Wednesday, November 15, 2006

Microbial Dynamics During Establishment of Turfgrass on Sand-base and Soil Root Zones.

David Zuberer1, Tony Provin2, Richard White2, and Annette Fincher2. (1) Texas A&M Univ., Soil and Crop Sciences Dept., 2474 TAMU, College Station, TX 77843-2474, (2) Soil & Crop Sciences Dept., Texas A&M Univ., College Station, TX 77843-2474

Several studies have been conducted to monitor populations of soil bacteria and fungi during establishment of turfgrasses on soil or sand-based root zones.  Monitored sites included bermudagrass established on a native soil amended with 0, 15 and 90 tons of composted municipal wastes and biosolids from Austin Texas (Dillo Dirt) and several sports fields on the Texas A&M campus.  Sports fields included Kyle Field (sand-base football field), TAMU Soccer Complex (washed sod over sand base), Olsen Field (washed sod over sand-base baseball field) and an intramural field on native soil.  With the exception of Olsen Field (1-yr sampling) all sites were sampled on an approximate monthly basis for two years.  Bacteria and fungi were enumerated by dilution plating using 10% Tryptic Soy Agar and Martin’s Medium respectively.  The results from these studies indicated that microbial populations established quickly in the surface 10 cm of the turfgrass fields even if they were established with washed sod laid over a base of pure sand.  Bacterial numbers ranged between log10 7.4 to 8.12 with an average of 7.72 +/- 0.18 at the soccer complex.  Some seasonality was observed but numbers tended to fluctuate mainly in response to soil moisture at time of sampling.  Similar numbers were observed at the other sand-based fields.  Microbial numbers were slightly larger (log10 7.5-8.5) in the native soil of the compost-amended plots.  Mean numbers of bacteria were log10 7.84, 7.91 and 7.96 for the 0, 15 and 90 t/ha compost rates respectively.  The results of these studies showed that microbial populations under warm-season turfgrass on soil or sand-based rootzones were robust and resilient maintaining high numbers throughout both the active growth and dormancy periods.   Further, they suggest that there would be little, if any, need for addition of microbial inoculants as is frequently recommended by some turfgrass practitioners.