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Essay: Augmenting PGPR and PGPF groups in a Wicking bed system

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  • Published: 5 August 2022*
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Background

Agroecosystems are been studied extensively for the presence of the beneficial Plant Growth Promoting Microbes (PGPM), and their beneficial role in plant growth and health. PGPM, consisting mainly of two different groups – Plant growth-promoting Rhizobacteria (PGPR) and Plant growth-promoting Fungi (PGPF), colonize the roots or the Rhizosphere area of the plants in a mutualistic manner by solubilizing inorganic compounds, degrading and mineralizing organic compounds, secreting biologically active substances such as phytohormones, chelators, and antibiotics, among others, promoting plant growth.

Main objective

In this study, we propose to introduce biological growth amendments to the potting soil to augment the PGPR and PGPF groups of plants, specifically grown in a Wicking bed system.

Methodology

For the preparation of the rhizospheric sample, adhering soil was suspended in 10 ml sterile distilled water and dilutions were made. After that one gram of attached soil was taken, and dilutions were made by adding 10 ml water to the soil and then make 10x dilution. For isolation rhizobacteria strains, the soil was dissolved in distilled water and stirred using a magnetic stirrer. After isolation the agar was prepared and wait till it cooled, the next step is screening the diluted soil is done. After that, Isolation by spread plating method used, all the plates were placed in an incubator in the inverted form at 280C for 2 days. In the next two days, counting was done with the aid of a colony counter. The number of colonies present in the plate was used to determine the number of cells present in the dilution. Then, to purify the culture streaking method is used. The last step is the gram staining process to analyze the type of bacteria.

Results

The results are going to be reported after the study is conducted.

Conclusion

As same as results.

Keywords

PGPR; Rhizobacteria; Wicking bed; Biofertilizer

Introduction

Microbes are an essential part of the living soil, they transform nutrients in the soil, influence the health of the soil. In the presence of certain microbes, the growth of plants improves by various mechanisms. A direct mechanism can include the fixation of atmospheric nitrogen, synthesis of various phytohormones and enzymes, and solubilization of minerals in the soil. An indirect mechanism includes inhibiting phytopathogens. Therefore, plant growth- promoting rhizobacteria (PGPR) need to be harnessed and exploited for sustainable agriculture. In the rhizosphere the soil is connected to the plant roots, it is often extended a few millimeters off the root surface, thus it is an important environment for the plant and microorganism.

Rhizobacteria is a group of bacteria that lives in the soil, specifically near the roots of plants. This type of bacteria is used as biofertilizer, the rhizosphere of plants or inside the plant body (as endophyte) is colonized. So, plant growth is enhanced through the supply or availability of fundamental nutrients to crop plants. Rhizobacteria also affect the growth positively in other ways. First, it contributes to nitrogen fixation. Second, it dissolves phosphorus and iron. Third, it boosts the production of plant hormones. Fourth, it improves plants’ ability to withstand stress factors such as dehydration, salinity, mineral toxicity and the impact of pesticides. Fifth, it prevents bacteria that cause plant diseases such as fungi, nematodes, and viruses.

Microbial inoculums knowledge was applied for a long time through generation to generation of farmers. The industrial-scale of microbial inoculants in Malaysia have started late in the 1940s (Mohammadi, 2012) and it reached a peak in the 1970’s. Bio-fertilizers are environment-friendly, more efficient and economical. They perform more than one mechanism for accomplishing plant growth enhancement such as improving both crop yield & soil fertility. Unlike chemical fertilizers, biofertilizer depends on renewable resources of energy and does not contribute to environmental pollution. Because they are organic in nature, they consist of specific microorganisms in a concentrated form that originated either from the plant root nodule or from the soil of the rhizosphere. Biofertilizers emerged as environment-friendly inputs that are advanced for an agricultural crop production system, at the same time leads to sustainable agriculture. biopesticides are used as a seed or soil treatment, affecting plant nutrient availability and crop growth and yield. The diversity of microorganisms has the strength to solubilize & mobilize plant nutrient elements from the insoluble form by biological process. Moreover, fix atmospheric nitrogen. Using biofertilizers contributes to maintaining soil quality. This provides a low-cost approach to manage crop yield along with protecting the environment (Singh, 2016).

