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Soil Microbial Communities and Enzyme Activities under Various Poultry Litter Application Rates

^a USDA-ARS, Cropping Systems Research Laboratory, 3810 4th Street, Lubbock, TX 79415
^b USDA-ARS, Grassland, Soil and Water Research Laboratory, 808 East Blackland Road, Temple, TX 76502

View larger version (26K): [in a new window]   Fig. 1. This study investigated the soil microbial populations and enzyme activities in pasture and cultivated sites located in the Texas Blackland Prairie ecosystem, an important agricultural region encompassing 4.45 million ha. The region is known for its Houston Black Clay soil (fine, smectitic, thermic, Udic Haplustert), which is the representative soil for Texas, USA.

View larger version (59K): [in a new window]   Fig. 2. Soil microbial biomass carbon (A) and microbial biomass nitrogen (B) in pasture and cultivated sites as affected by different rates of poultry litter applications in 2002, 2003, and 2004 following the second, third, and fourth annual litter application, respectively. Bars with different letters are significantly (P < 0.05) different.

View larger version (91K): [in a new window]   Fig. 3. The activities of soil ß-glucosidase (A), -galatosidase (B), and ß-glucosaminidase (C) in pasture and cultivated sites as affected by different rates of poultry litter amendments in 2002, 2003, and 2004 following the second, third, and fourth annual litter application, respectively. Bars with different letters are significantly (P < 0.05) different.

View larger version (32K): [in a new window]   Fig. 4. Three-dimensional plots for the group of soil ß-glucosidase (y axis), -galactosidase (x axis), and ß-glucosaminidase (z axis) activities as affected by different rates of poultry litter amendments. Plots show the results in 2002 and 2004 following the second and fourth annual litter application, respectively.

View larger version (64K): [in a new window]   Fig. 5. Soil arylsulfatase activity (A) and alkaline phosphatase activity (B) in pasture and cultivated sites as affected by different rates of poultry litter amendments in 2002, 2003, and 2004 following the second, third, and fourth annual litter application, respectively. Bars with different letters are significantly (P < 0.05) different.

View larger version (22K): [in a new window]   Fig. 6. Principal component analysis (PCA) of the soil microbial community shifts in pasture sites as affected by different poultry litter application rates according to the abundance of fatty acid methyl ester (FAME) indicators of fungal, bacterial, and actinomycetes groups. Each symbol specifies the year of sampling (02 = 2002, 03 = 2003, 04 = 2004), and the litter rates (C = control, L = 6.7 Mg ha–1, H = 13.4 Mg ha–1). The PCA provides a comparison of the fungal to bacterial (F:B) populations ratio among the soils. The soils located near the microbial group specified indicate they have higher relative abundance of such microbial group.

View larger version (10K): [in a new window]   Fig. 7. Principal component analysis (PCA) of the soil microbial community shifts in cultivated sites as affected by different poultry litter application rates for 2003 and 2004 samplings according to the abundance of fatty acid methyl ester (FAME) indicators of fungal, bacterial, and actinomycetes groups. The symbols indicate the different poultry litter application rates applied to the soils (open symbols = 0, 4.5, and 6.7; closed symbols = 9.0, 11.2, and 13.4 Mg ha–1). The PCA provides a comparison of the fungal to bacterial (F:B) populations ratio among the soils. The soils located near the microbial group specified indicate they have higher relative abundance of such microbial group.