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Extraction and Characterization of Earthworm Cast and Adjoining Soil Humus at Low Temperature

M. N. Pramanik
Teachers' Training College, Rajshahi, Bangladesh

M.S. Jahan
Department of Zoology, Rajshahi University, Bangladesh

S. Hoque
Department of Soil, Water & Environment, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

A study was conducted to investigate the influence of refrigerator temperature (4⁰C) on the extraction of humic substances from earthworm cast of different origin and bulk soil and a comparison was made between humus of earthworm cast and bulk soil in respect of some physical and chemical characteristics. On an average particle fraction, moisture content, pH and organic content of the soil increased by 19.19%, 14.68%, 7.90% and 20.17%, respectively through the casting activity of earthworms. The extractability of rural humus substances increased about 19% at low temperature regime. Humic acids (68%) in bulk soil and fulvic acid (26%) in earthworm cast were found out-extracted significantly (P<0.05). Extinction coefficient ratio (E4 :E6 ) in soil were found 6.071 ± 0.484 and 6.448± 0.766 at room temperature and refrigerator temperature, respectively, but in earthworm cast the values were 7.250±0.721 and 7.779±0.238, respectively, i.e., E4 :E6 ratio increased more in cast (7.297%) than soil (6.210%) due-to low temperature effect. Earthworm cast contained more humic acid than fulvic acid.

Keywords: Soil, Soil humus, Temperature, Organic carbon, Grassland, Compost pit, Paddy

Location: Teacher Training College, Rajshahi, Bangladesh

Start Date:

End Date:

Program Area: Socio-economic and Policy

Non-commodity: Performance

Objectives:

To optimize and rapid extraction of humus substances than the previous methods by physical means through low temperature regime treatment

Methodology:

Casts of Glyphidrilus tuberosus, Polypheretima elongata , Eutyphoeus orientalis, and Metaphire posthuma and their surrounding soils were collected from paddy field, fallow l and grassland and compost pit, respectively, with three replications. The collected samples (300 g of each) were air dried and grinded in a wooden mortar and pestle so that the particles do not break. Then the samples were sieved through a 1-mm mesh sieve after dispersion with calgon to find out the <1 mm fraction percentage. Moisture percentage was determined. pH was determined in a 1:2.5 soil: water suspension using a glass electrode pH metter. For the extraction of humus substances the <2 mm fractions were finely ground in an agate mortar and passed through a 0.15 mm meshed sieve (Enoecottis, Filter Ltd, London England). Total organic carbon was determined by slight modification of Tyurin's method as described and the values were multiplied by 1.724 for the estimatin of total organic matter. Humus substances were extracted from the samples keeping under room temperature (6+2⁰C) for 12 hours and in a regrigerator temperature (4⁰C) i.e. low temperature regime for 8 hours. From the extract humic and fulvic acids were estimated. The optical density, especially the E4/E6 ration for humic substances were determined by Chemita Visible Spectrophotometer (Type CL 10-A4) at 465 and 665 m wavelengths.

Source of Information: Bangladesh J. Soil Sci. 36(1-2): 53-57, 2010

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The effect of temperature on the extinction coefficient ratio (E4 : E6) values are presented which indicated that the average E4 : E6 ratio increased from 6.21% in soil to 7 .30% in the cast due to low temperature effect though there was no statistical significant difference. The E4 : E6 ratio is independent of the concentration of carbon in solution and is a characteristic of humic acids from different soil types. A higher value, 7 to 8 or more were usually observed for fulvic acid or humic acid fractions with relatively low molecular weight but a lower value, about 3-5 are noted for humic acid and other related compounds with high molecular weights. The E4 : E6 ratio values in the present study indicated that in soil samples the humic acids and other related compounds with high molecular weight were increased by condensation in the aromatic nets of carbon atom in the humic acid and the aliphatic side chain decreases due to low temperature effect but in cast the fulvic acids and other humic fractions of low molecular weight are out-extracted under low temperature regime. It was pointed out that generally the molecular weight of humic acid was higher than the fulvic acid and there was a tendency for fulvic acid to move more easily than humic acid. The E.4 : E6 ratio was inversely related with particle weight and volume, which also supports the present findings. Since the samples were of different origin and the extinction coefficient ratio values were unable to draw perfect conclusion about the structure and function of the compounds, it requires further study on the spectroscopic and other modern sophisticated techniques for characterization of the compounds extracted in excess under low temperature regime.

Knowledge Management: Journal