CC BY
1UDK. 631.461
MICROBIOLOGICAL MONITORING OF COTTON FIELD SOILS IN THE JIZZAKH
REGION
*Zakiryaeva S.I, 2Karimova Sh.Sh., 3Kutlieva G.Dj
1,2,3The Institute of Microbiology, Academy of Sciences of the Republic of Uzbekistan
1 szakiryaeva@gmail .com https://doi.org/10.5281/zenodo.10935404
Abstract. Microbiological soil monitoring was conducted across 12 cotton fields in the Jizzakh region. The findings revealed notable deviations from normal levels in key microbial populations. Ammonifying bacteria, phosphorus-mobilizing bacteria, and oligonitrophilic microorganisms, all belonging to the primary physiological group, exhibited a decrease of 1 to 2 orders in comparison to standard levels. Actinomyceteswere notably reduced by 2 to 3 orders, falling three orders below the established norm. Furthermore, free-living nitrogen-fixing bacteria were entirely absent in all examined soil samples.A critical observation was made regarding micromycetes, with some soil samples showing a significant increase of 1 order above the norm. The identified micromycetes belonged to the genera Mucor, Aspergillus, Penicillium, Alternaria, Rhizopus, and Fusarium. These findings underscore the need for further investigation and remediation measures to restore the microbial balance essential for soil health and sustainable agricultural practices in the region.
Keywords: soil, microbiological monitoring, ammonifying bacteria, phosphorus-mobilizing bacteria, oligonitrophilic microorganisms, actinomycetes, micromycetes.
Аннотация. Жиззах вилоятининг 12 та пахта экин майдонлари тупроцлари микробиологик мониторинг цилинди. Олиб борилган мониторинг натижасида, барча намуналарда асосий физиологик гуру% микроорганизмларидан аммонификатор бактериялари, фосфор парчаловчи бактериялар ва олигонитрофил микроорганизмлари мицдори нормадан 1 ва 2 тартибга, актиномицетлар эса 2-3 тартибга кам эканлиги, эркин %олда яшовчи азот фиксация цилувчи бактериялар барча мониторинг цилинган намуналарда умуман учрамаганлиги кузатилди. Микромицетларнинг мицдори айрим намуналарда нормадан 1 тартибга куп эканлиги, %амда ушбу микромицетлар Mucor, Aspergillus, Penicillium, Alternaria, Rhizopus ва Fusarium авлодларига мансуб эканликлари аницланди.Ушбу тадцицот натижалари минтацада тупроц саломатлиги ва барцарор цишлоц хужалиги амалиёти учун зарур булган микробиал мувозанатни тиклаш учун цушимча та^лиллар ва ремедиация чора тадбирлари зарурлигини таъкидлайди.
Калит сузлар: тупроц, микробиологик мониторинг, аммонификатор бактериялар, фосфор парчаловчи бактериялар, олигонитрофил микроорганизмлар, актиномицетлар, микромицетлар.
Аннотация. Проведен микробиологический мониторинг почв 12 хлопковых полей Джизакской области. В результате мониторинга отмечено, что количество аммонифицирующих бактерий, фосформобилизующих бактерий и олигонитрофильных микроорганизмов из основной физиологической группы микроорганизмов во всех пробах было на 1 и 2 порядка, а актиномицеты - на 2-3 порядка ниже нормы. Свободноживущие азотфиксирующие бактерии во всех изученных образцах почв не обнаружены. Установлено, что количество микромицетов в некоторых образах почв на 1 порядок превышает норму и эти микромицеты относятся к родам Mucor, Aspergillus, Penicillium, Alternaria, Rhizopus и Fusarium. Эти результаты исследований подчеркивают
необходимость дальнейших исследований и мер по восстановлению микробного баланса, необходимого для здоровья почвы и устойчивых методов ведения сельского хозяйства в регионе .
Ключевые слова: почва, микробиологический мониторинг, аммонифицирующие бактерии, фосформобилизующие бактерии, олигонитрофильные микроорганизмы, актиномицеты, микромицеты.
Microorganisms are key components of soil biodiversity, encompassing both free-living and non-free-living soil biota, which contribute significantly to thriving plant life. These microbial communities provide valuable information about fundamental ecological processes. Being ubiquitous in a variety of habitats, microorganisms act as first responders to chemical and physical changes in the soil. Shifts in microbial communities, given their integral role in soil formation processes, serve as indicators of changes in the functional structure of the corresponding ecosystems [1].
