Soil Phosphorus Research Paper

Chapter-1

INTRODUCTION

1. Introduction

Phosphorus (P) is one of the most essential component of the nucleic acid structure which regulates protein synthesis and plays an important role in biological growth and development. Being the most limiting macronutrient after nitrogen, P plays a significant role in increasing root ramification and strength as well as provides vitality and disease resistance. Along with these essential functions, P is also associated with complex signal transduction, macromolecular biosynthesis, energy transformations and respiration in the plant (Khan MS et al. 2010). Soil P exists in various chemical forms including inorganic P (Pi) and organic P (Po) which differs in their behavior and fate

Soil microorganisms are effective in releasing P from organic and inorganic pools of total soil P through mineralization and solubilization. The major mechanism of phosphate solubilization is the production of organic acids. The major mechanism of phosphate solubilization is the production of organic acids. Among the organic acids produced, gluconic, formic acid, 2-ketogluconic, citric, oxalic, lactic, isovaleric, succinic, glycolic and acetic acids produced from P- solubilizing bacteria. Production of organic acids results in the lowering of pH in the surroundings and many reports suggests a positive correlation between lowering of pH and mineral phosphate solubilization. Some of the alternate mechanisms suggested are production of chelating compounds, inorganic acids like sulphuric, nitric and carbonic acids. Another attractive application of P-dissolving enzymes is the mineralization of soil organic P compounds through phytate degradation mediated by the enzyme phytase, which specifically causes release of P from phytic acid. Phytate is a major component of organic P in soil. There are several reports of phytase producing organism. Richardson AE (1997) reported insoluble P solubolization by secreting phytase enzyme in Pseudomonas sp. (Richardson AE and Hadobas PA, 1997). Several species of microorganisms are able to secrete

Thus, the amount of P liberated by them is generally not sufficient for a substantial increase of in in situ plant growth. Therefore, inoculation of plant by desire microorganism at adequate amount than the normal found in soil is necessary to take advantage of the property of phosphate solubilization for plant growth and yield enhancement (Rodrigues H and Fraga R, 1999).

OBJECTIVES

In the context of above observations, the present investigation was carried out with the following objectives:

1.1. Objectives of the Study

• To isolate the phosphate-solubilize bacteria from rhizosphere of maize plants,

• To detect the phosphate-solubilizing ability,

• To characterize the microorganisms at the phenotypic and genotypic level,

• To study the diversity of phosphate solubilizing bacteria,

• To examine the production of organic acids,

• In addition, this study was to examine the effect of phosphate-solubilizing bacteria as inoculants on plant growth and yield and may be used as biofertilizer.

• We also hypothesize that the combined effect of microbial strain can also give better result as compared to the single