تعيين مقدار روي توده زنده ميكروبي در گروهي از خاك هاي آهكي

چكيده انگليسي :

۶ Determination of Soil Microbial Biomass Zinc in Calcareous Soils Parvin Zarei p zarei@ag iut ac ir 21 June 2014 Department of Soil Science College of Agriculture Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Prof F Nourbakhsh farshid@cc iut ac ir Abstract Many attentions have been spent on improving soil microbial biomass measurement techniques during last 40 years This is because of the inadequacy of the procedures which are traditionally used for bacterial and fungal population counting through extraction and culture and eventually enumeration of the colonies on the agar media Measurement techniques are generally supposed to be accurate and precise and can be used widely for a large number of various soils All the soil biomass measurement techniques represent a number of advantages and disadvantages and need to be implicated under controlled conditions Chloroform fumigation extraction CFE technique has been widely used in order to determine carbon nitrogen phosphorus and recently potassium in the soil microbial biomass and is expected to be compatible for some other elements which are normally accumulated in the soil microbial biomass The CFE technique is a direct procedure which has fewer disadvantages compared to other predominant soil microbial biomass measurement techniques The objectives of the present study were 1 determination the conversion factor for measuring soil microbial biomass Zn 2 comparison of two extractant DTPA and potassium sulfate in order to extraction and determination of Zn in fumigated and non fumigated soils 3 determination of soil microbial biomass potassium and 4 studying the relationships between Zn and K in soil microbial biomass For these purposes 10 soil samples were collected from calcareous soils of Isfahan and Chaharmahal provinces General soil characterization performed with proper methods and soil bacteria and fungi were enriched using nutrient broth NB and potato dextrose broth PDB respectively Enriched bacterial and fungal biomasses in the broth media were digested and Zn was measured in the biomass by atomic absorption technique Soils were amended with the bacterial and fungal suspensions and extracted immediately with either DTPA or potassium sulfate and extracted Zn were measured Conversion factors of bacteria and fungi were calculated separately as 0 36 and 0 32 respectively The overall microbial biomass conversion factor was determined as 0 33 by using the bacterial and fungal contribution in soil microbial biomass On the average the soil microbial biomass Zn was evaluated about 48 of soil DTPA extractable Zn and 0 6 of soil total Zn Compared to DTPA less Zn was extracted when potassium sulfate was used as an extractant for fumigated and non fumigated soils No significant correlation was observed between two extraction procedures Exchangeable non exchangeable and total soils K were 2 6 5 1and 7 7 times greater than that of soil microbial biomass K The average of potassium to Zn concentration ratio in the soil microbial biomass was 201 and the two variables were significantly correlated r 0 65 P 0 05 A precise and accurate measurement protocol based on the fumigation extraction technique was developed for the calcareous soil Key Words Chloroform fumigation Extraction Zinc Potassium Microbial biomass

زارعي، پروين

تعيين مقدار روي توده زنده ميكروبي در گروهي از خاك هاي آهكي

تدخين-عصاره گيري , پتاسيم