Alfalfa (Medicago sativa L.) was selected for the exper- iment because its extensive, widely branched root system provides a large root surface for the growth of microbial populations. The PAHs-degrading bacterial inoculums, which mainly contained two strains, Flavobacterium sp. and Bacillus sp., were cultivated in tryptic soy broth (Burd et al., 2000) at 37°C for 2 days. About 107 cells were inoculated to one gram of soil on a dry basis. The doses of cattle manure and sewage sludge amended were 0.5%, 1%, 2% and 0.05%, 0.1%, 0.2% (m/m), respectively.
The pots (12 cm in diameter, 18 cm in height) with 3 kg dry soil each were placed into a greenhouse. Alfalfa seeds were sterilized in 10% (V/V) H2O2 for 20 min and washed three times with distilled water. Fifteen seeds were sown in four replicates and the seedlings were thinned to 10 seedlings after germination. The growth conditions were: 25°C during a 12 hr day and at 20°C during a 12 hr night. The light intensity was 4500–7300 lux and the soils were watered daily and adjusted to approximately 50% of the water holding capacity during
Alfalfa (Medicago sativa L.) was selected for the exper- iment because its extensive, widely branched root system provides a large root surface for the growth of microbial populations. The PAHs-degrading bacterial inoculums, which mainly contained two strains, Flavobacterium sp. and Bacillus sp., were cultivated in tryptic soy broth (Burd et al., 2000) at 37°C for 2 days. About 107 cells were inoculated to one gram of soil on a dry basis. The doses of cattle manure and sewage sludge amended were 0.5%, 1%, 2% and 0.05%, 0.1%, 0.2% (m/m), respectively.The pots (12 cm in diameter, 18 cm in height) with 3 kg dry soil each were placed into a greenhouse. Alfalfa seeds were sterilized in 10% (V/V) H2O2 for 20 min and washed three times with distilled water. Fifteen seeds were sown in four replicates and the seedlings were thinned to 10 seedlings after germination. The growth conditions were: 25°C during a 12 hr day and at 20°C during a 12 hr night. The light intensity was 4500–7300 lux and the soils were watered daily and adjusted to approximately 50% of the water holding capacity during
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