REMOVAL OF INDICATOR MICROORGANISMS IN PASTURES AFTER BIOSOLID APPLICATION

Biosolid application to pastures is generally considered the best option of management for their organic amendments and plant nutrients. Particularly pastures converted into poor quality pastureland, as a result of early and over grazing, can be regained their productive capacity by biosolid application. The aim of the study was to obtain the bacterial inactivation after biosolid application to pastures during winter conditions. Four levels of biosolids were topically applied at rates of 25, 50, 100 and 200 t ha 1; one treatment was not amended that represented the control. The experimental design was a randomized block with three replications in the same plots during six months. Thermotolerant coliforms, Escherichia coli (E. coli), Enterococci and Salmonella ssp. were studied as the indicator microorganisms. Inactivation rates and times for 90% bacterial decline were obtained similar for each microorganism. While high inactivation efficiencies (96-100% for E. coli, 98-100% for thermotolerant coliforms and 99-100% for Enterococci) were achieved, Salmonella ssp. was not detected initially in soil and biosolid. Obtained results suggest that biosolid could be a safe and inexpensive substitute to inorganic fertilizer for poor quality pastures and standard application of biosolid on pastures is apparently at low risk