Cellulolytic Fungi Populations in Stubble and Soil as Affected by Agricultural Management Practices

ABSTRACT

The aim of this study was to evaluate the effects of different agricultural management practices on the dynamics of cellulolytic fungi populations. The treatments considered were two cropping sequences: (l) corn, wheat-soyabean, soyabean (C-W/S-S) and (2) wheat-soyabean (W/S), and three tillage systems: (1) chisel tillage (ChT); (2) no tillage (NT) and (3) autumn plough-no tillage (AP/NT), all of them evaluated at two depths, 0–5 cm and 5–10 cm. Soil samples were taken after wheat harvest. Crop residues were removed from the soil, and soil and residues were weighed separately. Soil organic matter (SOM), pH and counts of viable cellulolytic fungi (CF) were determined. The CF were isolated by the dilution plate and the washing method and identified. The residue quantity and SOM were higher in the C-W/S-S rotation than in the W/S rotation and higher in NT than in ChT. The pH values were less acid in the C-W/S-S rotation in NT. The counts of viable cellulolytic fungi associated with crop residues increased as the treatment progressed; expressed either as per g of stubble or associated with the stubble in 1 g of soil. In the last year of the study, differences between tillage systems were observed: CF were most numerous in NT combined with the C-W/S- S rotation, and in AP/NT and NT in the W/S rotation. Fungal species of Penicillium, Trichoderma, Aspergillus, Fusarium, Gliocladium, Monocillium, Rhizopus, Acremonium, Alternaria and Dreschlera were isolated. The Penicillium species were isolated more frequently by dilution method. Differences between the two crop rotations, with bigger variety of Fusarium species associated with residues in the C-W/S-S rotation were observed. The results show the dynamics of cellulolytic fungal populations associated with stubble and their potential use to characterize the soil changes produced by different management practices.