Mobilization of organic and poorly soluble phosphates by Chaetomium globosum

A phosphatase and phytase releasing fungus Chaetomium globosum was isolated and tested under green house conditions (wheat as test crop) and in the field (pearl millet as test crop) in a loamy sand soil. The population build up and efficiency were compared under both sterilized and non-sterilized soil conditions. The 68% organic phosphorus (Po) in the experimental soil was present as phytin; less than 1% of P was present in a plant available form. Exploitation of plant unavailable (poorly soluble) P was higher in sterilized soil mainly due to increased population of C globosum. A gradual increase in microbial build up, between 7.5 and 16 times the inoculated population, occurred over a 4-week period. The test plants influenced acid phosphatase and phytase activity but resulted in no significant increase in alkaline phosphatase activity in the inoculated soil. The depletion of organic P was much higher than mineral P. The microbial contribution was significantly higher than the plant contribution to the hydrolysis of the different P fractions. The maximum effect of inoculation on different enzyme activities (acid phosphatase, alkaline phosphatase, phytase, dehydrogenase) was observed between 5 and 8 weeks of plant age. A significant improvement in plant biomass, root length, plant P concentration, seed and straw yield and seed P content resulted from inoculation. The results suggested that C globosum produces phosphatases and phytases, which mobilize P and enhance the production of wheat and pearl millet crops. (c) 2005 Elsevier B.V. All rights reserved.