An experiment was conducted at the Soil Science Field Laboratory of Bangladesh Agricultural University, Mymensingh during boro season of 2014 to evaluate the effect of deep placement of nitrogen (N) fertilizers on N use efficiency and yield of BRRI dhan29 under flooded condition. The soil was silt loam in texture having pH 6.27, organic matter content 1.95%, total N 0.136%, available P 3.16 ppm, exchangeable K 0.095 me%, available S 10.5 ppm and EC 348 μS cm -1 . . All the treatments except T 6, T 7 and T 8 received 25 kg P and 64 kg K ha -1 as TSP and MoP respectively. In T 6, T 7 and T 8 treatments, P and K were supplied from NPK briquettes. Prilled urea was applied in three equal splits. USG and NPK briquettes were applied at 10 DAT and were placed at 8-10 cm depth within four hills at alternate row. After deep placement of USG and NPK briquette, and each split application of PU, the water samples were collected for 5 consecutive days and analyzed for NH 4 -N concentration in surface water. After application of N fertilizers, the NH 4 -N in floodwater reached peak on the 2 nd day in PU treated plots and then decreased rapidly over time. In the USG and NPK briquette treated plots, the NH 4 -N was generated slowly but spontaneously over the entire growth period as compared to PU indicating a beneficial role of USG and NPK briquette.

Although urea placed deep reduces nitrogen (N) loss and increases rice yield, its use is not expanding due to the lack of effective application methods. A study was carried out to determine how different urea application techniques affected the yield and nitrogen use efficiency (NUE) of transplanted Aman rice (cv. BRRI dhan46). The experiment was set up in a RCBD design with seven treatments: T1 (deep placement of urea briquettes (DPUB) by hand), T2 (DPUB by battery-powered applicator), T3 (deep placement of prilled urea (PU) briquettes by BRRI applicator), T4 (DPUB by injector applicator), T5 (DPUB by push-type applicator), T6 (broadcast application of PU), T7 (zero-N), and three replications. Findings showed that the NH4+-N concentration in field water peaked on day 3 and then rapidly fell as time passed, while the NO3−-N concentration in the water and soil was minimal. T1 reported the highest grain yield, total N content and uptake, whereas T7 had the lowest values. On T1, the apparent N recovery reached its highest level (73.5%). The NUE varied from 13.26% in T3 to 29.38% in T1. Based on this finding, deep placement of urea briquette by hand is recommended for increasing the yield and NUE of T. Aman rice.