The wicking bed is containers with water reservoirs at the base. At the bottom of the wicking, water is drawn from the top like the wick to the surface of the bed through the natural osmosis of the soil or through the roots of the plants in the bed, which helps to feed the roots of the plants with water when needed, the area of the roots is always wet but not much in order to ensure that a sufficient quantity is provided To cross oxygen to the roots. It is a traditional irrigation system with a “self-water” feature. The type of wicking bed system used in the experiment is open wicking, it is the simplest type of bed wicking systems. Planting in open wicking beds is in the root zone, a ditch is dug under it and lined with a solid pool liner or plastic sheet, thus the water passes through the root zone and is hunted in a plastic sheet, so the soil becomes saturated. This explains why the volume of water is not only limited to the soil as it passes through the roots as well. The wet open bed allows the water to wake up, then sideways side and bottom of the tank. So, it gives plants with deep roots a suitable system. Moreover, they allow bacteria and worms to enter the system. (Semananda, 2016). There are some considerations in this system design. A wicking bed is constructed from the sides of the wood and a solid pool liner at the base to function as a water reservoir and it must be non- porous and carry water. The water reservoir is usually filled with a bottom layer of gravel, which contributes to making the water rise to the soil through the “capillary action” process as it provides moisture to plants. (They may be made of a plastic container, but they should not be prone to corrosion when in contact with soil and water). The wicking bed should contain a reservoir with a depth of about 15-30 cm, and a depth of soil approximately 20 to 40 cm. The depth of the reservoirs must be less than the depth of the soil. (Deep reservoir depth will prevent feeding the root zone.) The soil required for a wicking bed to be friable sandy soil. After planting the seedlings for the first time in, surface irrigation is needed for a short period and once the plant grows there will be no need for irrigation unless the reservoir becomes empty, or before the reservoir is empty it must be filled.

Conceptual framework

Appearance of rhizobium

Nitrogen fixing bacteria

Soil characteristic

Plant growth

Biological nitrogen fixation is considered to be one of the major mechanisms by which plants benefit from the association of its microbial partners. The relation is the rhizobia gets the carbon fixed by the plant and on the other hand the plant gets nitrogen fixed by the rhizobia. Also, the characteristic of the soil is playing a role in growing the plant in a better way by containing a microorganism.

Literature Review

The soil is a full environment of various microorganisms, that contain beneficial bacteria that promote the growth of plants by colonizing the plant root, this method is used to develop the agriculture in different regions of the world. These specialized bacteria are called plant growth-promoting rhizobacteria (PGPR). A study conducted by the National Institutes of health used an experimental study design (Non-RCT), indicates that biological fertilizers are a better solution than chemical fertilizers. Also, the process of isolating the rhizobacteria linked to plant roots helped in studying the properties of rhizobacteria like Elevation, Margin, Opacity, and Color (Khan F.M, 2018). Therefore, this led to an increase in the yield of economic plants like cauliflower in developing countries like Pakistan (Islamabad). The Authors recommend the identification of strains to species level & field studies before adoption by farmers in agricultural field practices. Similarly, a study conducted by Frontiers in Microbiology has used an experimental study design (Non-RCT), which showed that rhizobacteria influence plants as they enhance their responses against biotic & abiotic pressures. The characterization of 6 halotolerant PGPR that was isolated from the rhizosphere of durum wheat plants cultivated in hypersaline environments in the Dead Sea has produced a lot of growth-promoting traits (Randa N.A, 2019) compared with non-inoculated plants. This means halotolerant PGPR was able to reduce the negative impacts of great salinity on durum wheat seed germination and seedling growth, so it can help commercially in the crop’s productivity under saline conditions. Another study conducted by the same journal has used an experimental study design (Non-RCT), found that plant growth-promoting rhizobacteria from the Himalayan region improve interactions of plant–microbes when it is introduced to an agroecosystem because it increases the ecosystems sustainability, agricultural productivity, and environmental quality. By isolating & identifying PGPRs associated with maize results were positive. Hence, Nitrogen-fixing and Phosphorus solubilizing isolates are present among the natural population of rhizobacteria, which means that effectiveness of PGPR isolates with NP fertilizers indicates that chemical fertilizers rate or dose can be reduced by a combination of PGPR isolates with fertilizers so it is eco-friendly and cost-effective management strategy (Mahwish Z., 2015). Moreover, a study was conducted by the International Journal of Novel Research in Interdisciplinary Studies, used an experimental study design (Non-RCT). It illustrated that Nitrogen is a significant nutrient for plant growth, development, and reproduction. It is an element supplied by the mutual symbiosis of rhizobia in cultivated legume plants. The isolation of native N2 fixing rhizobia for Cowpea, Elephant, Lablab produce them as inoculants to increase legume production (Temam A.H, 2017). The study suggests that isolated rhizobium can be applied as a useful soil biofertilizer because it does not contain any chemical fertilizers which leads to sustainable agriculture, especially for developing countries like Ethiopia as they are dependent on agriculture. In addition, a study conducted in the UAE by the Emirates Journal of Food and Agriculture has used an experimental study design (Non-RCT). It showed that drought and salt-stress are two major factors preventing the productivity of plants in desert environments. The isolation of rhizobia in order to inoculate the leguminous crop plants can increase the efficiency of rhizobium- legume symbiosis & thereby productivity. According to (Samrudhi R.S, 2013) isolated rhizobia under high concentration of NaCl resulted in colonies even at great salinities as 40 dS m-1. And, after the inoculation period, the rhizobial isolates were capable of growing in potting soil & irrigated with saline water of up to 12 dS m-1. The survival of rhizobia in extreme environments indicated that isolation of rhizobia contributes to the productivity of the leguminous plants, thus agriculture is developed and be successful in the UAE that has a desert climate. In conclusion, conducting information about the issue of this study is a bit challenging in developing countries that lack the equipment and funding. However, research is a country in developed countries that can create a similar environment to study both crops.

2020-4-19-1587316717

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