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A Study of Availability of Soil Nitrogen by Various Extractants

A. K . M. A. Hossain
Department of Soil Science, Dhaka University, Bangladesh

S. Hoque
Department of Soil Science, Dhaka University, Bangladesh

R. Mandal
Department of Soil Science, Dhaka University, Bangladesh

T. H . Khan
Department of Soil Science, Dhaka University, Bangladesh

A. S. Howlader
Department of Soil Science, Dhaka University, Bangladesh

A. Islam
Department of Soil Science, Dhaka University, Bangladesh

Abstract/ Executive Summary:

Available nitrogen was determined using 11 extractants on 29 soils covering a wide range of physical and chemical properties. Assessment of 2M KCI (pH 7.0), 1 N NaCI, 1N NaCI (pH 1.0), 2N NaCI, 1N Na₂S0₄ (pH 1.0), 0.5 N NaHC0₃ (pH 8.5), Morgan's reagent, 0.1 N CaCiz, 0.5N HCI, 0.7N HCI and 0.5N H₂S0₄ extractable nitrogen showed that the best efficiency was obtained by 1 N NaCI. IN NaCI and 2M KCI extractable nitrogen bear significant relationship with soil organic matter and total nitrogen were found to be dependent on the type of soil. Correlation study with nitrogen uptake by BR-4 rice reveals that 2M KCI is superior to 1N NaCl and closely followed by 1N NaCI. Compared to these two extractants both aerobic and anaerobic incubation methods produced less satisfactory result.

Keywords: Soil, Nitrogen, Plant uptake, Greenhouse

Location: Various localities of Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Soil fertility

Objectives:

To find out a suitable method for deter mining available N from 29 soils of Bangladesh by chemical extraction, shortterm incubation and plant uptake in the greenhouse

Methodology:

Twenty nine soil samples ( 0-1 5 cm) under 13 General Soil Type representing different soil series were collected from various localities of Bangladesh. The soil samples were processed and analyzed in the laboratory for their physical and chemical characteristic. Determinations were made of particles-sized distribution by hydrometer method, pH with a combined glass/calomel electrode (soil : water, I : 2.5), total N by Kjeldahl method, organic C by wet oxidation met hod and CEC by nor mal ammonium acetate (pH 7.0 ). Available N was determined following micro-Kjeldahl's distillation procedure. Eleven extractants covering various; acids, bases and buffered solutions have been used to test for availability. The soil: extractant ratio was I : 10 and the extraction period was 30 minutes. Only for 2M KCI extractant the extraction time was 6o minutes. 3 kg air dry soil (2 mm) was taken in each earthen ware pot (1 8 cm x 22 cm). Polyethelene film was used between soil and pot to a void contamination from the earthen ware pots. Soils in each pot was kept submerged for three days for complete wetting. Four week old healthy rice (Oryw salira cv. BR-4) seedling's of uniform size was transplanted (four seedlings/pot) at a regular distance. About 2 - 3 cm level of standing water was maintained throughout the whole experimental period. The experiment was arranged in randomized block design with three replications. 20 g air-dried sample (2 mm) fro m each soil was weighed into 100 ml conical flask. Water was added in each conical flask to bring into 50% maximum water holding capacity and mixed thoroughly. The flasks were plugged with absorbent cotton and incubated at 30 ±0.5. The experiment was arranged in a randomized block design with two replications. Samples in duplicate were collected from each flask after 15 days of incubation to determine available nitrogen and moisture. Available nitrogen was extracted by 1 N NaCI. Plant samples were digested with cone. H 2S0₄ and mixture of cone. H₂S0₄. and HCl0₄ (4: l, v/v). Total nitrogen of soil and plant was determined by Kjeldahl method.

Source of Information: The Bangladesh Journal of Scientific Research, Vol. – 7, No. – 1, June – 1989

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Concentration of available nitrogen was determined from 29 soils by 11 extractants. The quantity of nitrogen extracted by different extractants have been found to differ widely. Content of nitrogen varied between 0.7 ( Pirgachha) and 15.5 mg l00 -1g soil (Sonatala) irrespective of the methods of extraction. Assessment of 2M KCI (pH 7.0), 1 N NaCI, 1N NaCI (pH 1.0), 2N NaCI, 1N Na2S04 (pH 1.0), 0.5N NaHC0₃ (pH 8.5 ), Morgan's reagent, 0.1N CaCiz, 0.5N HCI, 0.7N HCI and 0.5N H₂S0₄ extractable nitrogen showed that the best efficiency was obtained by 1N NaCI. IN NaCI and 2M KCI extractable nitrogen bear significant relationship with soil organic matter and total nitrogen were found to be dependent on the type of soil. Correlation study with nitrogen uptake by BR-4 rice reveals that 2M KCI is superior to 1N NaCl and closely followed by IN NaCI. Compared to these two extractants both aerobic and anaerobic incubation methods produced less satisfactory result.

Knowledge Management: Journal