CALORIMETRIC STUDY OF THE INTERACTION BETWEEN EXTRACTS OF BRACHIARIA PLATYPHYLLA AND SOIL

SESTO CABRAL MARIA EUGENIA; SIGSTAD E.E.

Jornada; Biocell.; 2008

Brachiaria platyphylla (Munro ex C. Wright) Nash has invaded cultivated fields in Tucumán province, Argentina, with the consequent economic damage to producers. To understand its invasivity, EtOAc and MeOH extracts of its aerial parts were incubated with soil to further investigate chemical, microbiological and calorimetric modifications. Also, soil samples from invaded and non invaded areas were studied. An isothermal heat conduction calorimeter was used to obtain microbial growth curves. Invaded soil had higher values of organic carbon (OC), extractable phosphorus (P), colony formation units (CFU g-1) and pH than the non invaded one. Major modifications were observed with 83 mg kg-1 of both extracts and 250 and 500 mg kg-1 of MeOH extract. Microbial activity was much higher than control, indicating that microorganisms degrade carbon sources of extracts to increase microbial biomass. This could be related to the high invasivity of this plant species of the Poaceae family.