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Pakistan Journal of Biological Sciences
Year: 2004  |  Volume: 7  |  Issue: 6  |  Page No.: 1029 - 1036

Genotypic Differences in Nitrogen Uptake and Utilization of Wet and Dry Season Rice as Influenced by Nitrogen Rate and Application Schedule

B.C. Roy, D.E. Leihner, T.H. Hilger and N. Steinmueller    

Abstract: Nitrogen accumulation, uptake and use efficiency of wet and dry season varieties were determined from field experiments conducted in 1996 to 1998 at the Bangladesh Rice Research Institute (BRRI) in Gazipur, Bangladesh. Four rice varieties were tested, Nsail and BR31 were planted in the wet season (WS) and HB6 and BR29 were planted in the dry season (DS). Nsail and HB6 are local, whereas BR31 and BR29 are modern varieties. The experiments were laid out in a two-factorial randomized complete block design with four replications. The two factors were nitrogen rate and its application schedule. Four N rates-0, 50, 100 and 150 kg N ha-1 were given. The rates of 50, 100 and 150 kg N ha-1 were given in three application schedules-two, three and four splits. Transplanting was done on the first week of August and first week of January for the WS and DS, respectively. Nitrogen uptake differed greatly among the varieties and nitrogen rates. The increase of total N uptake with N rate was almost linear for the modern varieties, whereas the traditional varieties showed a quadratic relationship between total N uptake and N level. Effect of N split application on N uptake was small, but the difference among the split applications were more pronounced when higher amont of N was applied. Genotypic difference in grain and straw N concentration of all the varieties was observed and increased with each increment of N fertilizer. Averaged across treatments and years, the highest grain N concentration was observed in BR31 and the lowest in BR29. The straw N concentration at different N rates were more pronounced in the wet season varieties, especially Nsail, which had the lowest straw N concentration when no N was applied but showed highest straw N concentration when 150 kg N ha-1 was applied. The agronomic fertilizer efficiency and the apparent N recovery percentage varied greatly among the varieties and decreased with higher N rates. The agronomic efficiency of the DS varieties was higher compared to the WS varieties. Across the years, the N recovery percentage of the tested varieties at different N rates and application schedules ranged from 20 to 40% for Nsail, 24 to 43% for BR31, 29 to 40% for HB6 and 35 to 51% for BR29.

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