Plants, as hosts to a wide range of microorganisms, including bacteria, archaea, fungi, viruses and oomycetes, represent a complex network of interactions between flora and microorganisms [2]. The symbiotic relationship between microorganisms and plants highlights their vital role in ecosystem functioning, emphasizing the uniqueness of each ecosystem based on its distinct microbial composition. This has stimulated deep interest in the study of microorganisms, opening up an understanding of how their functions can be modulated to improve overall quality [3].
This study used soil samples collected from 12 cotton fields (M. Ulugbek, Zarafshon, A. Navoi, Kupisor, Uchtepa, Samarkand kuduk, Kh. Nosirov, Mekhnatabad, U. Khatamov, Kh. Olimjon, Z. M. Babur, Yangi Hayot) in Jizzakh region. The complex relationship between microorganisms and soil formation directly affects fertility. Organic matter, consisting mainly of plant roots, contributes to the formation of humus through decomposition. Microorganisms, especially bacteria, actinomycetes and fungi, play an indispensable role in the breakdown of complex organic compounds into simpler forms.
Given the critical importance of soil microflora to ecosystem health, there is an urgent need to comprehensively understand and improve both the quantity and quality of microorganisms. This necessitates a scientific approach to the process of improving soil microbiota. Therefore, the primary goal of our research is to conduct microbiological monitoring and study of soil in cotton fields, which will contribute to a broader understanding of soil health and the promotion of sustainable agricultural practices.
For a comprehensive microbiological analysis of soil samples, generally accepted methods of soil microbiology were used [4]. Sampling depth ranged from 0 to 30 cm to assess the abundance of primary physiological groups in the soil. Various nutrient media were used to cultivate specific microorganisms present in the soils examined. In particular, ammonifying bacteria were cultured on the PA nutrient medium, phosphorus-degrading bacteria on the Pikovsky nutrient medium, oligonitrophils on the Ashby nutrient medium, and actinomycetes and micromycetes on the solid Czapek nutrient medium.
For microbiological analysis, a suspension was prepared from a soil sample. Ten grams of soil sample was mixed with 90 ml of sterilized water, shaken vigorously for 5 minutes, then 1 ml of the resulting suspension was pipetted and placed in a sterilized test tube containing 9 ml of water. This procedure was repeated serially, with serial dilutions reaching 1:1,000,000, and the
procedure was repeated three times. Then one milliliter of liquid from the test tube was inoculated in triplicate onto special solid selective culture media in Petri dishes.
Each selective nutrient medium corresponds to specific microorganisms: PA (meat peptone) for ammonifiers, Pikovsky for phosphorus-degrading bacteria, Ashby for oligonitrophils and nitrogen fixers, Chapek for micromycetes and actinomycetes. The inoculated Petri dishes were then examined using the dilution method, which enabled a detailed and accurate assessment of the microbial content of the soil samples. This careful approach ensures the reliability and accuracy of the microbiological analysis and provides valuable information about the composition and dynamics of soil microorganisms in the study areas.
The breakdown of proteins by ammoniacal bacteria results in the release of nitrogen in the form of ammonia, a process that is crucial for plant nutrition.
As a result of microbiological monitoring, the amount of ammonifying bacteria in soil samples taken from 12 cotton fields was found to be 106 to 107CFU cells per 1 gram of soil. The amount of ammonifying bacteria in the soils of M. Ulugbek, Zarafshon, Uchtepa, Samarkand kuduk, Mekhnatabad, U. Khatamov and Kh. Olimjon cotton fields is 2.1-9x106CFU/g on average, and their amount is on average 2.5-8.2x107CFU/g in the remaining samples formed.
Phosphorus is the most limiting nutrient for plants. Despite the abundance of phosphorus in the soil, it is not in a form suitable for absorption by plants. Plants can only take mono- and dibasic phosphates in soluble form. Phosphate-degrading bacteria are responsible for the dissolution of phosphates from tricalcium phosphate and complex phosphate compounds.
In the monitored soil samples, it was found that the amount of phosphorus-decomposing bacteria was in the same order in the soil of 11 cotton fields, and it was 3-9x105CFU/g on average in 1 gram of soil. It was observed that phosphorus-decomposing bacteria were not found in the soils of 1 cotton-planted area (Yangi Khayot).
Oligonitrophils are very important in the transformation of nitrogen and carbon in the soil. This group of microorganisms breaks down the carbon part of the most important organic matter.
In the process of microbiological monitoring, the amount of oligonitrophilic microorganisms in these soil samples was found to be 105 to 106CFU cells per 1 gram of soil. The amount of oligonitrophilic microorganisms in the soil of Uchtepa and Z.M. Babur cotton fields was on average 5.2-5.7x105CFU/g, and in the rest of the cotton fields, it was one order higher, on average 1.1-1.7x106CFU/g.
