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Nitrogen Management for Over-aged Seedlings of Short Duration Variety in Aman Season

B C Roy
SSO
Agronomy Division, BRRI, Gazipur

J C Biswas
SSO
Agronomy Division, BRRI, Gazipur

G.J.U Ahmad
CSO
Agronomy Division, BRRI, Gazipur

Abstract/ Executive Summary:

The experiments were conducted at Bangladesh Rice Research Institute (BRRI), Gazipur during Aman season of 2005 and 2006. The influence of N rate (80 and 120 kg ha^-1) and its management was investigated with variable seedling ages (20, 40 and 60 day-old) of BRRI dhan33, a short duration variety. Heading of mother plants was observed at 7-10 days after transplanting (DAT) for 60 day-old seedlings and heavy application of N fertilizer at that stage reverted the reproductive phase to vegetative phase and initiated new tillers. Grain number per unit area decreased by 22-25% with 60 day-old seedlings compared to 20 day ones following BRRI recommended N rate and application schedule. But when 120 N/ha was applied, of which 2/3rd at 7-10 DAT and 1/3rd at panicle initiation (PI) stage was applied, grain number reduction was only 11%. Spikelet sterility was higher with over-aged seedlings. The highest grain and straw yields were obtained from 20 day-old seedlings and the least from 60-day old seedlings when BRRI recommended N application schedule was followed. The modified N rate and its application schedule increased grain and straw yields of 60 day-old seedlings by 15 and 22%, respectively. Eighty kg N ha^-1 at 7-10 DAT and 40 kg N ha^-1 at PI stage could be suitable application schedule for older seedlings to get comparatively satisfactory grain yield in Aman season.

Keywords: Nitrogen management, Over-aged seedlings, Short uuration variety, Aman season

Location: BRRI, Gazipur-1701

Start Date: 01-06-2005

End Date: 31-12-2006

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To find out suitable N rate and application schedules for satisfactory grain yield with over-aged seedlings of short duration variety in Aman season.

Methodology:

The study was conducted at BRRI, Gazipur during Aman season of 2005 and 2006. BRRI dhan33, a short duration variety having 118 days growth duration was used. Soil properties were Aeric heplaquept with silty clay texture, pH 6.5, total N 0.08 %, organic carbon 0.73 %, available P 9 ppm, exchangeable K 19 meq/100 g soil. The influence of 20, 40 and 60 day-old seedlings were tested with 80 and 120 kg N/ha. Nitrogen was applied in two or three splits at different times after transplanting (DAT). The treatment combinations were: i) 20 day-old seedling + 80 kg N ha^-1applied thrice equally at basal, 15 days after transplanting (DAT) and 5 days before panicle initiation (DBPI) stage (T1); ii) 40 day-old seedling + 120 kg N ha^-1 applied thrice equally at basal, 15 DAT and 5 DBPI (T2); iii) 60 day-old seedling + 120 kg N ha^-1 applied equally at basal, 15 DAT and 5 DBPI (T3); iv) 40 day-old seedling + 120 kg N/ha applied thrice, 2/3d at basal and 1/3r^d at PI (T4) and v) 60 day-old seedling + 120 kg N/ha applied 2/3`d at 7-10 DAT and 1/3rd at PI (T5). The treatments were assigned in a randomized complete block design with three replications.

Two to three seedlings/hill of BRRI dhan33 at per treatment was transplanted on 7 and 15 August in 2005 and 2006, respectively. The transplanting was done maintaining 25 hills m^-2. Fertilizers other than N were 27, 33 and 10 kg ha^-1 P, K and S, respectively. Insects and weed management was done as and when necessary. Data on plant height, panicle number per square meter, grain number per panicle and per square meter, sterility percentage, grain yield and straw yields were collected. Grain yields were adjusted at 14% moisture content. Data were analyzed statistically (Gomez and Gomez, 1984). Pooled analysis on grain yields was done to find out treatment effects over years.

Source of Information: Bangladesh Rice J. 12 (1 & 2) : 111-114, 2007

Article Link (Online Journal):

Funding Source:

1. Government

Budget: 50,000/-

Total Budget (Tk.) : 50,000/-

Achievement/Findings:

The highest grain and straw yields were obtained from 20 day-old seedlings and the least from 60-day old seedlings when BRRI recommended N application schedule was followed. The modified N rate and its application schedule increased grain and straw yields of 60 day-old seedlings by 15 and 22%, respectively. Eighty kg N ha^-1 at 7-10 DAT and 40 kg N ha^-1 at PI stage could be suitable application schedule for older seedlings to get comparatively satisfactory grain yield in Aman season.

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