Microbial activity and fungal composition of composted animal manure suppressive to soil-borne pathogens

Abstract

Microbial composition in composted organic materials is an important factor to be considered when producing compost for disease suppression. The objectives of the study were to evaluate both microbial activity and fungal composition in composted animal manure with varying degree of suppressiveness towards soilborne fungal pathogens. Microbial activity of composted cattle, pig, poultry and sheep manure and loamy field soil was tested by means of hydrolysis of fluorescein diacetate (FDA). Fungal populations in these composts were also studied by serial dilution technique. Microbial activity was significantly higher (P<0.05) in poultry, pig and cattle manure compost as well as field soil compared to composted sheep manure which had the lowest microbial activity. High fungal populations were recorded in cattle (62%), poultry (63%) and pig (65%). Trichoderma harzianum, T. viride, Talaromyces trachyspermum and Penicillium verrucosum were the most common species isolated from cattle, poultry and pig manure composts. Significantly (P<0.05) less species were observed in both control (48.6%) and composted sheep manure (12.5%), with Humicola sp. being the only species isolated from this compost. Microbial composition of composted animal manure is an ideal indicator of the suppressiveness of such composts towards soilborne pathogens.