Nitrogen-fixing bacteria have the ability to absorb nitrogen from the atmosphere. Their accumulation in the soil can cause it to be enriched with a certain amount of nitrogen. However, free-living nitrogen-fixing bacteria were not found in all studied soil samples.
Actinomycetes are among the most common microorganisms in the soil. Actinomycetes absorb organic and mineral forms of nitrogen, are able to break down mono-, di- and polysaccharides, as well as animal and vegetable oils. Some actinomycetes are able to decompose soil humus and chitin. Actinomycetes are resistant to high concentrations of salts, some of them are able to accumulate nitrogen in the atmosphere. As a result of microbiological monitoring, it was found that the amount of actinomycetes in the soil of cotton fields is 103 to 104CFU cells per 1 gram of soil.
Along with other microorganisms in the soil, soil microscopic fungi play an important role in soil fertility. A large number of their species actively participate in the decomposition of plant residues in the soil. The amount of microscopic fungi depends on the degree of cultivation of the soil, its season.
The amount of micromycetes in the studied soil samples was found to be 103 to 104 CFU cells per 1 gram of soil. The average amount of micromycetes was 1.5-3x104 CFU/g in Zarafshon, A. Navoi, Kupisor, Uchtepa, Kh. Nosirov, Kh. Olimjon, Z.M. Babur and Yangi Khayot cotton fields. In the rest of the samples, their amount was found to be one order less (1.5-4.5x103 CFU/g) (Fig. 1).
12 8
5
4 | M
3 r —
0 3 6 9 12 15 18 21 24 27 30
Ig CFU/g soil
■ AMB "PMB ■ OM «ACM »MM
Figure 1. The amount of the main physiological group of microorganisms in the soil from 12 cotton fields of Jizzakh region, lg CFU/g of soil
1-M.Ulugbek, 2-Zarafshon, 3-A.Navoi, 4-Kupisor, 5-Samarkand kuduk, 6-Uchtepa, 7-Kh. Nosirov, 8-Mekhnatabad, 9-U.Khatamov, lO-Kh.Olimjon , 11-Z.M.Babur, 12-Yangi Hayot.
AMB-ammonifying bacteria; PMB-phosphorus-mobilizing bacteria; OM-oligonitrophilic microorganisms; ACM-actinomycetes; MM-micromycetes.
Microbiological monitoring of soil in 12 cotton fields in the Jizzakh region revealed notable imbalances in microbial composition. The amounts of ammoniacal bacteria, phosphorus-degrading bacteria and oligonitrophilic microorganisms, integral components of the primary physiological group, were consistently 1 to 2 orders below than the norm. Furthermore, free-living nitrogen-fixing bacteria were completely absent in all monitored samples.
Significantly, the presence of micromycetes in some samples exceeded the norm by an order and these micromycetes, belonging to the genera Mucor, Aspergillus, Penicillium, Alternaria, Rhizopus and Fusarium.
In view of these findings, the microbiological balance in the soil samples examined is disturbed, with beneficial microorganisms lying below the norm, while harmful micromycetes are partly above the norm, potentially leading to a range of plant diseases. The absence of free-living nitrogen-fixing bacteria indicates reduced nutrient uptake and biological activity in the soil.
To eliminate these imbalances, it is recommended to use local microbiological and organic fertilizers. This strategy aims to normalize and improve the soil microflora in the cotton fields of
the Jizzakh region, promote healthier conditions for plant growth and mitigate the effects of harmful microorganisms on plant health.
REFERENCES
1. Dokic, L., Savic, M., Narancic, T. and Vasiljevic, B. (2010). Metagenomic Analysis of Soil Microbial Communities. Archives of Biological Science-Belgrade 62(3): 559-564.
2. Brader, G., Compant, S., Vescio, K., Mitter, B., Trognitz, F., Ma, L. J., &Sessitsch, A. (2017). Ecology and genomic insights into plant-pathogenic and plant-nonpatho-genic endophytes. Annual Review of Phytopathology, 55(1), 61-83.
3. Iriondo, M. J., Maxted, N., &Dulloo, M. E. (Eds.). (2008). Conserving plant genetic diversity in protected areas: population management of crop wild relatives. CABI, ISBN: 978 -1 -84593- 282-4.
4. Zvyagintsev D.G. (1991) Methods of soil microbiology and biochemistry. Moscow.- 350 p.
