Field experiments were conducted during 2021 and 2022 with twelve treatments on sandy clay loam soil in randomized block design (RBD), replicated thrice. The treatment consisted of rice co-culture with Sesbania bispinosa (Sesbania) and applied with different formulations of 2,4-D sodium salt, ethyl-ester and amine at varied levels (0.50, 0.75 and 1.0 kg/ha), hand weeding twice, weed free and unweeded control. Application of 2,4-D ethyl-ester 1.0 kg/ha proved effective in weed management by exhibiting significantly lower densities of grass (70.7/m2), sedges (14.7/m2), and broad-leaved weeds (0.0/m2) with higher weed control efficiency of 74.3%  at 60 DAS. Brown manuring through application of 2,4-D ethyl-ester 1.0 kg/ha led to higher grain yield (3.62 t/ha) and B:C ratio (2.03) and it was followed by 2,4-D sodium salt 1.0 kg/ha. Therefore, 2,4-D ethyl-ester 1.0 kg/ha can be recommended for effective brown manuring and eco-friendly weed management in rice, which would provide higher rice grain yield and B: C ratio. The next best treatment was rice co-culture with dhaincha and applied with 2,4-D sodium salt 1.0 kg/ha in wet seeded rice of deltaic coastal ecosystem.