Abstract

Phosphorus replenishment, particularly in smallholder agriculture, remains a challenge as it is mainly fertilizer dependent. While the use of soluble mineral phosphate fertilizers is the obvious best means to combat phosphate deficiency in Cameroon, their use is limited by their high cost and availability at farmer’s level. This study was carried out aimed at maintaining the fertility of Cameroon soils by biological means, in order to improve agricultural production, using low inputs technology. Isolates were obtained from oil palm (Elaeis guineensis) root fragments and rhizospheric soils and their activity in mobilizing phosphate from insoluble sources was evaluated on agar plates and liquid culture media containing sparingly soluble phosphates. At the end of incubation time, it appeared that, phosphate solubilization resulted from a combined effect of pH decrease of the media and organic acids production. Furthermore, each of the tested isolates was able to produce at least one of the most important organic acids such as citrate, malate and tartrate. Among the ten isolates tested, three were identified as Pseudomonas fluorescens and would be considered as potential biofertilizers.

Key words: Carboxylic acids, oil palm rhizosphere, phosphate solubilization, pH decrease, Pseudomonas fluorescens.