Numbers of culturable bacteria in soil under mineral or organic cultivation: comparison of Hattori's 'FOR' and standard dilution plate methods
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Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, P.O. Box 201, 20-290 Lublin 27, Poland
New York University, Biology Department, Laboratory of Microbial Ecology, 100 Washington Square East, New York, NY 10003-6688, U.S.A.
Technical University, Nadbystrzycka 40, 20-618 Lublin, Poland
Int. Agrophys. 2006, 20(4): 277–288
Two concepts and methods for determining the number of culturable bacteria were compared in soil under conventional ie mineral fertilizers, herbicides, fungicides or organic management ie manure or compost, mechanical or manual weeding. In the first method, colony-forming units (CFUs) of bacteria were counted after 14 days of incubation of soil dilutions on two different media ie diluted nutrient broth agar (DNBA) and soil extract agar (SEA). In the second method, the First Order Reaction (FOR) model was used to determine the CFUs of bacteria that were counted 7 times on successive days after plating the soil dilutions on the media. The CFUs were also expressed on the basis of 1 g of fresh soil, 1 g of oven-dry soil, 1 cm3 of soil, 1 cm3 (ml) of soil dilution, 1 cm3 of soil porosity, and 1 cm2 of pore surface. The numbers of bacteria were compared with the organic carbon content of the soils, as soil organic matter was assumed to be the major substrate for the growth of the bacteria. The content of carbon was 0.96% (in soil receiving mineral fertilizers) and 1.34% (in soil receiving organic fertilizers), resulting in a comparative ratio of 0.96:1.34 = 0.72.