Understanding the factors controlling nitrogen use efficiency (NUE) in paddy soil is essential for optimizing the application of relatively costly nitrogen (N) fertilizer for rice cultivation. Therefore, an experiment was conducted to assess the seasonal variation in NUE among three Aus, five Aman, and three Boro rice varieties at the Bangladesh Agricultural University (BAU) farm during the Aus, Aman, and Boro cropping seasons. In addition, the variation in the NUE of rice was assessed among eight soil series throughout Bangladesh during the Boro season. The experiment included N control and N application at the recommended rates. The results showed that BRRI dhan48 outperformed the other varieties in the Aus season, with the maximum agronomic efficiency (AE). In contrast, BRRI dhan65 was better in terms of physiological efficiency (PE), whereas BRRI dhan42 showed the lowest AE. Throughout the Aman period, BR11 exhibited the best AE and PE. During the Boro season, BRRI dhan29 and BINA dhan-6 demonstrated the maximum AE, PE, and apparent recovery efficiency (ARE). Grain yield, nitrogen response, AE, and ARE were markedly higher in the Boro season than in the Aus and Aman seasons. Among the eight locations, the highest grain yield of BINA dhan-7 in the Aman season was recorded in the Noadda soil series, followed by Barisal and Sara, with an AE extended from 11 to 19 kg grain kg/N applied, PE from 31 to 61 kg grain kg/N uptake, and ARE from 21% to 41%. These findings highlight the significant variability in NUE among rice varieties, seasons and soil series, suggesting the importance of variety, location and season-specific N management.
Hossain et al. (Thu,) studied this question.