial succession. As a result the number of bacteria initially increases, and then, at the final stages of succession, decreases as compared with the control.

At the same time, the number of growth-stimulating and nitrogen-fixing bacteria in soil increased under the influence of Albit (e.g., Azotobacter), growth-stimulating capacity of the soil increased by 50-100%, its overall toxicity significantly reduced: from 25-55 to 0-30 units (Table 3). Under the influence of Albit the increase in activity of beneficial microorganisms that encourage plant growth, and reduced activity of pathogenic microorganisms was established (Kostina, Zlotnikov, 2000).

Thus, reorganization of soil microbial community is an important mechanism that reduces the harmfulness of pathogens without inoculation of living biofungicides. Albit just stimulates the growth of fungicidal microorganisms, which are already present in the rhizosphere.

Albit does not contain living nitrogen-fixing bacteria. However, Albit enhances the potential activity of nitrogen fixation in rhizosphere at the beginning of the growing season by 12-66% due to the regulatory effect on the native microflora. It should be noted that this effect did not continue during all growing season, starting from the stage of stem elongation the level of nitrogen fixation decreased, but denitrification - increased (Fig. 3).

Fig. 3. The effect of Albit treatment on the activity of the nitrogen cycle processes in the rhizosphere of barley in a pot experiment (Department of Pedology, Moscow State University, 1999).
NFa - actual nitrogen fixation, NFp - potential nitrogen fixation, DNa - actual denitrification DNp - potential denitrification

Influence of Albit on soil N2-fixers was evaluated on the most active ones, Rhizobia. Indigenous soil population of Rhizobia is usually insufficient for formation of required amount of root nodules of legumes. Generally, additional treatment of seeds with Rhizobia inoculants is used to overcome this problem. Albit allows to use the alternative approach directly in the field: stimulation of activity and virulence of natural soil Rhizobial population. In field trial, performed by National Institute of Biological Plant Protection (Rus. Acad. Agric. Sci.) (Krasnodar, 2010) on soybean, it was shown, that Albit improves formation of root nodules on non-inoculated plants. In the field trial, application of Albit (seed treatment and spraying in combination with herbicides 30-50 mL/t) increased amount of nitrogen fixing nodules per one plant up to 13.5-53.2% over herbicide-only control.

Seed treatment with Albit increased the amount of nodules up to 39.7% over control, sprayings with Albit in combination with herbicide – up to 50.8%, combined application (seed treatment + spraying) – 53.2% (Fig. 4). Increased amount of nodules proportionally resulted in increased crop yield (up to 17 % over control).

Fig. 4. Influence of application rate of Albit and different ways of treatment, on the amount of nitrogen fixing nodules on soybean roots (field trial by National Institute of Biological Plant Protection, Krasnodar, 2010)

At the basis of the action of Albit on the soil microbial community, in our opinion, lies  the properties of poly-beta-hydroxybutyric acid (see details). This compound, like many polymers of biological origin (starch, cellulose, chitin) promotes initiation of microbial succession, formation of specific hydrolytic, and related organisms community, which has an indirect positive effect on plants. As a result, the Albit application provides an additional input of nitrogen and other nutrients in plants (see àor more details).

Chemicalization in agriculture using intensive technology destroys the natural microbiocenosis capable of protecting plants from phytopathogens. Pesticides inhibit microbial activity of the soil by 30-50% [Karpun, Janushevskaya, 2014]. In perennial field trials performed at National Scientific Research Institute of Floriculture and Subtropical Crops RAAS (Sochi) it was shown that Albit is able to reduce the negative impact of pesticides (based on dithianon, α-cypermethrin, λ-cyhalothrin, δ-methrin) on soil microbial consortium (Janushewskaya, Kaprun, 2011). Albit increases the resistance of soil microflora to the toxins, and normalizes its biological activity which is suppressed by the usage of pesticides (Fig. 5). Field trials were carried out on plantations of peach and apple trees (the farm gardens of All-Russian Scientific Research Institute of Floriculture and Subtropical Crops RAAS (Sochi)). Albit was used within standard protection protocol of gardens in conjunction with chemical pesticides (insecticides and fungicides). The first treatment of peach trees with Albit and dithianon was performed before flowering stage. Albit was used together with pyrethroids after flowering during the second and third treatments. Gardens without usage of pesticides, as well as virgin forest were taken as a control. During the field trials the dynamics of the overall biological activity of the soil all over the growing season was determined.

