Isolation of Phosphate Solubilizing Bacteria from White Lupin (Lupinus albus L.) Rhizosphere Soils Collected from Gojam, Ethiopia

Phosphorus is one of the least available and the least mobile mineral nutrients in soil for plant growth. However, it is vital for plants and they absorb only inorganic form of phosphorous but the level of inorganic phosphorus is very low in soil because most of the phosphorous is present as insoluble forms. Unlike nitrogen, there is no large atmospheric source that can be made biologically available to plants. P chemical fertilizer is widely applied in agricultural production. However, a large proportion of these fertilizers are also converted to insoluble form leads to low-fertilizer efficiency where the volume of phosphatic fertilizers as low as 15-20% are only utilized by plants due to fixation of P in acidic and alkaline soils.

Phosphorus deficiency is the most important problem of Ethiopian soils and more than 70-75% of highland soils are characterized by phosphorus deficiency. Around 70% of Ethiopian vertisols have available phosphorus below 5 ppm, which is very low for supporting good plant growth; and, fixation in vertisols is related more to calcium, than Al3+ and Fe3+. Yield is usually low under traditional farming system because of poor cultural practices that is compounded with poor soil fertility.