Rice husk-biochar nano-carrier based 2, 4-D herbicide for efficient management of broad leaf weeds and sedges

Rice husk (RHNC) and rice husk biochar (RHBNC) nano-carriers were evaluated for enhancing the bio-efficacy of 2,4-D herbicide. Nano-carriers were synthesized by planetary ball milling and loaded with 2,4-D at two weight ratios (1:0.25 and 1:0.10). Structural characterization was carried out using SEM, FT-IR, XRD, BET surface area, and BJH pore volume analysis. SEM images of ball-milled rice husk biochar revealed a porous structure with cracks and shrinkage, while FT-IR confirmed the presence of aromatic, carbonyl, and siloxane groups. XRD spectra of RHBNC displayed a broadened peak at 45° (2θ). BET analysis indicated reduced surface area (9.85 m² g⁻¹) and pore volume (0.043 cm³ g⁻¹) after herbicide loading. Bio-efficacy was assessed against Limnocharis flava and Cyperus rotundus in pots, followed by a field trial in upland rice. RHBNC (1:0.25) at 0.8 kg ha⁻¹ exhibited the highest weed control efficiency (95.33 % in purple nutsedge and 98.74 % in water cabbage) and significantly improved rice yield (2840 kg ha⁻¹), representing a 21 % increase over conventional 2,4-D. Enhanced soil biological activity was also observed, with higher dehydrogenase activity (31.70 µg TPF g⁻¹ soil d⁻¹) and bacterial counts (52.00 × 10⁶ CFU g⁻¹ wet soil) compared to conventional treatments. These results prove the efficacy of rice husk biochar as a good and ecofriendly nano-carrier of 2,4-D, providing enhanced weed control, crop yields, and soil microbial well-being.