Changes in enzyme activities and in the functional diversity of actinomycetes due to long term agricultural management

Long-term agricultural management alters soil organic matter, nutrient status, and potentially the decomposer community. We measured the abundance and activity of cellulose, chitin, and protease degrading bacteria, and total soil extra-cellular enzyme activity for cellulose (β-glucosidase), chitinase (N-acetyl-glucosaminidase), xylosidase, and phosphatase activity. By combining these methods, we could determine how bacterial decomposer abundance and function were altered by long-term management, and how the bacterial decomposer community relates to overall soil enzyme activity. We also measured microbial total fungal and bacterial biomass, soil organic carbon pools, and extractable nitrogen for supplementary comparisons. Soil samples were taken in June of 2010 from the Bad Lauchstädt field station’s Static Fertilization Experiment, under treatment for 108 years. Treatments include mineral (NPK) fertilizer (none or added at 140, 60, and 230 kg ha-1 yr-1) and manure addition (none, 20 T ha-1 2yr-1, and 30 T ha-1 2yr-1) in a full factorial experiment. We found that total cellulase activity and the abundance of cellulase degrading bacteria were higher in plots with manure addition. We observed the same pattern for total phosphatase activity, total chitinase activity, and the abundance of chitin degrading bacteria, although the trend was not statistically significant for total chitinase activity. These results suggest that long-term management does alter decomposition and that total soil enzyme activity reflects the abundance of decomposer bacteria