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Release Pattern of Nh4+-n from Prilled Urea and Urea Super Granules Under Lowland Rice Cultivation

P. K. Saha
Senior Scientific Officer
Soil Science Division, BRRI, Gazipur-1701

M. A. Mazid Miah
Chief Scientific Officer and Head
Soil Science Division, BRRI, Gazipur-1701

M. S. Rahman
Senior Scientific officer
Soil Science Division, BRRI, Gazipur-1701

A. Islam
Senior Scientific officer
Soil Science Division, BRRI, Gazipur-1701

Abstract/ Executive Summary:

A field experiment was carried out at the Bangladesh Rice Research Institute (BRRI) Farm, Gazipur to study the release pattern of NH₄⁺-N from two sources of N viz., prilled urea (PU) and urea super granules (USG) at different N levels under lowland situation. It appeared from the findings that at N₀ (with no N fertilizer) plots, NH₄⁺-N concentration increased from 9.03 (initial) to 16.58 mg/kg at 15 days after transplanting (DAT), and then gradually decreased throughout the growing season. At 90 DAT it dropped below the initial value. At 15 DAT the plots, in which PU at different doses (N₁₀₀-N₁₅₀) were added, showed a significant positive increase of NH₄⁺-N by 5.31-5.88 mg/kg over N₀ plots. However, no significant difference in NH₄⁺-N concentration was observed among N added plots. At 45 DAT, it was observed that the magnitude of release pattern of NH₄⁺-N from USG was slightly higher than that of PU. A tendency of releasing more NH₄⁺-N was observed with the highest doses of PU and USG compared to lower doses at 45 DAT. The amount of released NH₄⁺-N gradually decreased with time depending on the magnitude of the applied N levels. Results indicated that a basal dose of N fertilizer may not be required for the rice crop growing in the Grey-Terrace Soil of Madhupur Tract. Instead, N fertilizer may be used after 15 DAT, when the rice plants are established.

Keywords: Release pattern, NH4+-N, Urea super granules, Lowland rice

Location: Bangladesh Rice Research Institute (BRRI) experimental farm, Gazipur

Start Date: 01-11-1998

End Date: 30-06-1999

Program Area: Crop-Soil-Water Management

Commodity: Fertilizer

Objectives:

To determining the release pattern of NH₄⁺-N in situ from two sources of N fertilizer prilled urea (PU) and urea super granules (USG) with different N levels under wetland rice cultivation.

Methodology:

The field experiment was conducted at the BRRI farm, Gazipur in the Boro season, 1998-99. Soils of the experimental field is clay loan in texture and slightly acidic in nature having organic carbon 1.18%, total N 0.12%, C:N ratio 9.8, CEC 23 cmol/kg, NH₄⁺-N 9.03 mg/kg and NO₃^--N 2.64 mg/kg. Field experiment was established with BRRI dhan29 rice variety using two sources of N: PU and USG. The N doses for PU were: 0, 100, 125 and 150 kg/ha and for USG were: 0, 81 and 109 kg/ha. Experiment was laid out in a RCB design with three replications. PU was applied as broadcast in four equal splits: 25% as basal, 25% at 15 days after transplanting (DAT), 25% and 45 DAT and 25% at 90 DAT. All USG was applied one time at 15 DAT in deep placement method when rice plants were established. Initial soil samples (0-20 cm depth) were from 15 spots of each block of the main field prior to fertilizer application. After transplanting, samples (0-20 cm depth) from the three spots of each designated plots were collected to determine in situ N mineralization according to schedule: initial and 1^st soil sampling, basal N application and seedling transplanting on 3^rd January 1999 (0 DAT); 2^nd soil sampling, 1^st PU top dressing and USG application on 18^th January 1999 (15 DAT); 3^rd soil sampling and 2^nd PU top dressing on 17^th February 1999 (45 DAT); 4^th soil sampling and 3^rd PU top dressing on 3^rd April 1999 (90 DAT). Soil sampling was done before N fertilizer (PU and USG) application. About 200 g composite fresh soils were collected in a plastic bag. Inorganic NH₄⁺-N was determined from the fresh soil samples and considered as the N availability index for submerged soil. At each specified time, after the collection of samples from experimental field, 20 g composite fresh soil was weighed and taken into a 125 ml conical flask and 100 ml of 2M KCl added, capped and shaken for two hours on a reciprocating shaker. Samples were filtered though Whatman No. 42 filter paper. At the same time determination of moisture of soil was done to adjust the results in an oven dry basis. Inorganic NH₄⁺-N was determined by Micro kjeldahl distillation method (Keeney and Nelson, 1982).

Source of Information: Bangladesh J. Agril. Res. 15 (2): 261-267, June 2008

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Nitrogen fertilization either as PU or USG increased soil N mineralization (NH₄⁺-N) during the growing period of wetland rice. The NH₄⁺-N concentration at N₀ plots significantly increased from 9.03 (initial) to 16.58 mg/kg at 15 DAT and then gradually decreased with time throughout the growing period and at 90 DAT, it decreased sharply. Applied N significantly increased the NH₄⁺-N concentration in soil by 5.31-5.88 mg/kg over N₀ plots at 15 DAT. However, no significant difference in NH₄⁺-N concentration was observed among N added plots. In the early growth stage, plots receiving low amount of applied N (N₁₀₀) released slightly more NH₄⁺-N than that of higher N doses plots. At 45 DAT, N fertilized with the highest doses of PU and USG plots released more NH₄⁺-N than did N fertilized with the lower doses plots. Superiority was found with the plots receiving highest doses of USG (N₁₀₆-N₁₀₉). Statistically, the difference was at par compared to the plots receiving N₁₀₀-N₁₅₀ from PU. The amount of released NH₄⁺-N gradually decreased with time depending on the magnitude of the applied N levels. The release pattern of NH₄⁺-N at 45 DAT was higher from the USG source compared to PU. At 90 DAT, the amount of NH₄⁺-N at the different levels dropped below the initial value.

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