Comparision the Effects of Earthworm Eisenia fetida Activity on the Physical and Biological Properties of Two Fine and Coarse Textured Soils

Earthworms improve physical, chemical and biological properties of soil by different mechanisms. The aim of the present greenhouse study was to compare the effect of Eisenia fetida earthworm on physical and biological properties of two fine and coarse textured soils with the application of organic matter and compaction treatments. The experiment was conducted as factorial with completelyrandomized design in 24 treatments and three replicates. Factors were as: three organic matter levels (without organic matter, 20 g of wheat straw and 20 g of cow manure per kg of soil), two soil textural classes (sandy loam and clay loam), two soil compaction levels (1.3 and 1.45 g cm-3) and earthworm( withor without).The soil samples were taken from Moghan areaand after mixing with organic materials and applying compaction levels, the soilswere filled in PVC tubes with 15 cm in diameter and 20 cm height. Ten Eisenia fetida earthworms were added for each tube at the beginning of incubation period. The samples were incubated at a temperature and moisture of 22 ± 4˚C and 50 to 70 % of field capacity for 6 months. At the end of the incubation period,disturbed and undisturbed soil samples were taken (with cylinder in diameter and height of 5 cm) to measure organic carbon, calcium and magnesium, mean weight diameter of aggregates, bulk and partical density, total porosity, saturationand field capacity, permanent wilting and available water contents, macro and micro pores, basal and substrate induced respirations, microbial biomass carbon and earthworms biomass. Results showed that the application ofearthworm increased porosity, macropores, saturation and field capacity water contents, permanent wilting and available water humidity, organic carbon, calcium and magnesium, mean weight diameter of aggregates, substrate induced respiration, microbial biomass carbon and reduced bulk density in both soil textural classes. Both used rate of organic matter significantly increased mean weight diameter of aggregates, calcium and magnesium, micro pores, field capacityand permanent wilting water contents, organic carbon, respiration, microbial biomass carbon, and reduced bulk density in both examined soil textural classes.The effects of straw on improving the above mentioned properties was more than the manure. The positive and significant correlation was found between calcium (0.558**) and organic carbon (0.511** ) with mean weight diameter of aggregates. The negative effect of compaction on soil properties in clay loam soil was more than sandy loam soil. The results of this study showed that the use of earthworms and organic matter improved soil physical and biological indicators in the compaction conditions.