Document Type : Research Paper
Authors
1 Department of soil science engineering, Collage of Agriculture and Natural Resources,, University of Tehran, Karaj, Iran
2 Department of Soil Science, College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran.
3 Department of Environmental Engineering, Faculty of Environment, University of Tehran, Tehran, Iran.
Abstract
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EXTENDED ABSTRACT
Periphytic biofilms live by adhering to hard substrates in aquatic ecosystems, especially in shallow, flooded areas. They are named according to the substrate on which they are found. The primary components of periphyton formation (algae, bacteria, fungi, metazoans, protozoa) play a crucial role in nutrient cycling in aquatic ecosystems, including rice fields. These biofilms act as a high active biological buffer for continuous nutrient transformations, sedimentation and release, effectively serving as a sink/source of nutrients between the soil and the water layer. It can be used as a potential biofertilizer. Studies have shown that bacteria and fungi can release potassium by breaking down or altering the structure of potassium-bearing minerals (such as mica and feldspar). Considering that research related to the periphyton is very limited in Iran and all over the world and that such studies have only recently begun in Iran, understanding the impact and performance of periphyton is essential. On the other hand, the complex composition of the periphyton microbial community may contain elements or interactions that have not been identified yet. Therefor, examining the entire biofilm in terms of potassium dissolution, which is one of the essential elements for plant growth, is highly effective.
To conduct this research, samples were collected from three different locations in Guilan Province. Paddy field samples, including epipelon and epiphyton, as well as fallow soil samples, were taken from the soil surface in three replicates. These samples were transferred to the laboratory in an ice box and then recultured in BBM medium. A modified BBM medium with muscovite and phlogopite mica was used for quantitative analysis of potassium solubilization. In this process, 10 ml of periphyton grown in the laboratory were inoculated into 100 ml of medium containing 2.5 g L-1 of muscovite/phlogopite minerals.
The necessary greenhouse conditions for this test include: a temperature of 28 ℃, lighting at 5000 lux, a 12/12hour light/dark cycle, and daily aeration by manual shaking. This experiment, which lasted for three weeks, involved sampling at 7-day intervals to measure the EC, pH and soluble K parameters of the solution.
The amount of potassium dissolution in medium with phlogopite treatments was somewhat higher than in treatments whit muscovite. According to the potassium levels in all treatments, we observed a significant increase in soluble potassium. The potassium level in most treatments were observed on the 14th day and the highest levels being 14.33 and 14.26 mg L-1 for the periphyton number 15, indicating a 3.6-fold increase compared to the control. Next periphyton sample 17 showed a 3.5-fold increased compared to the control, whit soluble potassium of 14.21 and 14 mg L-1 both samples mentioned above belong to the Vajargah rice field. This indicates a very high rate of periphyton growth in the early days, which increased the amount of soluble potassium due to biomass growth. As periphyton grows, bacterial and fungal communities capable of dissolving potassium release this nutrient from the mineral structure. By the 14th day, we observed a decrease in soluble potassium, which may indicate the absorption of potassium into the periphyton structure.
Samples numbered 19, 20 and 21, related to fallow soil, did not have high potassium dissolution but still showed a significant difference compared to the control. But this shoed an 83% increase compared to the control.
Regarding the pH results, we observed an increase in acidity compared to the initial days of incubation, which increased simultaneously with the growth of periphyton. This may indicate an increase in photosynthetic activity. According to the EC results, all treatments caused a decrease in the EC of the medium, likely due to the increase in periphyton biomass and the resulting absorption of soluble substances by the periphyton.
The results of this research demonstrated that various types of epipelons, epiphytons and fallow soil microbiomes possess a notable ability to release potassium from silicate minerals.
Conceptualization, H.A. Alikhani. and M. Leylasi-Marand.; methodology, H.A. Alikhani.; software, M. Leylasi-Marand.; validation, H.A. Alikhani. and S. Shariati ; formal analysis, M. Leylasi-Marand.; investigation, H.A. Alikhani. and S. Shariati; resources, M. Leylasi-Marand.; data curation, M. Leylasi-Marand. S. Shariati; writing—original draft preparation, M. Leylasi-Marand.; writing—review and editing, M. Leylasi-Marand and S. Shariati.; visualization, H.A. Alikhani.; supervision, H.A. Alikhani. and S. Shariati.; project administration, H.A. Alikhani., S. Shariati and M. Leylasi-Marand.; funding acquisition, H.A. Alikhani and M. Leylasi-Marand. All authors have read and agreed to the published version of the manuscript.
Not applicable
This work is based upon research funded by Iran National Science Foundation (INSF) under project No.4000736.
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The authors declare no conflict of interest.
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