Track 2-11: Plant Nutrition and Nutrient Cycling
Description
Phosphorus although abundant is among the most limiting macro plant nutrients in some soils. Deficiencies are often seen as purpling of leaves due to unavailability of PO4 in soil solution. In soil solution PO4 solubility is pH dependent; at pH < 6, it is often bound to Fe or Al, while at pH > 7 it forms insoluble complexes with Ca, Mg, K or Na making it unavailable to plants (Brady 2002). Soil organic P requires mineralisation then solubilisation by the enzyme phosphatase before being available. Botswana soils due to the low rainfall (< 450 mm/yr) are characterised by high pH and salt pans scattered all over the semi-arid and arid landscape. Cultivation of most of these soils often results in P deficient crops (Leuschner and Manthe 1996). However, in grassland areas of the Okavango, very few grasses show P deficiency. Studies from other areas indicate that some grasses habour PO4 solubilizing bacteria in their rhizosphere that help them in their P sequencing quest (Duponnois et al. 2005). This study was set up to study the PO4 solubilising bacteria of the Okavango Delta at Seronga. The study also looked at possible mechanisms of solubilisation employed by the bacteria. In the long run, the study will also attempt to use these bacteria on locally grown staple cereal, sorghum (Sorghum vulgare).
Included in
Soil Phosphate Solubilising Bacteria of the Okavango Floodplains, Botswana
Phosphorus although abundant is among the most limiting macro plant nutrients in some soils. Deficiencies are often seen as purpling of leaves due to unavailability of PO4 in soil solution. In soil solution PO4 solubility is pH dependent; at pH < 6, it is often bound to Fe or Al, while at pH > 7 it forms insoluble complexes with Ca, Mg, K or Na making it unavailable to plants (Brady 2002). Soil organic P requires mineralisation then solubilisation by the enzyme phosphatase before being available. Botswana soils due to the low rainfall (< 450 mm/yr) are characterised by high pH and salt pans scattered all over the semi-arid and arid landscape. Cultivation of most of these soils often results in P deficient crops (Leuschner and Manthe 1996). However, in grassland areas of the Okavango, very few grasses show P deficiency. Studies from other areas indicate that some grasses habour PO4 solubilizing bacteria in their rhizosphere that help them in their P sequencing quest (Duponnois et al. 2005). This study was set up to study the PO4 solubilising bacteria of the Okavango Delta at Seronga. The study also looked at possible mechanisms of solubilisation employed by the bacteria. In the long run, the study will also attempt to use these bacteria on locally grown staple cereal, sorghum (Sorghum vulgare).
