Effect of plant species and mycorrhizal inoculation on soil phosphate-solubilizing microorganisms in semi-arid Brazil: Growth promotion effect of rhizospheric phosphate-solubilizing microorganisms on Eucalyptus camaldulensis

Abstract

The Jaíba Project is an irrigation enterprise in the north of the state of Minas Gerais and its native vegetation is a dry deciduous forest called woody Caatinga. Two experimental areas (1.5 ha/site) were established in a degraded area using native species intercropped with Eucalyptus camaldulensis in three blocks at random. In each experimental area six plots, randomly distributed in each of the three blocks were cultivated as follows: In area A: (1) Platymenia reticulata Benth (2) P. reticulata inoculated with Rhizobia and spores of Arbuscular Mycorrhizal Fungi (AMF) (3) Eucalyptus camaldulensis Dehnh, (4) Eucalyptus camaldulensis + AMF (5) P. reticulata + Eucalyptus camaldulensis + Tabebuia sp. (6) P. reticulata. (Rhizobia + AMF) + Eucalyptus camaldulensis (AMF) + Tabebuia sp. In the other area plots were cultivated as follows: (1) Schinopsis brasiliensis Engl (2) Schinopis brasiliensis + AMF (3) Eucalyptus camaldulensis (4) Eucalyptus camaldulensis + AMF (5) Schinopis brasiliensis + Myracrodruon urundeuva Fr. Allen + Eucalyptus camaldulensis (6) Schinopis brasiliensis (AMF) + Eucalyptus camaldulensis (AMF) + Myracroduon urundeuva. Soil samples were taken in the root zone of each cultivated plant and analyzed in relation to the number of phosphate solubilizing microorganisms (PSM) and AMF spores. The results showed that the number of PSM and MF spores was significantly higher in the inoculated Eucalyptus rhizosphere, when compared to the native species and also to the non-inoculated Eucalyptus plants. The treatment where PSM and AMF populations were increased the plants also showed greatest height and diameter growth and it was not related to soil phosphatase activity. The growth promotion effect of PSM and AMF was confirmed under greenhouse conditions where the double inoculation improved the dry matter production and phosphorus content. Double inoculation of PSM and MF was recommended to Eucalyptus plants cultivated in semiarid land.