Fig. 5. The dynamics of potential activity of soil of apple garden after treatment with insecticide (a.i. is δ-methrin) in conjunction with Albit

The treatment of plot trials of apple garden with chemical pesticides decreased the basal respiratory activity of soil microflora (Fig. 4). Complete normalization of the respiratory activity of the soil was not observed even a month after application of pesticides. Albit used together with pesticides significantly reduced their negative side-effects: addition of Albit to standard chemical treatment almost regained the level of microbial activity on the level of undisturbed soil. These patterns were observed annually during the all studied period of 2008-2010 both with insecticides, and fungicides). The adaptogenic activity of Albit was especially expressed in drought conditions of 2009.

It was found that the intensity of the adaptogenic properties of Albit essentially depends on the soil conditions, which stimulate metabolic processes. The main non-specific mechanism of adaptogenic action of Albit is the activation of substrate-induced aerobic respiration, which laid in the base of increasing intracellular bioenergy resources and provide adaptation of microbial consortium to stress factors of different origins.

Albit is able to significantly reduce oil pollution of soil by stimulation the natural soil microflora and plant growth. The rate of oil decomposition in the soil increases in average by 1.67-3.15 times under the influence of Albit. Industrial tests showed that Albit together with sowing of oil-tolerant grasses reduces oil contamination of soils by 1.5-10.0 times during one growing season.

Thus, Albit exerts beneficial influence upon plants, increases their mineral nutrition, reduces the possibility of pathogens injury, reduces the toxicity of soils, acting indirectly through the soil microbial community. Albit acts as an integrated, balanced, and protective bio-stimulant, embracing nearly all spheres of plants vital activity.

Literature

1. Bab’eva I.P., Zenova G.M. Soil Biology. Moscow: MGU press, 1989.- 336 p. (rus)
2. Karpun N.N. The impact of pesticides on the ecological status of fruit agrocenoses. / N.N. Karpun, E.B. Janushesskaya // Plant Protection and Quarantine. - 2014. - ¹ 12. - P. 33-35.
3. Kostina N.V., Zlotnikov A.K. The influence of pesticide of microbial origin Albit on nitrogen fixation and denitrification activity of barley rhizosphere. // Abstracts of International Conference «Issues of Ecology and Physiology of microorganisms», 31 of November 1999, Moscow, Russia: «Dialog-MGU». – 2000. – P. 67.
4. Ly’sak L.V., Dobrovol’skaya T.G. Skvorcova I.N. Methods of bacterial soil diversity examination and soil microorganisms identification. – Ìoscow, Russia: «ÌÀÊS press», 2003. – 120 p. (rus)
5. Yanushevskaya E’.B., Karpun N.N. Role of Albit in the increase of soil microbial consortium pesticides resistance. // Plant Protection and Quarantine, 2011, ¹ 9:30-31. (rus)
6. Fukui R. Suppression of soilborne plant pathogens through community evolution of soil microorganisms // Microb. and Environ. – 2003. – V. 18. – ¹ 1. – P. 1-9.
7. Singleton P., Sainsbury D. Chromatography, Czapek-Dox medium, Melanin, Take-all, Suppressive soils, Rhizosphere, and Phenols // Dictionary of Microbiology and Molecular Biology. 2nd Ed. – 1993. –1019 p.
8. Pusenkova L. I. Change of specific composition of microbiota of rhizosphere and phyllosphere in sugar beet after treatments with biostimulants based on endophyte bacteria and their metabolites / L.I. Pusenkova, Å.Yu. Il'yasova, Î.V. Lastochkina, I.V. Maksimov, A.À. Leonova // Pochvovedenie. Biologiya pochv. (Soil Science. Biology of Soil). – 2016. – ¹ 10. – P. 1205–1213. (In Russian)

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