Efficiency Evaluation of some Rhizobacteria Isolated from Egyptian Soils, In vitro as Biofertilizers.

Abstract

Nitrogen (N), Phosphorus (P) and Potassium (K) are the major essential macro-nutrients for plants. The ability of soil bacteria to provide available forms of these nutrients to plants is an important feature in the bacterial strain used as a biofertilizer. In this study, fifteen isolates of Azotobacter spp were isolated. The efficiency levels of the N 2 -fixation were tested, the isolates reduced acetylene at rates of 6.348 -1381.023 nmoles C 2 H 4 /ml/day. The most active isolate was No. AZ 8 that identified as Azotobacter chroococcum MF135558. Twenty-one phosphate-solubilizing bacteria (PSB) were isolated and solubilization efficiency % (SE%) of each isolate was determined by spot inoculation technique. Five isolates (PSB 3, PSB 7, PSB 8, PSB 12 and PSB 14) were chosen due to their high solubilization efficiency % (SE%) 182. 35, 173.33, 222.22, 170.00 and 194.11 %, respectively. The five P-solubilizing bacteria were tested for their ability to solubilize P from tri-calcium phosphate and rock phosphate in liquid Pikovskaya's medium. The highest quantity of released phosphorus in actively growing culture was 36.52 mg/100 ml after 28 days of incubation and 1.095 mg/100 ml after 3 days of incubation on tri-calcium phosphate and rock phosphate, respectively by isolate PSB 14 which was identified as Klebsiella oxytoca MF135559. Five isolates of K-releasing bacteria (KRB) were isolated on Alexandroov's medium and were tested to release K from mica-muscovite. All the tested isolates can release potassium from mica but not in equal efficiency. The most efficient isolate namely KRB-2 could release 7.05 ppm after 6 weeks of incubation. It was identified as Rhizobium pusense MF135560.

Studying the Ability of some Bacteria Isolated from Egyptian Soils to Fix Nitrogen and Solubilize Phosphate, In Vitro

“…This may because of a consequent oxidation of organic acids created in culture media and/or to the development of natural materials at the expense of organic acids formerly made. The gotten outcomes are in agreement with those of Hauka et al (2017) and Walpola et al (2014). Table (3) showed the variations in water-soluble phosphorus values as affected by the activity of PSB on tricalcium phosphate.…”

“…The diminution in P content with the advance of incubation period could be due to the consumption of P causing the changeable levels of P discharge, accessibility of soluble phosphorus in the culture medium might also has an inhibitory effect on further phosphate solubilization, excretory toxic yields may also responsible for such weakening in P-solubilization. The existing outcomes are matched with that of Hemalatha et al (2013), Walpola et al (2014) and Hauka et al (2017). The maximum amount of liberated phosphorus in actively developing culture was verified by isolate PSB 5 which was used as PSB inoculant in further experiments.…”

The Integration of Bio and Organic Fertilizers Improve Plant Growth, Grain Yield, Quality and Metabolism of Hybrid Maize (Zea mays L.)

“…The results showed that A. chrococcum reached its maximum activity after 28 days of incubation, whereas B. circulans reached the maximum activity after 14 days of incubation, then was decreased. The decrease in P content with the advance of the incubation period could be attributed to the utilization of P resulting in the fluctuating levels of P release, and availability of soluble P in the culture medium might also have an inhibitory effect on further P solubilization [57][58][59][60]. Excretory toxic products may also responsible for such decline in P solubilization.…”

“…Generally, there was a rapid decrease in pH values within the first three days of the experiment, reflecting the high activity of organic carbon degradation bacteria leading to organic acids releasing which mainly contribute to the increasing pH value. The increase in pH might be due to a subsequent oxidation of organic acids produced in the culture media or might be due to the formation of other natural substances [57][58][59]. Moreover, both bacterial strains can effectively produce IAA which may contribute to improving the nutrition of maize plants.…”

Dual Inoculation with Azotobacter chroococcum MF135558 and Klebsiella oxytoca MF135559 Enhance the Growth and Yield of Wheat Plant and Reduce N-Fertilizers Usage

“…Azotobacter chroococcum MF135558 (N2-fixing bacteria), Klebsiella oxytoca MF135559 (P-solubilizing bacteria) and Rhizobium pusense MF135560 (K-releasing bacteria) were isolated and identified by Hauka et al, (2017). Experimental design A field experiment was carried out in Fac.…”