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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 KCl (pH 7.0), 1N NaCl, 1N (pH 1.0), 2N NaCl, 1N NaSO₄ (pH 1.0), 0.5N NaHCO₃ (pH 8.5), Morgan’s reagent, 0.1N CaCl₂, 0.5N HCl, 0.7N HCl and 0.5N H₂SO₄ extractable nitrogen showed that the best efficiency was obtained by 1N NaCl. IN NaCl and 2M KCl 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 BR4 rice reveals that 2M KCl is superior to 1N NaCl and closely followed by IN NaCl. Compared to these two extractants both aerobic and anaerobic incubation methods produced less satisfactory results.

Keywords: Soil nitrogen, Extractants, Incubation period, Green house

Location: Dhaka, University

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Fertilizer

Objectives:

To find out a suitable method for determining available N from 29 soils of Bangladesh by chemical extraction, short-term incubation and plant up take in the greenhouse.

Methodology:

Twenty nine soil samples (0-15) under 13 General Soil Types representing different soil series were collected from various localities of Bangladesh. The soil samples were processed and analysed in the laboratory for their physical and chemical characteristics. Determinations were made of particle-size distribution by hydrometer method, pH with a combined glass/calomel electrode (soil: water, 1: 2.5), total N by Kjeldahl method, organic C by wet oxidation method (walkley and black, 1934), and CEC by normal 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 taste for N availability. The soil : extractant ratio was 1 : 10 and the extraction period was 60 minutes. Extractants used were 2M KCl (Olsen, 1929); 1N NaCl (Hissink, 1923); 1N NaCl (pH 1.0) (Oslen, 1929); 2N NaCl ( Bremner and shaw, 1955); 1N NaSO₄ (pH 1.0); 0.5M NaHCO₃ (pH 8.5) (oslen et al. , 1954); Morgan’s reagent (10% CH₃COOH, pH 4.8) (Morgan, 1937); neutral 0.01m CaCl₂ (Lathwell et al., 1972); 0.5N HCl (Peterson et al., 1960); 0.7N HCl (Peterson et al., 1960); 0.5N H₂SO₄. (Tyurin, 1934; Tyurin and Kononova, 1934), Dil HCl was used to adjust the pH of 1N NaCl and 1N Na₂SO₄ solution. Each sample was measured in duplicate but only the mean results were quoted (Table 1&2). Greenhouse experiment: 3 Kg air dry soil (2 mm) was taken in each earthenware pot (18 cm x 22 cm). Polyethelene film was used between soil and pot to avoid contamination from the earthenware pots. Soils in each pot were kept submerged for three days for completing wetting. Four week old healthy rice (Oryza sativa cv. BR-4) seedlings 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 experiment period. The experiment was arranged in randomized block design with three replications. One plant sample was collected randomly from each pot by cutting 8 cm above the soil surface after 30, 60 and 90 days of transplantation. The plant samples were then washed with distilled water followed by oven drying for 16 hours at 65 ±1C and ground to 1 mm size in a microgrinder. Incubation experiment: 20 g air-dried sample (2 mm) from each soil was weighed into 100 ml conical flask. Water was added in each 100 ml 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 (5g) in duplicate were collected from each flask after 15 days of incubation to determine available nitrogen and moisture. A similar experiment was carried out under anaerobic condition where the soil samples were kept submerged (2-3 cm standing water) during incubation period. The flasks were covered with polyethelene paper. Soil samples were analyzed for available nitrogen and moisture content after 28 days (Ponnamperuma, 1965) of incubation.

Source of Information: Bangladesh J. Sci. Res. 7(1): 1989, 51-60

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Assessment of 2M KCl (pH 7.0), 1N NaCl, 1N (pH 1.0), 2N NaCl, 1N NaSO₄(pH 1.0), 0.5N NaHCO₃ (pH 8.5), Morgan’s reagent, 0.1N CaCl₂, 0.5N HCl, 0.7N HCl and 0.5N H₂SO₄ extractable nitrogen showed that the best efficiency was obtained by 1N NaCl. IN NaCl and 2M KCl 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 BR4 rice reveals that 2M KCl is superior to 1N NaCl and closely followed by IN NaCl. Compared to these two extractants both aerobic and anaerobic incubation methods produced less satisfactory results.

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