Yield Response of Broadcast Aus Rice (Oryza sativa L.) to Nitrogen Variations in Southwestern Coastal Region of Bangladesh

Abstract

Cropping in the southwestern (SW) coastal region of Bangladesh is completely different from that of other parts of the country. Generally, Fallow–Fallow–Transplanted (T.) Aman is the dominant cropping pattern; thus, a vast area remains fallow during the Rabi and Kharif-I seasons. A new cropping pattern is emerging by incorporating Broadcast (B.) Aus rice during early summer (Kharif-I), before the monsoon-season T. Aman crop, but the fertilizer requirement, particularly nitrogen (N), is not clearly defined. The present field study was conducted with Broadcast Aus rice (var. BRRI dhan48) in a typical coastal soil at Pankhali, Dacope, Khulna, a saline area of Agro-Ecological Zone (AEZ) 13. There were six nitrogen treatments: 0, 35, 52, 70, 87, and 104 kg N ha⁻¹. Nitrogen rates had statistically significant effects on plant height, grain yield, straw yield, yield attributes (panicle length, number of grains panicle⁻¹, number of panicles m⁻², and number of filled grains panicle⁻¹), and harvest index. At harvest, the highest tiller number (6.7), panicle length (19.3 cm), number of grains panicle⁻¹ (85.5), number of panicles m⁻² (462.3), number of filled grains panicle⁻¹ (72.1), 1000-grain weight (22.8 g), and grain yield (3.9 t ha⁻¹) were produced by the application of 70 kg N ha⁻¹. Grain yield did not increase significantly with nitrogen application beyond 70 kg N ha⁻¹. The lowest values of almost all parameters were recorded in the treatment without nitrogen application. The findings of the experiment revealed that 70 kg N ha⁻¹ may be recommended for achieving maximum grain yield of Broadcast Aus rice in the southwestern coastal region of Bangladesh.