Evaluation of relationships between soil properties and total bacteria and fungi in soils of Guilan

Microorganisms in soil usually make up less than one percent of the total soil volume and their effect on soil is very high. One of the indicators of soil quality is a sufficient number of microorganisms and their activity in different soils which depends on soil properties. In order to determine the relationship between the bacteria and fungi, with some soil properties 50 soil samples were collected from different areas of Guilan province. Total population of bacteria and fungi and some soil properties were measured in soil samples. For counting the total bacteria and fungi a series dilution of soil and a tenth of milliliter of dilutions spread in three replicates on nutrient agar and martin Rose Bengal Agar petri dishes respectively for enumeration of total bacteria and fungi. Colony count of bacteria and fungi was carried out after a week of culture. The total population of bacteria and fungi were counted and their relationships with soil properties was investigated. Results showed that 50 percent of the samples with electrical conductivity less than or equal to 1 (dS m), their total bacterial population were more than 108 cells per gram. The total population of fungi in all electrical conductivity levels varied, mostly between 104 to 105 cells per gram. About 84 percent of the samples had moisture content of more than 10 percent. In this moisture range, the total population of bacteria of most samples (62 percent) were between 107 to 108 cells per gram. In different percentages of organic matter, in more than 50 percent of the samples the total population of bacteria varied between 107 to 108 cells per gram. In all of organic matter ranges, more than 50 percent of samples had the total population of fungi with 104 to 105 cells per gram. In all ranges of cation exchange capacity (except in less than 10 Cmolc per kg) most of the samples contained the total bacterial population against 107 to 108 cells per gram. In the cation exchange capacity range between 10 to 20 Cmole per kg, the total population of fungi varied in 69.2 percent of the sample between 104 to 105 cells per gram. In all domains of available phosphorous, total bacterial population in the most of samples was between 107 to 108 cells per gram. Distribution of total population of fungi in the range of available P between 10 and 15 mg kg, was higher than other domains.