**6. Conclusion**

The soil is a good reservoir or habitat for microorganisms which might be beneficial to both plants and animals. Soil microbes help in aerating the soil by increasing the pore sizes thus increasing the rate of percolation. The relevance of soil microorganisms to crop growth and productivity cannot be overemphasize. They enhance crop growth and productivity both in stress, low fertile and fertile soil by facilitating transformation, solubilization and mobilization of nutrients, and altering the physiological processes of plants.

In order to increase agricultural production in terms of cropping in the tropics without polluting or degrading the environment, most especially cropland soils, the use of biofertilizers and biopesticides composed of beneficial microbes should be encouraged among peasant and large scale farmers instead of synthetic fertilizers. Since they do not only improve the soil fertility but also assist the roots of plants in the absorption and uptake of nutrients from the soil.

**73**

**Author details**

Barachel Odaro-Junior Umukoro

provided the original work is properly cited.

Department of Botany, University of Ibadan, Ibadan, Nigeria

\*Address all correspondence to: umukorobacheloj@gmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Tropical Crops and Microbes*

*DOI: http://dx.doi.org/10.5772/intechopen.89531*

*Tropical Crops and Microbes DOI: http://dx.doi.org/10.5772/intechopen.89531*

*Microorganisms*

as auxins, abscisic acids, riboflavin, cytokinins, vitamins and lipochitooligosaccharides that promote plant growth in addition to fixing atmospheric nitrogen [139]. Other PGPR traits of *Rhizobia* and *Bradyrhizobia* assist in the production of phytohormones [140], release of siderophore [141], solubilization of inorganic phosphorus [142] and also act as antagonist against plant pathogenic microbes [143]. In the study of Kennedy *et al.* [144], a several number of non-symbiotic PGPR significantly increase the vegetative growth and grain yield of C3 and C4 plants such as rice, maize, wheat, cotton and sugarcane due to their interactions. The application of *Azotobacter* increased the yield of rice, cotton and wheat [145, 146]. In a field trial experimental study, Tran Van *et al*. [147] used *Burkholderia vietnamiensis* to inoculate rice and found out that it significantly increased the grain yields up to 8 t/ha. It has been reported that the species belonging to genus *Burkholderia* can

produce substances that are antagonistic to nematodes [148].

the genera *Pseudomonas, Bacillus* and *Rhizobium* [151].

altering the physiological processes of plants.

the absorption and uptake of nutrients from the soil.

Strains of bacteria belonging to the genera of *Pseudomonas, Rhizobium, Agrobacterium, Flavobacterium, Bacillus, Burkholderia, Aerobacter, Achromobacter, Erwinia* and *Micrococcus* have been found to have the ability to solubilize insoluble inorganic phosphate compounds such as rock phosphate, dicalcium phosphate, tricalcium phosphate and hydroxyl apatite [149, 150]. Tricalcium phosphate and hydroxyl apatite have been reported to be more degradable substrates than rock phosphate while the most powerful phosphate solibilizers are strains belonging to

The soil is a good reservoir or habitat for microorganisms which might be beneficial to both plants and animals. Soil microbes help in aerating the soil by increasing the pore sizes thus increasing the rate of percolation. The relevance of soil microorganisms to crop growth and productivity cannot be overemphasize. They enhance crop growth and productivity both in stress, low fertile and fertile soil by facilitating transformation, solubilization and mobilization of nutrients, and

In order to increase agricultural production in terms of cropping in the tropics without polluting or degrading the environment, most especially cropland soils, the use of biofertilizers and biopesticides composed of beneficial microbes should be encouraged among peasant and large scale farmers instead of synthetic fertilizers. Since they do not only improve the soil fertility but also assist the roots of plants in

*5.2.4 Phosphorus-solubilizing bacteria*

**6. Conclusion**

**72**
